Function
Two functions have been described for Y RNAs in the literature: In one line of evidence, Y RNA appears to function as a repressor of Ro. 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. Secondly, it has been found that 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. Specific degradation of human Y RNAs in vitro, or in intact cells in vivo, have led to an inhibition of chromosomal DNA replication. Interestingly, 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. Another study, has shown that Y RNAs are overexpressed in human tumours and required for cell proliferation. Recent research supports the hypothesis that microRNA-sized, small RNAs generated from Y RNAs may be involved in autoimmunity and other pathological conditions. 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.
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