MUTATIONS IN THE HUMAN PAPILLOMAVIRUS TYPE-16 E2 PROTEIN IDENTIFY MULTIPLE REGIONS OF THE PROTEIN INVOLVED IN BINDING TO E1

Human papillomavirus type 16 (HPV-16) DNA replicates episomally and re quires two virally expressed proteins, E1 and E2. The E1 protein has b oth helicase and ATPase activities and is absolutely required for vira l DNA replication. The E2 protein is a potent transcriptional activato r and greatly increases viral DNA replication by colocalizing E1 to th e origin of replication. Recently, we characterized a region of the E2 protein essential for the binding to E1. In this study we have analys ed in further detail the nature of the association between El and E2. Using an extensive set of E2 mutant proteins we have identified two wi dely separate regions of the E2 protein which are essential for bindin g to E1. Interestingly, two E2 mutants which fail to bind El also fail to activate gene expression, indicating the existence of multifunctio nal domains on the E2 protein. In addition, cotransfection of E1 with E2 significantly increases E2 transcriptional activity on an heterolog ous promoter.