CELLULAR FACTORS REQUIRED FOR PAPILLOMAVIRUS DNA-REPLICATION

In vitro replication of papillomavirus DNA has been carried out,vith a combination of purified proteins and partially purified extracts made from human cells. DNA synthesis requires the viral Fl protein and the papillomavirus origin of replication. The E2 protein stimulates DNA s ynthesis in a binding site-independent manner. Papillomavirus DNA repl ication is also dependent on the cellular factors replication protein A, replication factor C, and proliferating-cell nuclear antigen as wel l as a phosphocellulose column fraction (IIA). Fraction IIA contains D NA polymerase alpha-primase and DNA polymerase delta. Both of these po lymerases are essential for papillomavirus DNA replication in vitro. H owever, unlike the case with T-antigen-dependent replication from the simian virus 40 origin, purified DNA polymerase alpha-primase and delt a cannot efficiently replace fraction IIA in the replication reaction. Hence, additional cellular factors seem to be required for papillomav irus DNA replication. Interestingly, replication factor C and prolifer ating-cell nuclear antigen are more stringently required for DNA synth esis in the papillomavirus system than in the simian virus 40 in vitro system. These distinctions indicate that there must be mechanistic di fferences between the DNA replication systems of papillomavirus and si mian virus 40.