The cellular protein PRA1 modulates the anti-apoptotic activity of Epstein-Barr virus BHRF1, a homologue of Bcl-2, through direct interaction

The Epstein-Barr virus-encoded early protein, BHRF1, is a structural and fu nctional homologue of the anti-apoptotic protein, Bcl-2. There is accumulat ing evidence that BHRF1 protects a variety of cell types from apoptosis ind uced by various external stimuli. To identify specific proteins from normal epithelial cells that interact with BHRF1 and that might promote or inhibi t its anti-apoptotic activity, we screened a yeast two-hybrid cDNA library derived from human normal foreskin keratinocytes and identified a cellular gene encoding human prenylated rab acceptor 1 (hPRA1). The interaction of h PRA1. with BHRF1 was confirmed using glutathione S-transferase pull-down as says, confocal laser scanning microscopy, and co-immunoprecipitation. Two r egions of PRA1, amino acids 30-53 and the carboxyl-terminal 21 residues, ar e important for BHRF1 interactions and two regions of BHRF1, amino acids 1- 18 and 89-142, including the Bcl-2 homology domains BH4 and BH1, respective ly, are crucial for PRA1 interactions. PRA1 expression interferes with the anti-apoptotic activity of BHRF1, although not of Bcl-2. These results indi cate that the PRA1 interacts selectively with BHRF1 to reduce its anti-apop totic activity and might play a role in the impeding completion of virus ma turation.