Transformation by adenovirus early region 2A temperature-sensitive mutants and their revertants

H5ts107 is a temperature-sensitive mutant of adenovirus type 5 whose alteration maps in the structural gene for the viral DNA binding protein. Temperature-independent revertants of this mutant that form plaques at 39° in HeLa cells have been isolated. These revertants fall into two classes: (1) ts⁺ revertants for growth and plaque formation at 39° in both HeLa cells and 293 cells, a human cell line transformed by type 5 adenovirus; (2) ts⁺ for growth and plaque formation at 39° in HeLa cells, but temperature-sensitive (ts) for growth and plaque formation in 293 cells. The frequency of rat cell transformation by H5tsl07 was fivefold higher than that of wild-type adenovirus. A class 1 revertant, r(tsl07)127, transformed cells at the wild-type virus frequency while a class 2 revertant, r(tsl07)202, retained the ability to transform cells at the higher frequency. When the XhoI-C DNA fragment from these viruses, which contains the left end 15.5% of the viral genome, was employed to transform rat cells, then Ad5 wt, H5tsl07, r(tsl07)127, and r(ts107)202 DNAs all transformed with approximately equal frequencies.