Transcription-positive cofactor 4 enhances rescue of adeno-associated virus genome from an infectious clone.

While Rep proteins are required for adeno-associated virus (AAV) replication, little is known about cellular proteins that interact with Rep. We demonstrate here that transcription-positive cofactor 4 (PC4, p15) fused to Gal4-activating domain interacted with both AAV-2 and AAV-3 Rep proteins fused to Gal4 DNA-binding domain, leading to reporter activation in the yeast two-hybrid system. In addition to its coactivating function, PC4 recently has been shown to be involved in replication of simian virus 40. To study a functional role for the PC4-Rep protein interaction, 293-31 cells were cotransfected with a PC4 expression plasmid and an infectious clone of AAV-3, followed by super-infection with helper adenovirus. A significantly increased number of AAV-3 genomes were rescued in PC4 transfected cells. Our results support a possible involvement of PC4 in AAV replication and may be used in efficient production of AAV vectors for gene therapy.