|Alt. Symbols||Y1; Y2; Y3; Y5|
Y RNAs are small non-coding RNAs. They are components of the Ro60 ribonucleoprotein particle which is a target of autoimmune antibodies in patients with systemic lupus erythematosus. They are also necessary for DNA replication through interactions with chromatin and initiation proteins.
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.
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, 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.
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. 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. In Deinococcus, free Ro has also been shown to function in 23S rRNA maturation. In Deinococcus, mutants lacking Y RNA are viable, and Y RNA appears to be unstable except when complexed with Ro.
DNA replication initiation
Human Y RNAs are functionally required for DNA replication. 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 and specific degradation of human Y RNAs inhibits DNA replication in vitro, and in intact cells in vivo. Y RNA function is thought to be mediated via interactions with chromatin and initiation proteins (including the origin recognition complex)
In human pathology
Y RNAs are overexpressed in some human tumours and required for cell proliferation and small, microRNA-sized breakdown products may be involved in autoimmunity and other pathological conditions.
Presumptive Y RNA and Ro protein homologs have been found in eukaryotes and bacteria. Humans appear to have four Y RNAs, named hY1, hY3, hY4 and hY5 and also a large number of pseudogenes. C. elegans has one, named CeY RNA and a large number of sbRNAs that are postulated to also be Y RNA homologues. 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. 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.
- Y RNAs: recent developments. Adam E. Hall, Carly Turnbull, Tamas Dalmay. Biomolecular Concepts. 2013 January; 4(2):103-110. doi:10.1515/bmc-2012-0050.
- Lerner, MR; Boyle JA; Hardin JA; Steitz JA (1981). "Two novel classes of small ribonucleoproteins detected by antibodies associated with lupus erythematosus". Science. 211 (4480): 400–402. doi:10.1126/science.6164096. PMID 6164096.
- Christov CP, Gardiner TJ, Szüts D, Krude T (2006). "Functional Requirement of Noncoding Y RNAs for Human Chromosomal DNA Replication". Mol. Cell. Biol. 26 (18): 6993–7004. doi:10.1128/MCB.01060-06. PMC . PMID 16943439.
- Zhang, AT; Langley, AR; Christov, CP; Kheir, E; Shafee, T; Gardiner, TJ; Krude, T (Jun 15, 2011). "Dynamic interaction of Y RNAs with chromatin and initiation proteins during human DNA replication.". Journal of Cell Science. 124 (Pt 12): 2058–69. doi:10.1242/jcs.086561. PMC . PMID 21610089.
- Stein, AJ; Fuchs G; Fu C; Wolin SL; Reinisch KM (2005). "Structural insights into RNA quality control: The Ro autoantigen binds misfolded RNAs via its central cavity". Cell. 121 (4): 529–537. doi:10.1016/j.cell.2005.03.009. PMC . PMID 15907467.
- Teunissen SW, Kruithof MJ, Farris AD, Harley JB, Venrooij WJ, Pruijn GJ (2000). "Conserved features of Y RNAs: a comparison of experimentally derived secondary structures". Nucleic Acids Res. 28 (2): 610–9. doi:10.1093/nar/28.2.610. PMC . PMID 10606662.
- Green, CD; Long KS; Shi H; Wolin SL (1998). "Binding of the 60-kDa Ro autoantigen to Y RNAs: evidence for recognition in the major groove of a conserved helix". RNA. 4 (7): 750–765. doi:10.1017/S1355838298971667. PMC . PMID 9671049.
- Biogenesis of Y RNA-derived small RNAs is independent of the microRNA pathway. Francisco Esteban Nicolas, Adam E. Hall, Tibor Csorba, Carly Turnbull, Tamas Dalmay. FEBS Letters. 2012 April; 586(8):1226-1230. doi:10.1016/j.febslet.2012.03.026.
- Reinisch, KM; Wolin SL (2007). "Emerging themes in non-coding RNA quality control". Current Opinion in Structural Biology. 17 (2): 209–214. doi:10.1016/j.sbi.2007.03.012. PMID 17395456.
- Chen X, Wurtmann EJ, Van Batavia J, Zybailov B, Washburn MP, Wolin SL (2007). "An ortholog of the Ro autoantigen functions in 23S rRNA maturation in D. radiodurans". Genes Dev. 21 (11): 1328–39. doi:10.1101/gad.1548207. PMC . PMID 17510283.
- Christov CP, Trivier E, Krude T (March 2008). "Noncoding human Y RNAs are overexpressed in tumours and required for cell proliferation". Br. J. Cancer. 98 (5): 981–8. doi:10.1038/sj.bjc.6604254. PMC . PMID 18283318.
- Are the Ro RNP-associated Y RNAs concealing microRNAs? Y RNA-derived miRNAs may be involved in autoimmunity. Verhagen AP, Pruijn GJ. Bioessays. 2011 Sep;33(9):674-82. doi:10.1002/bies.201100048.
- Perreault J, Perreault JP, Boire G (2007). "Ro-associated Y RNAs in metazoans: evolution and diversification". Mol. Biol. Evol. 24 (8): 1678–89. doi:10.1093/molbev/msm084. PMID 17470436.
- Van Horn, DJ; Eisenberg D; O'Brien CA; Wolin SL (1995). "Caenorhabditis elegans embryos contain only one major species of Ro RNP". RNA. 1 (3): 293–303. PMC . PMID 7489501.
- Boria I, Gruber AR, Tanzer A, et al. (March 2010). "Nematode sbRNAs: Homologs of Vertebrate Y RNAs". J Mol Evol. 70 (4): 346–58. doi:10.1007/s00239-010-9332-4. PMID 20349053.
- Chen, X; Quinn AM; Wolin SL (2000). "Ro ribonucleoproteins contribute to the resistance of Deinococcus radiodurans to ultraviolet irradiation". Genes Dev. 14 (7): 777–782. doi:10.1101/gad.14.7.777. PMC . PMID 10766734.
- Chen, X.; Taylor, D. W.; Fowler, C. C.; Galan, J. E.; Wang, H.W.; Wolin, S. L. (2013). "An RNA degradation machine sculpted by Ro autoantigen and noncoding RNA". Cell. 153 (1): 166–77. doi:10.1016/j.cell.2013.02.037. PMC . PMID 23540697.