Effect of a tsA mutation of simian virus 40 late gene expression: variations between host cell lines.

Infection of AGMK or CV-1 cells by the early simian virus 40 mutant tsA58 at the permissive temperature (32 degrees C) followed by a shift to the nonpermissive temperature (41 degrees C) caused a substantial decrease in the levels of late viral RNA in the cytoplasm of AGMK cells but not CV-1 cells. At the translational level, this depression of late viral RNA levels was reflected by a decrease in late viral protein synthesis. Thus, in AGMK cells, an early region gene product (presumably large T-antigen) appeared to be continuously required for efficient expression of the late viral genes. In contrast, late simian virus 40 gene expression, once it is initiated in CV-1 cells, continued efficiently regardless of the tsA mutation. The difference in expression of the late simian virus 40 genes in these tsA mutant-infected monkey kidney cell lines may reflect a difference in host cell proteins which regulate viral gene expression in conjunction with early viral proteins.