Methods for Studying Interactions Between Simian Virus 40 T-Antigen and the Viral Origin of Replication

The Simian virus 40 (SV40) DNA replication system has served as a useful model for studies of DNA synthesis in eukaryotes [for reviews, see (1 ,2 )]. One major advantage of this system is that, with the exception of one viral protein, termed T-antigen (T-ag), all of the proteins required for DNA replication are supplied by cells that are permissive for SV40 replication (3 ). Because the virus depends on host proteins for replication (4 ), the SV40 system has been used to identify many of the proteins required for DNA synthesis in eukaryotes [for reviews, see (5 -7 )]. Moreover, because T-ag binds to the SV40 origin of replication in a site-specific manner, this system has provided many insights into the protein-DNA interactions taking place at a eukaryotic origin during initiation of DNA replication [for reviews see (1 ,8 )]. Insights gained into the initiation on the SV40 origin are likely to be relevant to initiation events at other origins, because complicated biochemical processes are not believed to change radically once solved by evolution (9 ).