Ro RNP associated Y RNAs are highly conserved among mammals

Y RNAs are small cytoplasmic RNAs which are components of the Ro ribonucleoprotein complexes in higher eukaryotes. These complexes are frequently recognized by antibodies present in autoimmune sera. In this study we analysed the occurrence of Y RNAs in various mammalian and human cell lines and erythrocytes by means of hybridization with human Y RNA probes. Y RNAs homologous to their human counterparts, both in length and in sequence, were detected in all mammalian cells analysed. While hY1 and hY3 analogues were found in all cells, Y4 and Y5 RNA could not be detected in rodent cells. In addition, Y5 RNA was absent from bovine cells. Attempts to determine the sequence of rat Y RNAs by genomic cloning resulted in the isolation of a presumptive Y1 RNA pseudogene. Analysis of the hY RNA content of various human cell lines showed that all four human Y RNAs were present in all cell lines examined. However, the relative levels to which these RNAs were expressed showed marked differences.