ANALYSIS OF P107-ASSOCIATED PROTEINS - P107 ASSOCIATES WITH A FORM OFE2F THAT DIFFERS FROM PRB-ASSOCIATED E2F-1

The binding of viral oncogenes to cellular proteins is thought to modu late the activities of these cellular targets. The p107 protein is tar geted by many viral proteins, including adenovirus EIA, simian virus 4 0 large T antigen, and human papillomavirus type 16 E7 protein. A pane l of monoclonal antibodies against p107 was raised and used to identif y cellular proteins that interact with the p107 protein in vivo. p107- associated proteins included cyclin A, cyclin E, and cdk2. In addition , p107 was found to associate with 62- to 65- and 50-kDa phosphoprotei ns in ML-1 cells, a human myeloid leukemia cell line. The 62- to 65-kD a proteins have many of the properties of the transcription factor E2F but were distinguished from pRB-associated E2F-1 by both immunologic and biochemical properties.