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41-556: HBII-52 belongs to the C/D box class of snoRNAs which contain the conserved sequence motifs known as the C box (UGAUGA) and the D box (CUGA). Most of the members of the box C/D family function in directing site-specific 2'-O- methylation of substrate RNAs. In the human genome, HBII-52 is encoded in a tandemly repeated array with another C/D box snoRNA, HBII-85 (SNORD116) , in the Prader-Willi syndrome (PWS) region of chromosome 15 . However,

82-438: A bioinformatic approach. Of these, a large fraction were found to be alternatively spliced, suggesting a role of SNORD116 in the regulation of alternative splicing. More recently, SNORD90 has been suggested to be able to guide N6-methyladenosine (m6A) modifications onto target RNA transcripts. More specifically, Lin et al. demonstrated that SNORD90 can reduce the expression of neuregulin 3 (NRG3). The precise effect of

123-623: A microdeletion in one family of the snoRNA HBII-52 cluster has excluded it from playing a major role in the disease. HBII-52 is found in 47 tandem near identical copies on human chromosome 15q11-13. This locus is maternally imprinted, meaning that only the paternal copy of the locus is transcribed. HBII-52 is exclusively expressed in the brain but is absent in PWS patients. HBII-52 lacks any significant complementarity with ribosomal RNAs , but does have an 18 nucleotide region of conserved complementarity to serotonin 2C receptor mRNA. The serotonin 2C receptor

164-489: A series of processing steps to generate the mature rRNA molecule. Prior to cleavage by exo- and endonucleases, the pre-rRNA undergoes a complex pattern of nucleoside modifications. These include methylations and pseudouridylations, guided by snoRNAs. Each snoRNA molecule acts as a guide for only one (or two) individual modifications in a target RNA. In order to carry out modification, each snoRNA associates with at least four core proteins in an RNA/protein complex referred to as

205-399: A small nucleolar ribonucleoprotein particle (snoRNP). The proteins associated with each RNA depend on the type of snoRNA molecule (see snoRNA guide families below). The snoRNA molecule contains an antisense element (a stretch of 10–20 nucleotides ), which are base complementary to the sequence surrounding the base ( nucleotide ) targeted for modification in the pre-RNA molecule. This enables

246-451: A unique alphanumerical ID that will not change. Most subject headings come with a short description or definition. See the MeSH description for diabetes type 2 as an example. The explanatory text is written by the MeSH team based on their standard sources if not otherwise stated. References are mostly encyclopaedias and standard textbooks of the subject areas. References for specific statements in

287-490: Is L7Ae)—which make up the core C/D box snoRNP. There exists a eukaryotic C/D box snoRNA ( snoRNA U3 ) that has not been shown to guide 2′- O -methylation. Instead, it functions in rRNA processing by directing pre-rRNA cleavage. H/ACA box snoRNAs have a common secondary structure consisting of a two hairpins and two single-stranded regions termed a hairpin-hinge-hairpin-tail structure. H/ACA snoRNAs also contain conserved sequence motifs known as H box (consensus ANANNA) and

328-454: Is a member of the H/ACA-like class of non-coding RNA ( ncRNA ) molecule (a snoRNA) that guide the sites of modification of uridines to pseudouridines of substrate RNAs. TB11Cs4H1 is predicted to guide the pseudouridylation of LSU3 ribosomal RNA ( rRNA ) at residue Ψ1357. Medical Subject Headings Medical Subject Headings ( MeSH ) is a comprehensive controlled vocabulary for

369-504: Is also expressed in the brain. It has been shown that this snoRNA is likely to bind to a silencing element of exon Vb increasing its inclusion and production of a functional spliceform of the serotonin 2C receptor. The chromosomal locus containing the SNORD115 gene cluster has been duplicated in many individuals with autistic traits . A mouse model engineered to have a duplication of the SNORD115 cluster displays autistic-like behaviour. There

410-504: Is divided into four types of terms. The main ones are the "headings" (also known as MeSH headings or descriptors ), which describe the subject of each article (e.g., "Body Weight", "Brain Edema" or "Critical Care Nursing"). Most of these are accompanied by a short description or definition, links to related descriptors, and a list of synonyms or very similar terms (known as entry terms ). MeSH contains approximately 30,000 entries (as of 2022 ) and

451-452: Is done by the snoRNA HBII-52 , which is also known as SNORD115. In November 2012, Schubert et al. revealed that specific RNAs control chromatin compaction and accessibility in Drosophila cells. In July 2023, Lin et al. showed that snoRNAs have the potential to guide other RNA modifications, specifically N6-methyladenosine , however this is subject to further investigation. TB11Cs4H1

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492-476: Is evidence that a truncated form of MBII-52 (SNORD115 found in mouse) regulates the alternative splicing of the protein coding genes DPM2 , TAF1 , RALGPS1 , PBRM1 , and CRHR1 . SnoRNA#C.2FD box In molecular biology , small nucleolar RNAs ( snoRNAs ) are a class of small RNA molecules that primarily guide chemical modifications of other RNAs, mainly ribosomal RNAs , transfer RNAs and small nuclear RNAs . There are two main classes of snoRNA,

533-473: Is evidence that some of these orphan snoRNAs regulate alternatively spliced transcripts. For example, it appears that the C/D box snoRNA SNORD115 regulates the alternative splicing of the serotonin 2C receptor mRNA via a conserved region of complementarity. Another C/D box snoRNA, SNORD116 , that resides in the same cluster as SNORD115 has been predicted to have 23 possible targets within protein coding genes using

574-622: Is likely the catalytic component of the ribonucleoprotein (RNP) complex because it possesses several conserved pseudouridine synthase sequences, and is closely related to the pseudouridine synthase that modifies uridine in tRNA . In lower eukaryotic cells such as trypanosomes, similar RNAs exist in the form of single hairpin structure and an AGA box instead of ACA box at the 3′ end of the RNA. Like Trypanosomes, Entamoeba histolytica has mix population of single hairpin as well as double hairpin H/ACA box snoRNAs. It

615-437: Is updated annually to reflect changes in medicine and medical terminology. MeSH terms are arranged in alphabetic order and in a hierarchical structure by subject categories with more specific terms arranged beneath broader terms. When we search for a MeSH term, the most specific MeSH terms are automatically included in the search. This is known as the extended search or explode of that MeSH term. This additional information and

656-423: The 29 copies of SNORD116 (HBII-85) from this region has been identified as a cause of Prader-Willi syndrome whereas gain of additional copies of SNORD115 has been linked to autism . Region 14q32 contains repeats of two snoRNAs SNORD113 (9 copies) and SNORD114 (31 copies) within the introns of a tissue-specific ncRNA transcript ( MEG8 ). The 14q32 domain has been shown to share common genomic features with

697-496: The ACA box (ACA). Both motifs are usually located in the single-stranded regions of the secondary structure. The H motif is located in the hinge and the ACA motif is located in the tail region; 3 nucleotides from the 3′ end of the sequence. The hairpin regions contain internal bulges known as recognition loops in which the antisense guide sequences (bases complementary to the target sequence) are located. These guide sequences essentially mark

738-599: The C and D motifs (referred to as C' and D') located in the central portion of the snoRNA molecule. A conserved region of 10–21 nucleotides upstream of the D box is complementary to the methylation site of the target RNA and enables the snoRNA to form an RNA duplex with the RNA. The nucleotide to be modified in the target RNA is usually located at the 5th position upstream from the D box (or D' box). C/D box snoRNAs associate with four evolutionary conserved and essential proteins— fibrillarin (Nop1p), NOP56 , NOP58 , and SNU13 (15.5-kD protein in eukaryotes; its archaeal homolog

779-417: The C/D box snoRNAs, which are associated with methylation , and the H/ACA box snoRNAs, which are associated with pseudouridylation . SnoRNAs are commonly referred to as guide RNAs but should not be confused with the guide RNAs that direct RNA editing in trypanosomes or the guide RNAs (gRNAs) used by Cas9 for CRISPR gene editing . After transcription , nascent rRNA molecules (termed pre-rRNA) undergo

820-505: The article's major topics. When performing a MEDLINE search via PubMed, entry terms are automatically translated into (i.e., mapped to) the corresponding descriptors with a good degree of reliability; it is recommended to check the 'Details tab' in PubMed to see how a search formulation was translated. By default, a search for a descriptor will include all the descriptors in the hierarchy below the given one. PubMed does not apply automatic mapping of

861-665: The descriptions are not given; instead, readers are referred to the bibliography. In addition to the descriptor hierarchy, MeSH contains a small number of standard qualifiers (also known as subheadings ), which can be added to descriptors to narrow down the topic. For example, "Measles" is a descriptor and "epidemiology" is a qualifier; "Measles/epidemiology" describes the subheading of epidemiological articles about Measles. The "epidemiology" qualifier can be added to all other disease descriptors. Not all descriptor/qualifier combinations are allowed since some of them may be meaningless. In all there are 83 different qualifiers. In addition to

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902-404: The descriptor "Digestive System Neoplasms" has the tree numbers C06.301 and C04.588.274; C stands for Diseases, C06 for Digestive System Diseases and C06.301 for Digestive System Neoplasms; C04 for Neoplasms, C04.588 for Neoplasms By Site, and C04.588.274 also for Digestive System Neoplasms. The tree numbers of a given descriptor are subject to change as MeSH is updated. Every descriptor also carries

943-526: The descriptors, MeSH also contains some 318,000 supplementary concept records . These do not belong to the controlled vocabulary as such; instead they enlarge the thesaurus and contain links to the closest fitting descriptor to be used in a MEDLINE search. Many of these records describe chemical substances. In MEDLINE/PubMed, every journal article is indexed with about 10–15 subject headings, subheadings and supplementary concept records, with some of them designated as major and marked with an asterisk, indicating

984-630: The field, has approved unique names for human genes that encode snoRNAs. C/D box snoRNAs contain two short conserved sequence motifs, C (RUGAUGA) and D (CUGA), located near the 5′ and 3′ ends of the snoRNA, respectively. Short regions (~ 5 nucleotides) located upstream of the C box and downstream of the D box are usually base complementary and form a stem-box structure, which brings the C and D box motifs into close proximity. This stem-box structure has been shown to be essential for correct snoRNA synthesis and nucleolar localization. Many C/D box snoRNA also contain an additional less-well-conserved copy of

1025-471: The hierarchical structure (see below) make the MeSH essentially a thesaurus , rather than a plain subject headings list. The second type of term, MeSH subheadings or qualifiers (see below), can be used with MeSH terms to more completely describe a particular aspect of a subject, such as adverse, diagnostic or genetic effects. For example, the drug therapy of asthma is displayed as asthma/drug therapy. The remaining two types of term are those that describe

1066-519: The human genome, there are at least two examples where C/D box snoRNAs are found in tandem repeats within imprinted loci. These two loci (14q32 on chromosome 14 and 15q11q13 on chromosome 15) have been extensively characterised, and in both regions multiple snoRNAs have been found located within introns in clusters of closely related copies. In 15q11q13, five different snoRNAs have been identified ( SNORD64 , SNORD107, SNORD108, SNORD109 (two copies), SNORD116 (29 copies) and SNORD115 (48 copies). Loss of

1107-494: The imprinted 15q11-q13 loci and a possible role for tandem repeats of C/D box snoRNAs in the evolution or mechanism of imprinted loci has been suggested. snoRNAs can function as miRNAs . It has been shown that human ACA45 is a bona fide snoRNA that can be processed into a 21- nucleotides -long mature miRNA by the RNAse III family endoribonuclease dicer . This snoRNA product has previously been identified as mmu-miR-1839 and

1148-421: The location of the uridine on the target rRNA that is going to be modified. This recognition sequence is bipartite (constructed from the two different arms of the loop region) and forms complex pseudo-knots with the target RNA. H/ACA box snoRNAs associate with four evolutionary conserved and essential proteins— dyskerin (Cbf5p), GAR1 , NHP2 , and NOP10 —which make up the core of the H/ACA box snoRNP. Dyskerin

1189-476: The methylation and pseudouridylation modifications on the function of the mature RNAs is not yet known. The modifications do not appear to be essential but are known to subtly enhance the RNA folding and interaction with ribosomal proteins. In support of their importance, target site modifications are exclusively located within conserved and functionally important domains of the mature RNA and are commonly conserved among distant eukaryotes. A novel method, Nm-REP-seq,

1230-655: The modification of RNA polymerase II transcribed spliceosomal RNAs U1, U2, U4, U5 and U12. Not all snoRNAs that have been localised to Cajal bodies are composite C/D and H/ACA box snoRNAs. The targets for newly identified snoRNAs are predicted on the basis of sequence complementarity between putative target RNAs and the antisense elements or recognition loops in the snoRNA sequence. However, there are increasing numbers of 'orphan' guides without any known RNA targets, which suggests that there might be more proteins or transcripts involved in rRNA than previously and/or that some snoRNAs have different functions not concerning rRNA. There

1271-525: The presence of conserved sequence motifs in the snoRNA. There are exceptions, but as a general rule C/D box members guide methylation and H/ACA members guide pseudouridylation. The members of each family may vary in biogenesis, structure, and function, but each family is classified by the following generalised characteristics. For more detail, see review. SnoRNAs are classified under small nuclear RNA in MeSH . The HGNC , in collaboration with snoRNABase and experts in

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1312-466: The protein component of the H/ACA snoRNP result in a reduction in physiological TERC levels. This has been strongly correlated with the pathology behind DKC, which seems to be primarily a disease of poor telomere maintenance. An unusual guide snoRNA U85 that functions in both 2′-O-ribose methylation and pseudouridylation of small nuclear RNA (snRNA) U5 has been identified. This composite snoRNA contains both C/D and H/ACA box domains and associates with

1353-521: The proteins specific to each class of snoRNA (fibrillarin and Gar1p, respectively). More composite snoRNAs have now been characterised. These composite snoRNAs have been found to accumulate in a subnuclear organelle called the Cajal body and are referred to as small Cajal body-specific RNAs (scaRNAs). This is in contrast to the majority of C/D box or H/ACA box snoRNAs, which localise to the nucleolus. These Cajal body specific RNAs are proposed to be involved in

1394-616: The purpose of indexing journal articles and books in the life sciences . It serves as a thesaurus that facilitates searching. Created and updated by the United States National Library of Medicine (NLM), it is used by the MEDLINE / PubMed article database and by NLM's catalog of book holdings. MeSH is also used by ClinicalTrials.gov registry to classify which diseases are studied by trials registered in ClinicalTrials. MeSH

1435-447: The snoRNP to recognise and bind to the target RNA. Once the snoRNP has bound to the target site, the associated proteins are in the correct physical location to catalyse the chemical modification of the target base. The two different types of rRNA modification (methylation and pseudouridylation) are directed by two different families of snoRNAs. These families of snoRNAs are referred to as antisense C/D box and H/ACA box snoRNAs based on

1476-409: The term in the following circumstances: by writing the quoted phrase (e.g. "kidney allograft"), when truncated on the asterisk (e.g. kidney allograft * ), and when looking with field labels (e.g. Cancer [ti] ). At ClinicalTrials.gov , each trial has keywords that describe the trial. The ClinicalTrials.gov team assigns each trial two sets of MeSH terms. One set is for the conditions studied by

1517-540: The type of material that the article represents ( publication types ), and supplementary concept records (SCR) which describes substances such as chemical products and drugs that are not included in the headings (see below as " Supplements "). The descriptors or subject headings are arranged in a hierarchy. A given descriptor may appear at several locations in the hierarchical tree. The tree locations carry systematic labels known as tree numbers , and consequently one descriptor can carry several tree numbers. For example,

1558-647: Was developed for enriching 2'-O-Methylations guided by C/D snoRNAs by using RNA exoribonuclease (Mycoplasma genitalium RNase R, MgR) and periodate oxidation reactivity to eliminate 2'-hydroxylated (2'-OH) nucleosides. SnoRNAs are located diversely in the genome. The majority of vertebrate snoRNA genes are encoded in the introns of genes encoding proteins involved in ribosome synthesis or translation, and are synthesized by RNA polymerase II . SnoRNAs are also shown to be located in intergenic regions, ORFs of protein coding genes, and UTRs. SnoRNAs can also be transcribed from their own promoters by RNA polymerase II or III . In

1599-648: Was introduced in the 1960s, with the NLM's own index catalogue and the subject headings of the Quarterly Cumulative Index Medicus (1940 edition) as precursors. The yearly printed version of MeSH was discontinued in 2007; MeSH is now available only online. It can be browsed and downloaded free of charge through PubMed. Originally in English, MeSH has been translated into numerous other languages and allows retrieval of documents from different origins. MeSH vocabulary

1640-494: Was reported that there occurred processing of the double hairpin H/ACA box snoRNA to the single hairpin snoRNAs however, unlike trypanosomes, it has a regular ACA motif at 3′ tail. The RNA component of human telomerase (hTERC) contains an H/ACA domain for pre-RNP formation and nucleolar localization of the telomerase RNP itself. The H/ACA snoRNP has been implicated in the rare genetic disease dyskeratosis congenita (DKC) due to its affiliation with human telomerase. Mutations in

1681-410: Was shown to be processed independently from the other miRNA-generating endoribonuclease drosha . Bioinformatical analyses have revealed that putatively snoRNA-derived, miRNA-like fragments occur in different organisms. Recently, it has been found that snoRNAs can have functions not related to rRNA. One such function is the regulation of alternative splicing of the trans gene transcript, which

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