Phenotypic Characterization of Adenovirus Type 12 Temperature‐Sensitive Mutants in Productive Infection and Transformation

Abstract

Eleven temperature-sensitive mutants of adenovirus type 12, capable of forming plaques in human cells at 33 C but not at 39.5 C, were isolated from a stock of a wild-type strain after treatment with either nitrous acid or hydroxylamine. Complementation tests in doubly infected human cells permitted a tentative assignment of eight of these mutants to six complementation groups. Temperatureshift experiments revealed that one mutant is affected early and most of the other mutants are affected late. Only the early mutant, H12ts505, was temperature sensitive in viral DNA replication. Infectious virions of all the mutants except H12ts505 and two of the late mutants produced at 33 C, appeared to be more heat labile than those of the wild type.Only H12ts505 was temperature sensitive for the establishment of transformation of rat 3Y1 cells. One of the late mutants (H12ts504) had an increased transforming ability at the permissive temperature.Results of temperature-shift transformation experiments suggest that a viral function affected in H12ts505 is required for "initiation" of transformation. Some of the growth properties of H12ts505-transformed cells were also temperature dependent, suggesting that a functional expression of a gene mutated in Hl2ts505 is required to maintain at least some aspects of the transformed state.Adenovirus type 12 (Ad12) causes two types of infection in cell culture, productive infection of human cells that leads to the production of progeny virions and eventual cell death, and abortive infection of hamster and rat cells that leads to transformation of a fraction of the infected cells (13). The viral mutants which are defective in productive infection at a high temperature are useful tools for examining the viral functions required for replication of this virus. Such temperature-sensitive (ts) mutants may also be useful for analyzing the viral gene function(s), if any, required for the establishment and maintenance of cell transformation by this highly oncogenic adenovirus. Isolation and characterization of ts mutants of Ad12 have been reported from several laboratories