MUBC9, A NOVEL ADENOVIRUS E1A-INTERACTING PROTEIN THAT COMPLEMENTS A YEAST-CELL CYCLE DEFECT

Adenovirus E1A encodes two nuclear phosphoproteins that can transform primary rodent fibroblasts in culture, Transformation by E1A is mediat ed at least in part through binding to several cellular proteins, incl uding the three members of the retinoblastoma family of growth inhibit ory proteins, We report here the cloning of a novel murine cDNA whose encoded protein interacts with both adenovirus type 5 and type 12 E1A proteins. The novel E1A-interacting protein shares significant sequenc e homology with ubiquitin-conjugating enzymes, a family of related pro teins that is involved in the proteasome-mediated proteolysis of short -lived proteins. Highest homology was seen with a Saccharomyces cerevi siae protein named UBC9. importantly, the murine E1A-interacting prote in complements a cell cycle defect of a S, cerevisiae mutant which har bors a temperature-sensitive mutation in UBC9, me therefore named this novel E1A-interacting protein mUBC9. We mapped the region of E1A that is required for mUBC9 binding and found that the transformation-relev ant conserved region 2 of E1A is required for interaction.