Michael Mller1, Verena Jantsch2, Michael Jantsch2, Gnter Steiner1. Ro ribonucleoproteins (RNPs) are small cytoplasmic particles of unknown function that have been found in all eukaryotes except yeasts. The core structure of human Ro RNPs is composed of one molecule of Y RNA to which the 60 kD Ro protein (Ro60) and La protein are stably bound. Ro RNPs are predominant target structures in the autoimmune diseases Systemic Lupus Erythematosus and Sjgrens syndrome and autoantibodies to Ro60 and La, can be frequently found in the sera of patients suffering from these diseases. The Ro60 protein is highly conserved in higher eukaryotes and the phenotype of a disruption of the gene encoding the C. elegans Ro60 homologue (rop-1
) was characterized (Labb et al. Genetics 1999, PNAS 2000). A decrease in Y RNA levels and a higher frequency of misfolded ribosome-associated 5s rRNAs was observed in rop-1
mutant worms. Rop-1 mutants were also shown to be defective in the formation of dauer larvae. Recently the structure of Ro60 was established (Stein et al. Cell 2005) and it was shown that the Y RNA binding site of Ro60 overlaps with the binding site for misfolded RNAs. These results suggest a regulatory role the Y RNA for the binding of misfolded RNAs to Ro60.. In humans and most other vertebrates four different Y RNAs are expressed, while in the nematode C. elegans only one Y RNA species has been found. The C. elegans Y RNA is highly conserved in its structure and most closely related to human Y3 RNA. Yet it differs from other eukaryotic Y RNAs as it is missing a 3 extension to which La is binding (van Horn et al. RNA 1995). To learn more about the function of Y RNAs, we took advantage of the fact that the C. elegans genome contains only a single Y RNA gene (yrn-1
). We generated a knock-out line of the C. elegans Y RNA by the method of gene targeting by biolistic transformation. Yrn-1 is located within an intron of an uncharacterized, protein-coding gene. We modified a method for gene disruption (Berezikov et al. Nucleic Acids Res. 2004) in our approach, as we deleted yrn-1
in our knock-out construct rather than disrupting the locus, which could have resulted in a double knock-out.. Yrn-1 mutant worms do not display any obvious morphological phenotype. However, preliminary results indicate that Y RNA deficient worms show a delayed response to chemoattractants. Future experiments are planned to elucidate the role of the Y RNA in damage repair upon UV induced damage, in coping with various forms of stress and in the dauer formation pathway.