Host range temperature-conditional mutants in the adenovirus DNA binding protein are defective in the assembly of infectious virus.

R(ts107)202 is a host range temperature-conditional mutant of adenovirus type 5. This mutant is temperature sensitive for replication and plaquing in 293 cells but is temperature independent for growth and plaquing in HeLa cells (J. C. Nicolas, F. Suarez, A. J. Levine, and M. Girard (1981) Virology 108, 521-524). The mutant was isolated in HeLa cells as a temperature-independent revertant of the H5ts107 temperature-sensitive mutant that maps in the adenovirus DNA binding protein (DBP). The reasons for the temperature conditional phenotype of this mutant in 293 cells were investigated. The mutant synthesized an unstable DBP in both HeLa and 293 cells at 39 degrees. In 293 cells at 39 degrees, about two- to threefold less viral DNA was synthesized by r(ts107)202 as compared to Ad5wt. R(ts107)202 infected cells at 39 degrees produced normal (wild-type) amounts of all detectable late viral structural proteins. The mutant failed, however, to produce infectious virus or assemble virus particles in 293 cells at 39 degrees. The altered DBP may therefore play a role in the assembly of virus particles, either directly or indirectly via an altered DNA structure. The failure of r(ts107)202 to assemble virion particles in 293 cells at 39 degrees furthermore suggests that virus assembly is dependent upon cellular factors that differ in HeLa and 293 cell.