TOSCA - A DROSOPHILA GENE ENCODING A NUCLEASE SPECIFICALLY EXPRESSED IN THE FEMALE GERMLINE

We describe here a Drosophila gene, tosca (tos), that is specifically expressed in the female germline. tos mRNA accumulates selectively wit hin the pro-oocyte in germarial region 2 and persists throughout oogen esis. In the early embryo, the maternally supplied tos mRNA is evenly distributed at the syncytial blastoderm stage, but is excluded from th e forming cells when cellularization begins. fos product is the first Drosophila member of the RAD2 protein family, a group of related DNA r epair nucleases conserved from yeast to humans, Within the family, Tos is more closely related to ExoI, a Schizosaccharomyces pombe 5' --> 3 ' double-stranded DNA exonuclease specifically induced in meiotic prop hase I. The definite oocyte localization of fos transcript during meio sis and its ubiquitous distribution in early embryos suggest that ros may play a role in mismatch repair during genetic recombination and ea rly cleavage divisions. (C) 1996 Academic Press, Inc.