Identification and characterization of a Drosophila homologue of the yeastUBC9 and hus5 genes

The yeast UBC9 and hus5 gene products have been identified as putative E2 m embers of the ubiquitin-conjugating enzyme (UBC) family and have been shown to play an essential role in cell cycle progression. We have identified a Drosophila Ubc9/Hus5 homologue (termed dUBC9) in an attempt to identify pro teins that interact with the amino-terminal transcriptional repression doma in of the Groucho corepressor by use of the yeast two-hybrid system. The pr edicted dUBC9 protein consists of 159 amino acids and shows 85, 68, and 54% amino acid sequence identities with human UBC9 homologue, Schizosaccharomy ces pombe Hus5, and Saccharomyces cerevisiae Ubc9 proteins, respectively. E xpression of dUBC9 cDNA complements a temperature-sensitive ubc9-1 mutation of S, cerevisiae to fully restore normal growth, indicating that the dUBC9 protein can act as a substitute for the yeast Ubc9 protein. The dUBC9 tran scripts were about 1.2 kb and were detected at all stages of Drosophila dev elopment and in ovaries and Schneider cells, However, an increased level wa s observed in early embryos and ovaries. The dUBC9 gene is present as a sin gle copy in the genome and localized in segment 21C-D on the left arm of th e second chromosome.