Characterization of mRAD18Sc, a mouse homolog of the yeast postreplicationrepair gene RAD18

The RAD18 gene of the yeast Saccharomyces cerevisiae encodes a protein with ssDNA binding activity that interacts with the ubiquitin-conjugating enzym e RAD6 and plays an important role in postreplication repair. We identified and characterized the putative mouse homolog of RAD18 designated mRAD18Sc. The mRAD18Sc open reading frame encodes a 509-amino-acid polypeptide that is strongly conserved in size and sequence between yeast and mammals, with specific conservation of the RING-zinc-finger and the classic zinc-finger d omain. The degree of sequence conservation between mRAD18Sc, RAD18, and hom ologous sequences identified in other species (NuvA from Aspergillus nidula ns and Uvs-2 from Neurospora crassa) is entirely consistent with the evolut ionary relationship of these organisms, strongly arguing that these genes a re one another's homologs, Consistent with the presence of a nuclear transl ocation signal in the amino acid sequence, we observed the nuclear localiza tion of GFP-tagged mRAD18Sc after stable transfection to HeLa cells. mRNA e xpression of mRAD18Sc in the mouse was observed in thymus, spleen, brain, a nd ovary, but was most pronounced in testis, with the highest level of expr ession in pachytene-stage primary spermatocytes, suggesting that mRAD18Sc p lays a role in meiosis of spermatogenesis. Finally, we mapped the nRAD18Sc gene on mouse chromosome 6F. (C) 2000 Academic Press.