Effect of mutations in rev gene of SIVmac on virus replication.

The functional activity of SIVmac251 Rev was altered by introducing amino acid changes inside and chain termination mutations after the Rev response element-binding region (RBR) of the protein. The effects of specific mutations were evaluated by transfecting proviral DNAs into the HeLa cell line and into HeLa cells constitutively expressing either HIV-1 Rev or HTLV-1 Rex proteins. Cell-free supernatants from these transient expression assays were further characterized by infecting CD4-positive lymphoid cell lines H9 and MT-4, the latter abortively infected with HTLV-1, and human peripheral blood mononuclear cells. These results together with the data from cotransfection experiments show that SIV can be attenuated up to 95% by introducing changes into the arginine-rich domain, RBR, of Rev. These recessive mutations were efficiently complemented in trans by HIV-1 Rev, SIV Rev, and HTLV-I Rex proteins. In contrast, the mutants of Rev protein that had a chain termination after RBR were trans-dominant negative and could not be trans-complemented with any of these three regulatory proteins. When additional mutations were inserted into the RBR of these trans-dominantly negative Rev proteins, complementation was obtained again.