Y RNA | |
---|---|
Identifiers | |
Symbol | Y_RNA |
Alt. Symbols | Y1; Y3; Y4; Y5 |
Rfam | RF00019 |
Other data | |
RNA type | Gene |
Domain(s) | Eukaryota |
SO | SO:0000405 |
PDB structures | PDBe |
Y RNAs are small non-coding RNAs. They are components of the Ro60 ribonucleoprotein particle [1] which is a target of autoimmune antibodies in patients with systemic lupus erythematosus. [2] They are also reported to be necessary for DNA replication through interactions with chromatin and initiation proteins. [3] [4] However, mouse embryonic stem cells lacking Y RNAs are viable and have normal cell cycles. [5]
These small RNAs are predicted to fold into a conserved stem formed by the RNA's 3′ and 5′ ends and characterized by a single bulged cytosine, which are the known requirements for Ro binding. [6] [7] [8]
Two functions have been described for Y RNAs in the literature: As a repressor of Ro60, and as an initiation factor for DNA replication. Mutant human Y RNAs lacking the conserved binding site for Ro60 protein still support DNA replication, [3] indicating that binding to Ro protein and promoting DNA replication are two separable functions of Y RNAs. Although Y RNA-derived small RNAs are similar in size to microRNAs, it has been shown that these Y RNA fragments are not involved in the microRNA pathway. [9]
In its free state, Ro binds to a variety of misfolded RNAs including misfolded 5S rRNAs, and is thought to act as some sort of quality control mechanism. [10] Crystal structures of Ro complexed either with Y RNA or another RNA showed that Ro binds single-stranded 3′ ends of RNAs relatively nonspecifically, whereas Y RNA binds specifically at a second site that regulates access of other RNAs. [6] In Deinococcus , free Ro has also been shown to function in 23S rRNA maturation. [11] In Deinococcus, mutants lacking Y RNA are viable, and Y RNA appears to be unstable except when complexed with Ro. [11]
Human Y RNAs are functionally required for DNA replication. [3] Biochemical fractionation and reconstitution experiments have established a functional requirement of human Y RNAs for chromosomal DNA replication in isolated vertebrate cell nuclei in vitro [3] and specific degradation of human Y RNAs inhibits DNA replication in vitro, and in intact cells in vivo . [3] Y RNA function is thought to be mediated via interactions with chromatin and initiation proteins (including the origin recognition complex) [4]
Y RNAs are overexpressed in some human tumours and are required for cell proliferation [12] and small, microRNA-sized breakdown products may be involved in autoimmunity and other pathological conditions. [13] Recent work has demonstrated that Y RNAs are modified at their 3′ end by the non-canonical poly(A) polymerase PAPD5, and the short oligo(A) tail added by PAPD5 is a marker for 3′ end processing by the ribonuclease PARN/EXOSC10 or for degradation by the exonuclease DIS3L. [14] Since PARN deficiency causes a severe form of the bone marrow disease Dyskeratosis Congenita as well as pulmonary fibrosis, [15] [16] it is possible that defects in Y RNA processing contribute to the severe pathology observed in these patients.
Presumptive Y RNA and Ro protein homologs have been found in eukaryotes and bacteria. [7] [17]
Humans appear to have four Y RNAs, named hY1, hY3, hY4 and hY5 [17] and also a large number of pseudogenes.
Caenorhabditis elegans has one, named CeY RNA and a large number of sbRNAs that are postulated to also be Y RNA homologues. [18] [19]
The radiation-resistant bacterium Deinococcus radiodurans encodes a homolog of Ro called rsr ("Ro sixty related"), and at least four small RNAs accumulate in Deinococcus under conditions where rsr expression is induced (UV irradiation); one of these RNAs appears to be a Y RNA homolog. [20] In Deinococcus radiodurans Rsr is tethered via Y RNA to the exoribonuclease PNPase and channels single-stranded RNA into the PNPase cavity. Rsr and Y RNA enhance degradation of structured RNAs by PNPase. This role could be conserved, as Rsr and ncRNAs called YrlA and YrlB (Y RNA like) also associate with PNPase in an evolutionary distant bacterium Salmonella Typhimurium. [21]
Non-coding DNA (ncDNA) sequences are components of an organism's DNA that do not encode protein sequences. Some non-coding DNA is transcribed into functional non-coding RNA molecules. Other functional regions of the non-coding DNA fraction include regulatory sequences that control gene expression; scaffold attachment regions; origins of DNA replication; centromeres; and telomeres. Some non-coding regions appear to be mostly nonfunctional such as introns, pseudogenes, intergenic DNA, and fragments of transposons and viruses.
A non-coding RNA (ncRNA) is a functional RNA molecule that is not translated into a protein. The DNA sequence from which a functional non-coding RNA is transcribed is often called an RNA gene. Abundant and functionally important types of non-coding RNAs include transfer RNAs (tRNAs) and ribosomal RNAs (rRNAs), as well as small RNAs such as microRNAs, siRNAs, piRNAs, snoRNAs, snRNAs, exRNAs, scaRNAs and the long ncRNAs such as Xist and HOTAIR.
In biology, the word gene can have several different meanings. The Mendelian gene is a basic unit of heredity and the molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and noncoding genes.
Interleukin enhancer-binding factor 3 is a protein that in humans is encoded by the ILF3 gene.
The perinucleolar compartment (PNC) is a subnuclear body characterized by its location at the periphery of the nucleolus. The PNC participates in the patterned compartmentalization inside the nucleus to organize the specialized functions. It is almost exclusively found in oncogenic cells and enriched with RNA binding proteins as well as RNA polymerase III transcripts.
Sjögren syndrome type B antigen (SS-B) also known as Lupus La protein is a protein that in humans is encoded by the SSB gene.
Tripartite motif-containing protein 21, also known as E3 ubiquitin-protein ligase TRIM21, is a protein that in humans is encoded by the TRIM21 gene. Alternatively spliced transcript variants for this gene have been described but the full-length nature of only one has been determined. It is expressed in most human tissues.
Chromatin assembly factor 1 subunit B is a protein that in humans is encoded by the CHAF1B gene.
Interleukin enhancer-binding factor 2 is a protein that in humans is encoded by the ILF2 gene.
60 kDa SS-A/Ro ribonucleoprotein is a protein that in humans is encoded by the TROVE2 gene.
Exosome component 4, also known as EXOSC4, is a human gene, which is part of the exosome complex.
3'-5' exoribonuclease CSL4 homolog is an enzyme that in humans is encoded by the EXOSC1 gene.
REX2, RNA exonuclease 2 homolog , also known as REXO2, is an enzyme which in humans is encoded by the REXO2 gene.
Zinc finger protein 330 is a protein that in humans is encoded by the ZNF330 gene.
Long non-coding RNAs are a type of RNA, generally defined as transcripts more than 200 nucleotides that are not translated into protein. This arbitrary limit distinguishes long ncRNAs from small non-coding RNAs, such as microRNAs (miRNAs), small interfering RNAs (siRNAs), Piwi-interacting RNAs (piRNAs), small nucleolar RNAs (snoRNAs), and other short RNAs. Long intervening/intergenic noncoding RNAs (lincRNAs) are sequences of lncRNA which do not overlap protein-coding genes.
HOTAIR is a human gene located between HOXC11 and HOXC12 on chromosome 12. It is the first example of an RNA expressed on one chromosome that has been found to influence transcription of HOXD cluster posterior genes located on chromosome 2. The sequence and function of HOTAIR is different in human and mouse. Sequence analysis of HOTAIR revealed that it exists in mammals, has poorly conserved sequences and considerably conserved structures, and has evolved faster than nearby HoxC genes. A subsequent study identified HOTAIR has 32 nucleotide long conserved noncoding element (CNE) that has a paralogous copy in HOXD cluster region, suggesting that the HOTAIR conserved sequences predates whole genome duplication events at the root of vertebrate. While the conserved sequence paralogous with HOXD cluster is 32 nucleotide long, the HOTAIR sequence conserved from human to fish is about 200 nucleotide long and is marked by active enhancer features.
Deinococcus radiodurans is an extremophilic bacterium and one of the most radiation-resistant organisms known. It can survive cold, dehydration, vacuum, and acid, and therefore is known as a polyextremophile. It has been listed as the world's toughest known bacterium in The Guinness Book Of World Records.
sbRNA is a family of non-coding RNA first discovered in Caenorhabditis elegans. It was identified during a full transcriptome screen of the C. elegans cDNA library. Subsequent experimentation characterised sbRNA as having conserved 5' and 3' internal motifs which form a long paired stem which is interrupted with a bulge.
Deinococcus deserti is a Gram-negative, rod-shaped bacterium that belongs to the Deinococcaceae, a group of extremely radiotolerant bacteria. D. deserti and other Deinococcaceae exhibit an extraordinary ability to withstand ionizing radiation.
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