title: Caenorhabditis elegans embryos contain only one major species of Ro RNP.
abstract: In virtually all vertebrate cells, Ro RNPs consist of the 60-kDa Ro autoantigen bound to one of several small cytoplasmic RNA molecules known as Y RNAs. Because the 60-kDa Ro autoantigen is also found complexed with defective precursors of 5S rRNA in Xenopus oocytes, we have proposed that this protein functions in a quality control, or discard pathway, for 5S RNA biosynthesis (O'Brien CA, Wolin SL, 1994, Genes & Dev 8:2891-2903). The role of the Y RNAs in this pathway is unknown. To begin a genetic analysis of Ro RNP function, we have characterized these particles in the nematode Caenorhabditis elegans. The C. elegans Ro protein is 12 kDa larger than the vertebrate protein; the larger size is due in part to an N-terminal extension and to two insertions in the RNA recognition motif. In contrast to all previously described vertebrate species, the Ro protein appears bound to a single Y RNA in C. elegans. Similar to vertebrate Y RNAs, the C. elegans Y RNA can be folded to form a pyrimidine-rich internal loop and a long stem in which the 5' and 3' ends are base paired. Within the stem is a conserved bulged helix that is proposed to be the binding site of the Ro protein. Interestingly, although the human protein can bind the nematode Y RNA, the C. elegans protein does not bind human Y RNAs. This is the first description of Ro RNPs in an invertebrate species.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001324:Autoantigens / Q000032:analysis* / Q000378:metabolism; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000737:chemistry* / Q000196:embryology; D006801:Humans; D015151:Immunoblotting; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011233:Precipitin Tests; D011485:Protein Binding; D012313:RNA / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins / Q000032:analysis* / Q000378:metabolism; D017423:Sequence Analysis, RNA; D017386:Sequence Homology, Amino Acid; D000099207:SS-A Antigen
chemical_list: D001324:Autoantigens; D012313:RNA; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins; D000099207:SS-A Antigen; C116006:RO60 protein, human