Binding of simian virus 40 large tumor antigen to phospholipid vesicles

SV40 T antigen is the initiator protein of SV40 DNA replication. We examined the interaction of purified SV40 T antigen with phospholipids by (i) centrifugation analysis with phospholipid vesicles, (ii) filter binding assay and footprint analysis of T antigen binding to the replication origin of SV40 DNA and (iii) analysis of the initiation of SV40 DNA replication in vitro. In all cases, cardiolipin showed affinity for T antigen and inhibited its DNA binding capacity. Phosphatidylglycerol with unsaturated fatty acids also inhibited the binding of T antigen to the replication origin of SV40 DNA, whereas phosphatidylglycerol with saturated fatty acids did not. This finding suggested the importance of unsaturated fatty acids for the interaction of T antigen with phospholipids. Other phospholipids including phosphatidylserine, phosphatidylinositol and phosphatidylethanolamine showed little or no affinity for T antigen.