Species-specific elements in the large T-antigen J domain are required forcellular transformation and DNA replication by simian virus 40

The J domain of simian virus 40 (SV40) large T antigen is required for effi cient DNA replication and transformation. Despite previous reports demonstr ating the promiscuity of J domains in heterologous systems, results present ed here show the requirement for specific J-domain sequences in SV40 large- T-antigen-mediated activities. In particular, chimeric-T-antigen constructs in which the SV40 T-antigen J domain was replaced with that from the yeast Ydj1p or Escherichia coil DnaJ proteins failed to replicate in BSC40 cells and did not transform REF52 cells. However, T antigen containing the JC vi rus J domain was functional in these assays, although it was less efficient than the wild type. The inability of some large-T-antigen chimeras to prom ote DNA replication and elicit cellular transformation was not due to a fai lure to interact with hsc70, since a nonfunctional chimera, containing the DnaJ J domain, bound hsc70. However, this nonfunctional chimeric T antigen was reduced in its ability to stimulate hsc70 ATPase activity and unable to liberate E2F from p130, indicating that transcriptional activation of fact ors required for cell growth and DNA replication may be compromised. Our da ta suggest that the T-antigen J domain harbors species-specific elements re quired for viral activities in vivo.