MULTIPLE CELLULAR PROTEINS ARE RECOGNIZED BY THE ADENOASSOCIATED VIRUS REP78 MAJOR REGULATORY PROTEIN AND THE AMINO-HALF OF REP78 IS REQUIRED FOR MANY OF THESE INTERACTIONS

Adeno-associated virus (AAV) encoded Rep78 is a multi-functional prote in which is required for AAV DNA replication, is able to regulate both AAV and heterologous gene expression at the transcriptional level, an d appears necessary for site specific integration of AAV DNA into huma n chromosome 19. By comparison with the analogous replication protein of the polyomaviruses, large T antigen, it seemed likely that Rep78 wo uld interact with cellular proteins to carry out at least some its fun ctions. This study demonstrates that Rep78 is able to interact with mu ltiple cellular proteins from cellular extracts as measured by West(fa r)western, coimmunoprecipitation, and Rep78-affinity chromatography an alysis. Eight cellular proteins of approximately 180, 140, 120, 95, 75 , 55, 45, and 35 kDa (+/-10%), were observed to bind Rep78 in all thre e assay systems. Two others, of 30 and 24 kDa, were observed in two of three assay systems. Furthermore, using truncated Rep78 proteins, it is demonstrated that the amino-terminus is required for most Rep78-cel lular protein interactions. However, the extreme carboxy-terminus of R ep78 was found to be all that is required for binding to the 55 kDa ce llular protein.