Abstract
The early gene of wild-type (wt) SV40 specifies two related proteins, referred to as large (Mr 88,000) and small (Mr 19,000) T-antigen. Infection with wt SV40 of Go/G1-arrested monkey kidney and CV-1 cell cultures induced in virtually 100% of the cells T-antigen synthesis, followed by a mitotic reaction and the production of SV40 DNA. Parallel cultures were infected with SV40 deletion mutants that produce either no small T-antigen (d1883) or only trace amounts of a truncated form (d1891). Kinetics of synthesis and accumulation of large T-antigen was closely similar to that observed with wtSV40 whereas apparently only 50-60% of the cells participated in the mitotic reaction and the production of viral DNA. These results and those obtained from a comparative study on the abortive (transforming) infection in Go-arrested mouse tissue culture cells indicate that synthesis of large T-antigen alone is sufficient to trigger in 50-60% of the infected cells a mitotic reaction.
Highlights
SV40 is a small oncogenic DNA virus wich induces tumors and leukemias in hamsters (1,2)
Infection with wt SV40 of Go/Gl-arrested monkey kidney and CV-1 cell cultures induced in virtually 100% of the cells T-antigen synthesis, followed by a mitotic reaction and the production of SV40 DNA
In monkey kidney cultures infected with wt SV40, dl883 or dl891, T-antigen could be detected by the immunofluorescence reaction in 1% of the nuclei by 8-9 hours, in 50-80% by 16 hours and in virtually 100% of the nuclei by 24 hours after infection
Summary
SV40 is a small oncogenic DNA virus wich induces tumors and leukemias in hamsters (1,2). The primary transcript of the early gene of wt SV40 undergoes two types of splicing: the removal of an intervening sequence (IVS), extending from 0.533-0.600 map units (346 bp) on the physical map of SV40 DNA, results in the mRNA coding large T-antigen (708 aa; Mr 88000), the major early viral protein; removal of an IVS extending from 0.533-0.546 map units (66 bp) leads to the mRNA which codes small T-antigen (174 aa; Mr 19000) (1,2,4). In lytic infection of monkey kidney or CV-1 cultures (a monkey kidney cell line) S-phase is paralleled by the replication of SV40 DNA, the production of progeny virus and is followed by cell lysis. In transforming (abortive) infection of primary mouse kidney cultures, which are nonpermissive for SV40, S-phase is followed by mitosis without viral DNA replication (1-3, 8,9)
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