Involvement of simian virus 40 (SV40) small t antigen in trans activation of SV40 early and late promoters.
We have previously found that simian virus 40 (SV40) small t antigen (small t) can trans activate the E2A and VA-I genes of adenovirus in plasmid DNA-transfected cells (M. R. Loeken, I. Bikel, D. M. Livingston, and J. Brady, Cell 55:1171-1177, 1988). To determine whether trans activation by small t might be involved in the SV40 productive infection cycle, we examined the effects of cotransfecting plasmids encoding small t with plasmids containing the chloramphenicol acetyltransferase (CAT) gene linked to the SV40 early or late promoter. Small t increased three- to fivefold the expression of a CAT plasmid linked to the SV40 early promoter and enhancer. Small t expression had no effect by itself on CAT activity directed by the SV40 late promoter, but small t enhanced the effect of a suboptimal concentration of a plasmid expressing large T up to 10-fold. When the concentration of the plasmid expressing large T was increased to a level at which large T alone stimulated the late promoter ninefold, the enhancement by small t was only twofold. The effects of small t on both the SV40 early and late promoters depended on sequences within the small t-unique domain, since a plasmid expressing only the first 82 amino acids common to both large T and small t was inactive. The effects of small t on early- and late-promoter-directed CAT enzyme activity was reflected in increased CAT mRNA as measured by S1 analysis. These results suggest that SV40 small t may play a role in viral infection by increasing transcription from the early promoter and from the late promoter at times when large T levels are low.
Bikel
I
I
Dana-Farber Cancer Institute, Boston, Massachusetts 02115.
Loeken
M R
MR
D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000502:physiology*; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D015967:Gene Expression Regulation, Viral; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D013539:Simian virus 40 / Q000235:genetics*; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D000952:Antigens, Polyomavirus Transforming; D012333:RNA, Messenger