ACIDIC TRANSCRIPTION FACTORS ALLEVIATE NUCLEOSOME-MEDIATED REPRESSIONOF DNA-REPLICATION OF BOVINE PAPILLOMAVIRUS TYPE-1

The papillomavirus E2 transcription factor is directly involved in vir al DNA replication. Previous studies have shown that E2 interacts with both the viral E1 helicase and cellular replication proteins, and thu s it may facilitate their targeting to the origin of replication. We d emonstrate here that E1-mediated replication of bovine papillomavirus type 1 is repressed by nucleosomal assembly. The E2 protein counteract s this repression, and such activation requires the E2- binding sites adjacent to the origin of replication. These in vitro results are cons istent with the previous in vivo findings that both E2 and specific E2 binding to DNA are absolutely required for replication of bovine papi llomavirus, Furthermore, the function of E2 in preventing nucleosome-m ediated repression can be achieved as well by several other acidic tra nscription factors. These data therefore strongly support the idea tha t a group of enhancer proteins may utilize similar mechanisms to stimu late transcription and replication.