The early region 2A gene (E2A) of adenovirus types 2 and 5 encodes a 72-kDa DNA binding protein (DBP) which contains two physical domains comprising approximately the amino-terminal one-third and carboxyl-terminal two-thirds of the protein, respectively. Previous work has shown that some Ads mutants containing temperature-sensitive (ts) mutations in the carboxyl-terminal domain of DBP, such as Ad5ts125, show a 3- to 8-fold enhanced ability to transform rat cells. We have examined the transformation characteristics of a series of Ad5 E2A deletion mutants, Ad5dl801-5, which encode either no functional DBP or encode truncated, defective DBPs. The E2A deletion mutants transformed rat embryo cells at frequencies similar to wild-type (wt) Ad5. These results suggest that the high transformation phenotype of carboxyl-terminal E2A mutants like Ad5ts125 is not due to the simple inactivation of DBP function, but rather results from an activity possessed by an altered DBP. This hypothesis is supported by the fact that the transformation phenotype of Adsts125 and similar mutants is dominant over the wild-type phenotype. A number of additional Ad2 and Ad5 E2A mutants were examined with respect to their ability to transform primary rat embryo cells. It was found that a carboxyl-terminal E2A mutant, Ad2+ND1ts23, also showed the enhanced transformation phenotype. In contrast, several amino-terminal E2A host-range (hr) mutants, originally isolated on the basis of their ability to replicate in monkey cells, transformed rat embryo cells at a frequency similar to wild-type virus. Ad2ts400, and E2A mutant with alterations in both DBP domains, showed a wilde-type frequency of transformation, while two similar mutants, Ad5tst25X405 and Ad5tsl25X404, showed an enhanced frequency. Last, it was found that coinfection of primary rat embryo cells with the hr mutants plus Ad5ts125 or Ad2+ND1ts23 resulted in a wild-type frequency of transformation, demonstrating that the hr mutants are dominant to the ts mutants with regard to transformation phenotype. Thus, DBP can both positively and negatively affect viral transformation in this system.
|Original language||English (US)|
|Number of pages||11|
|State||Published - Feb 1987|
Bibliographical noteFunding Information:
We thank Merlyn Williams for excellent technical assistance. This study was supported by Public Health Service Grant Al 17315 from the National Institutes of Health to D.F.K., and Grant CA-21 375 from the National Cancer Institute to J.W. S.A.R. was supported by predoctoral Training Grant T32GM07464-08 from NIH.