We have cloned a RAD51/DMC1 homolog in Caenorhabditis elegans , we named
Ce-hcr-51 for h omolog of Saccharomyces c erevisiae R AD 51 . This locus, we mapped on chromosome IV on the left of the
mec-3 gene on fosmid H36F17, is transcribed into two alternative mRNAs potentially coding for proteins of 395 (Hcr51L) and 357 (Hcr51S) aminoacids in length (Rinaldo et al. 1998). Experiments of RNA interference show that the inactivation of the locus results in adult hermaphrodite sterility of the F1. The F2 embryos show gross abnormality, develop to different stages, but they do not hatch, suggesting a meiotic defect leading to aneuploidy. We are also analysing the gene expression pattern by injecting the promoter sequences upstream the GFP/LacZ coding sequences, and by RNA analysis. We are using a two hybrid system assay to study the ability of the putative products of
hrc-51 to form homodymers and heterodymers in vivo . We identified two regions of the Hrc51S protein involved in the homodymerization process, one at the aminoterminal corresponding at the homodymerization domain already mapped in the yeast Rad51 protein (Donovan et al. 1994), and another located in the carboxiterminal half of Hrc-51 that seems to play a role either in the self-association activity or in stabilizing the protein. We are also studying proteins interacting with
Ce-hcr-51 products. Donovan J. W., Milne G. T., and Weaver D. T. (1994) Genes Dev 8 : 2552-62. Rinaldo C., Ederle S., Rocco V., and Volpe A. L. (1998) Mol. Gen. Genet. 260 : 289-294.