The adenovirus H5ts125 mutation is a temperature sensitive defect in the structural gene for a DNA-binding protein required for viral DNA replication. Infection of primary African green monkey kidney cells with SV40, followed by superinfection with H5ts125 at the nonpermissive temperature, permits the replication of adenovirus DNA even in the absence of detectable adenovirus DNA binding protein. The SV40 A gene product is required continuously for the replication of H5ts125 adenovirus DNA. The rate of adenovirus DNA replication in SV40 and H5ts125 doubly infected cells at nonpermissive temperature is about one-half that observed for either H5ts125 singly or SV40-H5ts125 doubly infected cells at the permissive temperature. H5ts125 progeny virus are also produced in the SV40-H5ts125-infected cells at the nonpermissive temperature but the yields are only 3% of those observed in doubly infected cells at the permissive temperature. The suppression of the H5ts125 phenotype by SV40 requires a prior infection of primary or secondary African green monkey kidney cells with a high multiplicity of SV40 (50-100 PFU/cell) and H5ts125 DNA replication is optimally observed between 10 and 15 hr after adenovirus superinfection. These observations suggest that the SV40 A gene product could be involved in the initiation of adenovirus DNA replication thereby bypassing the need for the adenovirus DNA-binding protein.
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