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97-557: Cryptochromes (from the Greek κρυπτός χρώμα, "hidden colour") are a class of flavoproteins found in plants and animals that are sensitive to blue light . They are involved in the circadian rhythms and the sensing of magnetic fields in a number of species. The name cryptochrome was proposed as a portmanteau combining the chromatic nature of the photoreceptor , and the cryptogamic organisms on which many blue-light studies were carried out. The genes CRY1 and CRY2 encode

194-525: A 2021 study, metabolic outputs , measured by bowel movements , were severely different for participants who were wild type in comparison to those with the CRY1Δ11 variant. The participants with the variant had a delayed sleep cycle and delayed metabolic output when compared to the wild type. Magnetoreception is a sense which allows an organism to detect a magnetic field to perceive direction, altitude or location. Experimental data suggests that cryptochromes in

291-570: A basis for coinages: anthropology , photography , telephony , isomer , biomechanics , cinematography , etc. Together with Latin words , they form the foundation of international scientific and technical vocabulary ; for example, all words ending in -logy ('discourse'). There are many English words of Greek origin . Greek is an independent branch of the Indo-European language family. The ancient language most closely related to it may be ancient Macedonian , which, by most accounts,

388-436: A circadian role upstream of other clock genes and components. In mammals, cryptochrome proteins are encoded by two genes, Cry1 and Cry2. Cryptochrome is one of the four groups of mammalian clock genes/proteins that generate a transcription-translation negative-feedback loop (TTFL), along with Period (PER) , CLOCK , and BMAL1 . In this loop, CLOCK and BMAL1 proteins are transcriptional activators , which together bind to

485-494: A conserved domain with deoxyribodipyrimidine photolyase , and positions 288 through 486 show a conserved domain with the FAD binding domain of DNA photolyase. Comparative genomic analysis supports photolyase proteins as the ancestors of cryptochromes. However, by 1995 it became clear that the products of the HY4 gene and its two human homologs did not exhibit photolyase activity and were instead

582-552: A fairly stable set of consonantal contrasts . The main phonological changes occurred during the Hellenistic and Roman period (see Koine Greek phonology for details): In all its stages, the morphology of Greek shows an extensive set of productive derivational affixes , a limited but productive system of compounding and a rich inflectional system. Although its morphological categories have been fairly stable over time, morphological changes are present throughout, particularly in

679-556: A faster, more convenient cursive writing style with the use of ink and quill . The Greek alphabet consists of 24 letters, each with an uppercase ( majuscule ) and lowercase ( minuscule ) form. The letter sigma has an additional lowercase form (ς) used in the final position of a word: In addition to the letters, the Greek alphabet features a number of diacritical signs : three different accent marks ( acute , grave , and circumflex ), originally denoting different shapes of pitch accent on

776-546: A few primary leaves with a flower. A double loss-of-function mutation in Arabidopsis thaliana Early Flowering 3 (elf3) and Cry2 genes delays flowering under continuous light and was shown to accelerate it during long and short days, which suggests that Arabidopsis CRY2 may play a role in accelerating flowering time during continuous light. Cryptochromes receptors cause plants to respond to blue light via photomorphogenesis . They help control seed and seedling development, as well as

873-531: A foreign language. It is also often stated that the historical changes have been relatively slight compared with some other languages. According to one estimation, " Homeric Greek is probably closer to Demotic than 12-century Middle English is to modern spoken English ". Greek is spoken today by at least 13 million people, principally in Greece and Cyprus along with a sizable Greek-speaking minority in Albania near

970-463: A ground state of FAD •. Researchers have also recently proposed a model in which FAD is excited to its doublet or quartet state by absorption of a photon, which then leads to a conformational change in the CRY protein. Also the ring eyes of the demosponge larva of Amphimedon queenslandica express a blue-light-sensitive cryptochrome (Aq-Cry2), which might mediate phototaxis. In contrast,

1067-400: A light response in opsin -knockout Drosophila . Cryptochrome, like many genes involved in circadian rhythm, shows circadian cycling in mRNA and protein levels. In Drosophila , Cry mRNA concentrations cycle under a light-dark cycle (LD), with high levels in light and low levels in the dark. This cycling persists in constant darkness (DD), but with decreased amplitude. The transcription of

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1164-625: A light source, in response to blue light. This response is now known to have its own set of photoreceptors, the phototropins . Unlike phytochromes and phototropins, cryptochromes are not kinases . Their flavin chromophore is reduced by light and transported into the cell nucleus , where it affects the turgor pressure and causes subsequent stem elongation. To be specific, Cry2 is responsible for blue-light-mediated cotyledon and leaf expansion. Cry2 overexpression in transgenic plants increases blue-light-stimulated cotyledon expansion, which results in many broad leaves and no flowers rather than

1261-429: A mediator of light sensitivity, significantly drops. In recent years, data have supported melanopsin as the main circadian photoreceptor, in particular melanopsin cells that mediate entrainment and communication between the eye and the suprachiasmatic nucleus (SCN). One of the main difficulties in confirming or denying CRY as a mammalian photoreceptor is that when the gene is knocked out the animal goes arrhythmic, so it

1358-399: A model by which energy captured by pterin is transferred to flavin. Under this model of phototransduction, FAD would then be reduced to FADH, which probably mediates the phosphorylation of a certain domain in cryptochrome. This could then trigger a signal transduction chain, possibly affecting gene regulation in the cell nucleus . A new hypothesis proposes that partner molecules sense

1455-427: A model in which the flavin cofactor exists in anion radical form, FAD •. Recently, researchers have observed that oxidized FAD is readily reduced to FAD • by light. Furthermore, mutations that blocked photoreduction had no effect on light-induced degradation of CRY, while mutations that altered the stability of FAD • destroyed CRY photoreceptor function. These observations provide support for

1552-538: A new class of blue light photoreceptor hypothesized to be circadian photopigments . In 1996 and 1998, Cry homologs were identified in Drosophila and mice , respectively. Cryptochromes (CRY1, CRY2) are evolutionarily old and highly conserved proteins that belong to the flavoproteins superfamily that exists in all kingdoms of life. Cryptochromes are derived from and closely related to photolyases, which are bacterial enzymes that are activated by light and involved in

1649-440: A pair of radicals with correlated spins when exposed to blue light. Radical pairs can also be generated by the light-independent dark reoxidation of the flavin cofactor by molecular oxygen through the formation of a spin-correlated FADH-superoxide radical pairs. Magnetoreception is hypothesized to function through the surrounding magnetic field's effect on the correlation (parallel or anti-parallel) of these radicals, which affects

1746-421: A photoreceptive role, as well as acting as negative regulators of Per gene expression in mice. In Drosophila , cryptochrome is only encoded by one Cry gene (d Cry) and functions as a blue light photoreceptor. Exposure to blue light induces a conformation similar to that of the always-active CRY mutant with a C-terminal deletion (CRYΔ). The half-life of this conformation is 15 minutes in the dark and facilitates

1843-403: A role in nonparametric entrainment (entrainment by short discrete light pulses). However, the lateral neurons receive light information through both the blue light CRY pathway and the rhodopsin pathway. Therefore, CRY is involved in light perception and is an input to the circadian clock, however it is not the only input for light information, as a sustained rhythm has been shown in the absence of

1940-612: A triad). The longer chain leads to a better separation and over 1000× longer lifetimes of the photoinduced flavin-tryptophan radical pairs than in proteins with a triad of tryptophans. The absence of spin-selective recombination of these radical pairs on the nanosecond to microsecond timescales seems to be incompatible with the suggestion that magnetoreception by cryptochromes is based on the forward light reaction. Greek language Greek ( Modern Greek : Ελληνικά , romanized :  Elliniká , [eliniˈka] ; Ancient Greek : Ἑλληνική , romanized :  Hellēnikḗ )

2037-527: Is a basic leucine zipper (bZIP) factor that promotes photomorphogenesis by binding to light-responsive genes. CRY interacts with G protein β-subunit AGB1, where HY5 dissociates from AGB1 and becomes activated. CRY interacts with PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) and PIF5, repressors of photomorphogenesis and promoter of hypocotyl elongation, to repress PIF4 and PIF5 transcription activity. Lastly, CRY can inhibit auxin and brassinosterioid (BR) signaling to promote photomorphogenesis. Despite much research on

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2134-605: Is a cofactor found in virtually all molybdenum and tungsten-containing proteins. It binds molybdenum to yield redox cofactors involved in biological hydroxylations, reduction of nitrate, and respiratory oxidation. Molybdopterin biosynthesis does not use the conventional GTPCH-1 pathway. It occurs in four steps: Tetrahydrobiopterin , the major unconjugated pterin in vertebrates, is involved in three families of enzymes that effect hydroxylation. The aromatic amino acid hydroxylases include phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylases. They are involved in

2231-766: Is also found in Bulgaria near the Greek-Bulgarian border. Greek is also spoken worldwide by the sizable Greek diaspora which has notable communities in the United States , Australia , Canada , South Africa , Chile , Brazil , Argentina , Russia , Ukraine , the United Kingdom , and throughout the European Union , especially in Germany . Historically, significant Greek-speaking communities and regions were found throughout

2328-742: Is an Indo-European language, constituting an independent Hellenic branch within the Indo-European language family. It is native to Greece , Cyprus , Italy (in Calabria and Salento ), southern Albania , and other regions of the Balkans , Caucasus , the Black Sea coast, Asia Minor , and the Eastern Mediterranean . It has the longest documented history of any Indo-European language, spanning at least 3,400 years of written records. Its writing system

2425-474: Is an Indo-European language, but also includes a number of borrowings from the languages of the populations that inhabited Greece before the arrival of Proto-Greeks, some documented in Mycenaean texts ; they include a large number of Greek toponyms . The form and meaning of many words have changed. Loanwords (words of foreign origin) have entered the language, mainly from Latin, Venetian , and Turkish . During

2522-463: Is delayed by approximately four hours relative to Cry1 promoter activation. This delay is independent of CRY1 or CRY2 levels and is mediated by a combination of E/E'-box and D-box elements in the promoter and RevErbA / ROR binding elements (RREs) in the gene's first intron. Transfection of arrhythmic Cry1 Cry2 double-knockout cells with only the Cry1 promoter (causing constitutive Cry1 expression)

2619-459: Is hard to measure its capacity as purely a photoreceptor. However, some recent studies indicate that human CRY1 may mediate light response in peripheral tissues. Normal mammalian circadian rhythm relies critically on delayed expression of Cry1 following activation of the Cry1 promoter. Whereas rhythms in Per2 promoter activation and Per2 mRNA levels have almost the same phase, Cry1 mRNA production

2716-453: Is not sufficient to rescue rhythmicity. Transfection of these cells with both the promoter and the first intron is required for restoration of circadian rhythms in these cells. There is evidence that CRY1 can play a role in how sleep-wake patterns can be inherited through families. There is a mutation, CRY1Δ11 , that causes a delay in one's circadian rhythm.  CRY1Δ11 is a splicing variant that has deleted an auto-inhibitory section of

2813-510: Is protected and promoted officially as a regional and minority language in Armenia, Hungary , Romania, and Ukraine. It is recognized as a minority language and protected in Turkey by the 1923 Treaty of Lausanne . The phonology , morphology , syntax , and vocabulary of the language show both conservative and innovative tendencies across the entire attestation of the language from the ancient to

2910-782: Is sometimes called aljamiado , as when Romance languages are written in the Arabic alphabet. Article 1 of the Universal Declaration of Human Rights in Greek: Transcription of the example text into Latin alphabet : Article 1 of the Universal Declaration of Human Rights in English: Proto-Greek Mycenaean Ancient Koine Medieval Modern Pterin Pterins were first discovered in

3007-471: Is spoken by at least 13.5 million people today in Greece, Cyprus, Italy, Albania, Turkey , and the many other countries of the Greek diaspora . Greek roots have been widely used for centuries and continue to be widely used to coin new words in other languages; Greek and Latin are the predominant sources of international scientific vocabulary . Greek has been spoken in the Balkan peninsula since around

Cryptochrome - Misplaced Pages Continue

3104-758: Is still used internationally for the writing of Ancient Greek . In Greek, the question mark is written as the English semicolon, while the functions of the colon and semicolon are performed by a raised point (•), known as the ano teleia ( άνω τελεία ). In Greek the comma also functions as a silent letter in a handful of Greek words, principally distinguishing ό,τι ( ó,ti , 'whatever') from ότι ( óti , 'that'). Ancient Greek texts often used scriptio continua ('continuous writing'), which means that ancient authors and scribes would write word after word with no spaces or punctuation between words to differentiate or mark boundaries. Boustrophedon , or bi-directional text,

3201-630: Is the Greek alphabet , which has been used for approximately 2,800 years; previously, Greek was recorded in writing systems such as Linear B and the Cypriot syllabary . The alphabet arose from the Phoenician script and was in turn the basis of the Latin , Cyrillic , Coptic , Gothic , and many other writing systems. The Greek language holds a very important place in the history of the Western world. Beginning with

3298-478: The Arabidopsis (6-4) photolyase protein. Based on the role of cryptochromes in the entrainment of mammalian circadian rhythms, current researchers hypothesize that they developed simultaneously with the coevolution of PER, TIM, CLOCK , and CYCLE proteins, but there is currently insufficient evidence to determine the exact evolution timing and mechanism of evolution. All members of the flavoprotein superfamily have

3395-755: The Cry gene also cycles with a similar trend. CRY protein levels, however, cycle in a different manner than Cry transcription and mRNA levels. In LD, CRY protein has low levels in light and high levels in dark, and, in DD, CRY levels increase continuously throughout the subjective day and night. Thus, CRY expression is regulated by the clock at the transcriptional level and by light at the translational and posttranslational level. Overexpression of Cry also affects circadian light responses. In Drosophila , Cry overexpression increases flies' sensitivity to low-intensity light. This light regulation of CRY protein levels suggests that CRY has

3492-486: The Eastern Mediterranean , in what are today Southern Italy , Turkey , Cyprus , Syria , Lebanon , Israel , Palestine , Egypt , and Libya ; in the area of the Black Sea , in what are today Turkey, Bulgaria , Romania , Ukraine , Russia , Georgia , Armenia , and Azerbaijan ; and, to a lesser extent, in the Western Mediterranean in and around colonies such as Massalia , Monoikos , and Mainake . It

3589-638: The G2/M checkpoint, and the depletion of CRY1 leads to effects on DNA repair networks, including mismatch repair, UV, and nucleotide excision . In cancer , CRY1 is stabilized by DNA damage, which results in CRY1 expression being associated with worse outcomes in prostate cancer . Because of its role in DNA repair and being pro-tumorigenic , further research can use CRY1 as a therapeutic target . Variants of CRY1 can have impacts on humans in regards to metabolic output. According to

3686-510: The Indo-Iranian languages (see Graeco-Aryan ), but little definitive evidence has been found. In addition, Albanian has also been considered somewhat related to Greek and Armenian, and it has been proposed that they all form a higher-order subgroup along with other extinct languages of the ancient Balkans; this higher-order subgroup is usually termed Palaeo-Balkan , and Greek has a central position in it. Linear B , attested as early as

3783-492: The nominal and verbal systems. The major change in the nominal morphology since the classical stage was the disuse of the dative case (its functions being largely taken over by the genitive ). The verbal system has lost the infinitive , the synthetically -formed future, and perfect tenses and the optative mood . Many have been replaced by periphrastic ( analytical ) forms. Pronouns show distinctions in person (1st, 2nd, and 3rd), number (singular, dual , and plural in

3880-647: The photoreceptor neurons of birds' eyes are involved in magnetic orientation during migration . Cryptochromes are also thought to be essential for the light-dependent ability of Drosophila to sense magnetic fields . Magnetic fields were once reported to affect cryptochromes also in Arabidopsis thaliana plants: growth behavior seemed to be affected by magnetic fields in the presence of blue (but not red) light. Nevertheless, these results have later turned out to be irreproducible under strictly controlled conditions in another laboratory, suggesting that plant cryptochromes do not respond to magnetic fields. Cryptochrome forms

3977-468: The promoters of the Cry2 and Per genes and activate their transcription. The CRY2 and PER proteins then bind to each other, enter the nucleus, and inhibit CLOCK-BMAL1-activated transcription. The overall function of CRY2 is therefore to repress transcription of CLOCK and BMAL1. Cry1 encodes the CRY1 protein which is a mammalian circadian photoreceptor. In mice, Cry1 expression displays circadian rhythms in

Cryptochrome - Misplaced Pages Continue

4074-461: The proteins CRY1 and CRY2, respectively. Cryptochromes are classified into plant Cry and animal Cry. Animal Cry can be further categorized into insect type (Type I) and mammal-like (Type II). CRY1 is a circadian photoreceptor whereas CRY2 is a clock repressor which represses Clock/Cycle (Bmal1) complex in insects and vertebrates . In plants, blue-light photoreception can be used to cue developmental signals. Besides chlorophylls , cryptochromes are

4171-687: The suprachiasmatic nucleus , a brain region involved in the generation of circadian rhythms, with mRNA levels peaking during the light phase and reaching a minimum in the dark. These daily oscillations in expression are maintained in constant darkness. While CRY1 has been well established as a TIM homolog in mammals, the role of CRY1 as a photoreceptor in mammals has been controversial. Early papers indicated that CRY1 has both light-independent and -dependent functions. A study conducted by Selby CP et al. (2000) found that mice without rhodopsin but with cryptochrome still respond to light; however, in mice without either rhodopsin or cryptochrome, c-Fos transcription,

4268-533: The (6-4) photolyase proteins than to plant cryptochrome proteins. It is therefore likely that plant and animal cryptochrome proteins show a unique case of convergent evolution by repeatedly evolving new functions independently of each other from a single common ancestral cry gene. Research by Worthington et al. (2003) indicates that cryptochromes first evolved in bacteria and were identified in Vibrio cholerae . Genome sequencing of this bacteria identified three genes in

4365-538: The 1880s, it was not until the 1980s that research began to identify the pigment responsible. In 1980, researchers discovered that the HY4 gene of the plant Arabidopsis thaliana was necessary for the plant's blue light sensitivity, and, when the gene was sequenced in 1993, it showed high sequence homology with photolyase , a DNA repair protein activated by blue light. Reference sequence analysis of cryptochrome-1 isoform d shows two conserved domains with photolyase proteins. Isoform d nucleotide positions 6 through 491 show

4462-465: The 3rd millennium BC, or possibly earlier. The earliest written evidence is a Linear B clay tablet found in Messenia that dates to between 1450 and 1350 BC, making Greek the world's oldest recorded living language . Among the Indo-European languages, its date of earliest written attestation is matched only by the now-extinct Anatolian languages . The Greek language is conventionally divided into

4559-513: The C-terminal end, due to the changes in genome and appearance that result from the lack of DNA repair enzymes . The Ramachandran plot shows that the secondary structure of the CRY1 protein is primarily a right-handed alpha helix with little to no steric overlap. The structure of CRY1 is almost entirely made up of alpha helices, with several loops and few beta sheets . In plants, cryptochromes mediate phototropism , or directional growth toward

4656-579: The C-terminus and the given phosphorylated segment could then liberate the transcription factor HY5 by competing for the same binding site at the negative regulator of photomorphogenesis COP1 . A different mechanism may function in Drosophila . The true ground state of the flavin cofactor in Drosophila CRY is still debated, with some models indicating that the FAD is in an oxidized form, while others support

4753-470: The CRY pathway, in which it is believed that the rhodopsin pathway is providing some light input. Recently, it has also been shown that there is a CRY-mediated light response that is independent of the classical circadian CRY-TIM interaction. This mechanism is believed to require a flavin redox -based mechanism that is dependent on potassium channel conductance. This CRY-mediated light response has been shown to increase action potential firing within seconds of

4850-486: The Greek alphabet since approximately the 9th century BC. It was created by modifying the Phoenician alphabet , with the innovation of adopting certain letters to represent the vowels. The variant of the alphabet in use today is essentially the late Ionic variant, introduced for writing classical Attic in 403 BC. In classical Greek, as in classical Latin, only upper-case letters existed. The lower-case Greek letters were developed much later by medieval scribes to permit

4947-425: The Greek language are often emphasized. Although Greek has undergone morphological and phonological changes comparable to those seen in other languages, never since classical antiquity has its cultural, literary, and orthographic tradition been interrupted to the extent that one can speak of a new language emerging. Greek speakers today still tend to regard literary works of ancient Greek as part of their own rather than

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5044-491: The Greek language was the Cypriot syllabary (also a descendant of Linear A via the intermediate Cypro-Minoan syllabary ), which is closely related to Linear B but uses somewhat different syllabic conventions to represent phoneme sequences. The Cypriot syllabary is attested in Cyprus from the 11th century BC until its gradual abandonment in the late Classical period, in favor of the standard Greek alphabet. Greek has been written in

5141-629: The Greek verb have likewise remained largely the same over the course of the language's history but with significant changes in the number of distinctions within each category and their morphological expression. Greek verbs have synthetic inflectional forms for: Many aspects of the syntax of Greek have remained constant: verbs agree with their subject only, the use of the surviving cases is largely intact (nominative for subjects and predicates, accusative for objects of most verbs and many prepositions, genitive for possessors), articles precede nouns, adpositions are largely prepositional, relative clauses follow

5238-661: The Greek-Albanian border. A significant percentage of Albania's population has knowledge of the Greek language due in part to the Albanian wave of immigration to Greece in the 1980s and '90s and the Greek community in the country. Prior to the Greco-Turkish War and the resulting population exchange in 1923 a very large population of Greek-speakers also existed in Turkey , though very few remain today. A small Greek-speaking community

5335-550: The PMTR of the chicken iris striated muscle occurs with CRY gene activation by 430 nm blue light. The PMTR was inhibited in CRY gene knockouts and decreased when flavin reductase was inhibited, but remained intact with the addition of melanopsin antagonists. Similarly, cytosolic CRY1 and CRY2 proteins were found in iris myotubes , and decreasing transcription of these genes inhibited PMTRs. The greatest iris PMTRs therefore correspond with

5432-404: The acute during the late 20th century, and it has only been retained in typography . After the writing reform of 1982, most diacritics are no longer used. Since then, Greek has been written mostly in the simplified monotonic orthography (or monotonic system), which employs only the acute accent and the diaeresis. The traditional system, now called the polytonic orthography (or polytonic system),

5529-402: The ancient language; singular and plural alone in later stages), and gender (masculine, feminine, and neuter), and decline for case (from six cases in the earliest forms attested to four in the modern language). Nouns, articles, and adjectives show all the distinctions except for a person. Both attributive and predicative adjectives agree with the noun. The inflectional categories of

5626-493: The arrhythmicity of these protein levels, cry mutants still showed rhythmicity in overall behavior but could not entrain to short pulses of light, leading researchers to conclude that the dorsal and ventral lateral neurons (the primary pacemaker cells of Drosophila) were still functioning effectively. When cry mutants also had visually unresponsive compound eyes, though, they failed to behaviorally entrain to environmental cues . These findings led researchers to conclude that

5723-471: The binding of CRY to other clock gene products, PER and TIM , in a light-dependent manner. Once bound by dCRY, dTIM is committed to degradation by the ubiquitin- proteasome system. Although light pulses do not entrain, full photoperiod LD cycles can still drive cycling in the ventral - lateral neurons in the Drosophila brain. These data along with other results suggest that CRY is the cell-autonomous photoreceptor for body clocks in Drosophila and may play

5820-400: The biosynthesis of purines and one pyrimidine . Substituted pteridines are intermediates in the biosynthesis of dihydrofolic acid in many microorganisms. The enzyme dihydropteroate synthetase converts pteridine and 4-aminobenzoic acid to dihydrofolic acid in the presence of glutamate . The enzyme dihydropteroate synthetase is inhibited by sulfonamide antibiotics . Molybdopterin

5917-428: The characteristics of an N-terminal photolyase homology (PHR) domain. The PHR domain can bind to the flavin adenine dinucleotide (FAD) cofactor and a light-harvesting chromophore . The structure of cryptochrome involves a fold very similar to that of photolyase, arranged as an orthogonal bundle with a single molecule of FAD noncovalently bound to the protein. These proteins have variable lengths and surfaces on

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6014-471: The circadian clock, while in mammals, cryptochromes (CRY1 and CRY2) act as transcription repressors within the circadian clockwork. Some insects, including the monarch butterfly , have both a mammal-like and a Drosophila -like version of cryptochrome, providing evidence for an ancestral clock mechanism involving both light-sensing and transcriptional-repression roles for cryptochrome. Cry mutants have altered circadian rhythms, showing that Cry affects

6111-550: The circadian pacemaker. Drosophila with mutated Cry exhibit little to no mRNA cycling. A point mutation in cry, which is required for flavin association in CRY protein, results in no PER or TIM protein cycling in either DD or LD. In addition, mice lacking Cry1 or Cry2 genes exhibit differentially altered free running periods, but are still capable of photoentrainment . However, mice that lack both Cry1 and Cry2 are arrhythmic in both LD and DD and always have high Per1 mRNA levels. These results suggest that cryptochromes play

6208-455: The cryptochrome protein encoded by cry is necessary for Drosophila photoentrainment. In mammals, a protein analog of the Drosophila cryptochrome protein was discovered with the characteristic property of lacking photolyase activity, prompting researchers to consider it in the same class of cryptochrome proteins. In mice, the greatest cry1 expression is observed in the suprachiasmatic nucleus (SCN) where levels rhythmically fluctuate. Due to

6305-439: The development of striated, rather than smooth, muscle fibers through CRY -mediated PMTRs. Studies in animals and plants suggest that cryptochromes play a pivotal role in the generation and maintenance of circadian rhythms. Similarly, cryptochromes play an important role in the entrainment of circadian rhythms in plants. In Drosophila , cryptochrome (dCRY) acts as a blue-light photoreceptor that directly modulates light input into

6402-404: The early 19th century that was used for literary and official purposes in the newly formed Greek state. In 1976, Dimotiki was declared the official language of Greece, after having incorporated features of Katharevousa and thus giving birth to Standard Modern Greek , used today for all official purposes and in education . The historical unity and continuing identity between the various stages of

6499-602: The epics of Homer , ancient Greek literature includes many works of lasting importance in the European canon . Greek is also the language in which many of the foundational texts in science and philosophy were originally composed. The New Testament of the Christian Bible was also originally written in Greek. Together with the Latin texts and traditions of the Roman world , the Greek texts and Greek societies of antiquity constitute

6596-404: The eyes of most animals use photo-sensitive opsins expressed in photoreceptor cells, which communicate information about light from the environment to the nervous system. However, A. queenslandica lacks a nervous system, like other sponges . And it does not have an opsin gene in its fully sequenced genome either, despite having many other G-protein-coupled receptors (GPCRs). Therefore,

6693-452: The following periods: In the modern era, the Greek language entered a state of diglossia : the coexistence of vernacular and archaizing written forms of the language. What came to be known as the Greek language question was a polarization between two competing varieties of Modern Greek: Dimotiki , the vernacular form of Modern Greek proper, and Katharevousa , meaning 'purified', a compromise between Dimotiki and Ancient Greek developed in

6790-478: The gene. It causes a delay by increasing the affinity of CLOCK and BMAL which in turn lengthens the period. This causes people with this mutation to have a later sleep midpoint than the rest of the population, causing a disorder known as delayed sleep–wake phase disorder . CRY1 is also a key modulator in DNA repair , specifically through temporal regulation. CRY1 has an impact in the cell cycle progression, particularly in

6887-439: The infinitive entirely (employing a raft of new periphrastic constructions instead) and uses participles more restrictively. The loss of the dative led to a rise of prepositional indirect objects (and the use of the genitive to directly mark these as well). Ancient Greek tended to be verb-final, but neutral word order in the modern language is VSO or SVO. Modern Greek inherits most of its vocabulary from Ancient Greek, which in turn

6984-463: The late 15th century BC, was the first script used to write Greek. It is basically a syllabary , which was finally deciphered by Michael Ventris and John Chadwick in the 1950s (its precursor, Linear A , has not been deciphered and most likely encodes a non-Greek language). The language of the Linear B texts, Mycenaean Greek , is the earliest known form of Greek. Another similar system used to write

7081-424: The lifetime of the activated form of cryptochrome. Activation of cryptochrome may affect the light-sensitivity of retinal neurons, with the overall result that the animal can sense the magnetic field. Animal cryptochromes and closely related animal (6-4) photolyases contain a longer chain of electron-transferring tryptophans than other proteins of the cryptochrome-photolyase superfamily (a tryptophan tetrad instead of

7178-621: The membership of Greece and Cyprus in the European Union, Greek is one of the organization's 24 official languages . Greek is recognized as a minority language in Albania, and used co-officially in some of its municipalities, in the districts of Gjirokastër and Sarandë . It is also an official minority language in the regions of Apulia and Calabria in Italy. In the framework of the European Charter for Regional or Minority Languages , Greek

7275-533: The methyl group at position 6 of the pteridine ring system (known as pteroic acid) conjugated with one or more L - glutamates . They participate in numerous biological group transfer reactions. Folate-dependent biosynthetic reactions include the transfer of methyl groups from 5-methyltetrahydrofolate to homocysteine to form L -methionine , and the transfer of formyl groups from 10-formyltetrahydrofolate to L -methionine to form N -formylmethionine in initiator tRNAs . Folates are also essential for

7372-441: The modern period. The division into conventional periods is, as with all such periodizations, relatively arbitrary, especially because, in all periods, Ancient Greek has enjoyed high prestige, and the literate borrowed heavily from it. Across its history, the syllabic structure of Greek has varied little: Greek shows a mixed syllable structure, permitting complex syllabic onsets but very restricted codas. It has only oral vowels and

7469-399: The noun they modify and relative pronouns are clause-initial. However, the morphological changes also have their counterparts in the syntax, and there are also significant differences between the syntax of the ancient and that of the modern form of the language . Ancient Greek made great use of participial constructions and of constructions involving the infinitive, and the modern variety lacks

7566-521: The objects of study of the discipline of Classics . During antiquity , Greek was by far the most widely spoken lingua franca in the Mediterranean world . It eventually became the official language of the Byzantine Empire and developed into Medieval Greek . In its modern form , Greek is the official language of Greece and Cyprus and one of the 24 official languages of the European Union . It

7663-706: The older periods of Greek, loanwords into Greek acquired Greek inflections, thus leaving only a foreign root word. Modern borrowings (from the 20th century on), especially from French and English, are typically not inflected; other modern borrowings are derived from Albanian , South Slavic ( Macedonian / Bulgarian ) and Eastern Romance languages ( Aromanian and Megleno-Romanian ). Greek words have been widely borrowed into other languages, including English. Example words include: mathematics , physics , astronomy , democracy , philosophy , athletics , theatre, rhetoric , baptism , evangelist , etc. Moreover, Greek words and word elements continue to be productive as

7760-480: The only proteins known to form photoinduced radical-pairs in vivo . These appear to enable some animals to detect magnetic fields. Cryptochromes have been the focus of several current efforts in optogenetics . Employing transfection , initial studies on yeast have capitalized on the potential of CRY2 heterodimerization to control cellular processes, including gene expression , by light. Although Charles Darwin first documented plant responses to blue light in

7857-461: The photolyase/cryptochrome family, all of which have the folate and flavin cofactors characteristic of these proteins. Of these genes, one encodes a photolyase, while the other two encode cryptochrome proteins designated VcCry1 and VcCry2. Cashmore AR et al. (1999) hypothesize that mammalian cryptochromes developed later in evolutionary history shortly after plants and animals diverged based on conserved genomic domains between animal cryptochromes and

7954-545: The pigments of butterfly wings (hence the origin of their name, from the Greek pteron ( πτερόν ), wing) and perform many roles in coloration in the biological world. Pterins exhibit a wide range of tautomerism in water, beyond what is assumed by just keto-enol tautomerism . For the unsubstituted pterin, at least five tautomers are commonly cited. For 6-methylpterin, seven tautomers are theoretically predicted to be important in solution. The pteridine ring system contains four nitrogen atoms, reducing its aromaticity to

8051-695: The point that it can be attacked by nucleophile . Pterins can take three oxidation states on the ring system: the unprefixed oxidized form, the 7,8-dihydro semi-reduced form (among other, less stable tautomers), and finally the 5,6,7,8-tetrahydro fully-reduced form. The latter two are more common in biological systems. Pterin rings are either salvaged from existing ones or produced de novo in living organisms. The ring comes from rearrangement of guanosine in bacteria and humans. Pterin derivatives are common cofactors in all domains of life. One important family of pterin derivatives are folates . Folates are pterins that contain p -aminobenzoic acid connected to

8148-508: The repair of UV-induced DNA damage . In eukaryotes , cryptochromes no longer retain this original enzymatic activity. By using a T-DNA labeled allele of the cry1 gene in the Arabidopsis plant, researchers determined that the cry1 gene encoded a flavoprotein without photolyase activity and with a unique C-terminal tail . The protein encoded by this gene was named cryptochrome 1 to distinguish it from its ancestral photolyase proteins and

8245-576: The role of the SCN as the primary mammalian pacemaker as well as the rhythmic fluctuations in cry1 expression, researchers concluded cry1 was also necessary for the entrainment of mammalian circadian rhythms. A common misconception in the evolutionary history of cryptochrome proteins is that mammalian and plant proteins are orthologs of each other that evolved directly from a shared photolyase gene. However, genomic analysis indicates that mammalian and fly cryptochrome proteins show greater sequence similarity to

8342-483: The sponge's unique eyes must have evolved a different mechanism to detect light and mediate phototaxis, possibly with cryptochromes or other proteins. Isolated irises constrict in response to light via a photomechanical transduction response (PMTR) in a variety of species and require either melanopsin or cryptochrome to do so. The iris of chicken embryos senses short-wavelength light via a cryptochrome, rather than opsins. Research by Margiotta and Howard (2020) shows that

8439-437: The stressed vowel; the so-called breathing marks ( rough and smooth breathing ), originally used to signal presence or absence of word-initial /h/; and the diaeresis , used to mark the full syllabic value of a vowel that would otherwise be read as part of a diphthong. These marks were introduced during the course of the Hellenistic period. Actual usage of the grave in handwriting saw a rapid decline in favor of uniform usage of

8536-594: The switch from the vegetative to the flowering stage of development. In Arabidopsis , CRY1 is the primary inhibitor of hypocotyl elongation but CRY2 inhibits hypocotyl elongation under low blue light intensity. CRY2 promotes flowering under long-day conditions. CRY gene mediates photomorphogenesis in several ways. CRY C-terminal interacts with CONTITUTIVE PHOTOMORPHOGENIC 1 (COP1), a E3 ubiquitin ligase that represses photomorphogenesis and flowering time. The interaction inhibits COP1 activity and allows transcription factors such as ELONGATED HYPOCOTYL 5 (HY5) to accumulate. HY5

8633-421: The synthesis of neurotransmitters catecholamine and serotonin. Tetrahydrobiopterin is also required for the functioning of alkylglycerol monooxygenase, whereby monoalkylglycerols are broken down to glycerol and an aldehyde. In the synthesis of nitric oxide the pterin-dependent nitric oxide synthase converts arginine to its N -hydroxy derivative, which in turn releases nitric oxide. Tetrahydromethanopterin

8730-453: The topic, cryptochrome photoreception and phototransduction in Drosophila and Arabidopsis thaliana is still poorly understood. Cryptochromes are known to possess two chromophores: pterin (in the form of 5,10-methenyltetrahydrofolic acid (MTHF)) and flavin (in the form of FAD). Both may absorb a photon , and in Arabidopsis , pterin appears to absorb at a wavelength of 380 nm and flavin at 450 nm. Past studies have supported

8827-587: The transduction of a light signal into a chemical signal in plant cryptochromes, which could be triggered by a photo-induced negative charge on the FAD cofactor or on the neighboring aspartic acid within the protein. This negative charge would electrostatically repel the protein-bound ATP molecule and thereby also the protein C-terminal domain, which covers the ATP binding pocket prior to photon absorption. The resulting change in protein conformation could lead to phosphorylation of previously inaccessible phosphorylation sites on

8924-568: Was a distinct dialect of Greek itself. Aside from the Macedonian question, current consensus regards Phrygian as the closest relative of Greek, since they share a number of phonological, morphological and lexical isoglosses , with some being exclusive between them. Scholars have proposed a Graeco-Phrygian subgroup out of which Greek and Phrygian originated. Among living languages, some Indo-Europeanists suggest that Greek may be most closely related to Armenian (see Graeco-Armenian ) or

9021-549: Was also used as the official language of government and religion in the Christian Nubian kingdoms , for most of their history. Greek, in its modern form, is the official language of Greece, where it is spoken by almost the entire population. It is also the official language of Cyprus (nominally alongside Turkish ) and the British Overseas Territory of Akrotiri and Dhekelia (alongside English ). Because of

9118-546: Was also used in Ancient Greek. Greek has occasionally been written in the Latin script , especially in areas under Venetian rule or by Greek Catholics . The term Frankolevantinika / Φραγκολεβαντίνικα applies when the Latin script is used to write Greek in the cultural ambit of Catholicism (because Frankos / Φράγκος is an older Greek term for West-European dating to when most of (Roman Catholic Christian) West Europe

9215-497: Was found to be involved in the photoreception of blue light. Studies of Drosophila cry- knockout mutants led to the later discovery that cryptochrome proteins are also involved in regulating the mammalian circadian clock. The Drosophila cry gene similarly encodes a flavoprotein without photolyase activity that also binds pterin chromophores . Cry mutants ( cry) were found to express arrhythmic levels of luciferase as well as PER and TIM proteins in photoreceptor cells. Despite

9312-566: Was under the control of the Frankish Empire ). Frankochiotika / Φραγκοχιώτικα (meaning 'Catholic Chiot') alludes to the significant presence of Catholic missionaries based on the island of Chios . Additionally, the term Greeklish is often used when the Greek language is written in a Latin script in online communications. The Latin script is nowadays used by the Greek-speaking communities of Southern Italy . The Yevanic dialect

9409-653: Was written by Romaniote and Constantinopolitan Karaite Jews using the Hebrew Alphabet . In a tradition, that in modern time, has come to be known as Greek Aljamiado , some Greek Muslims from Crete wrote their Cretan Greek in the Arabic alphabet . The same happened among Epirote Muslims in Ioannina . This also happened among Arabic-speaking Byzantine rite Christians in the Levant ( Lebanon , Palestine, and Syria ). This usage

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