A TEF-1-independent mechanism for activation of the simian virus 40 (SV40) late promoter by mutant SV40 large T antigens.
Simian virus 40 (SV40) large tumor antigen (T antigen) stimulates the activity of the SV40 late promoter and a number of cellular and other viral promoters. We have characterized the ability of T antigens with mutations in the DNA-binding domain and within the N-terminal 85 residues to activate the SV40 late promoter. T antigens lacking both nonspecific and sequence-specific DNA-binding activities were able to induce the late promoter. Mutations within the N-terminal 85 residues of T antigen diminished activation by less than twofold. Activation by wild-type and most of the mutant T antigens required intact binding sites for the cellular transcription factor TEF-1 in the late promoter. Curiously, two mutants altered in the N-terminal region and an additional mutant altered in the DNA-binding domain activated a late promoter derivative lacking TEF-1 binding sites, indicating the existence of a TEF-1-independent pathway for activation of the late promoter. A consensus binding site for the TATA binding protein, TBP, was created in variants of late promoters either containing or lacking TEF-1 binding sites. Basal expression was increased by the consensus TBP binding site only when TEF-1 binding sites were present, leading to a reduction in the degree of activation by T antigen. However, activation by a mutant T antigen of the promoter lacking TEF-1 sites was unchanged or slightly enhanced by the consensus TBP binding site. These results suggest that some mutant T antigens can stabilize an interaction between TBP and additional factors bound to the late promoter.
Casaz
P
P
Committee on Virology, Harvard Medical School, Boston, Massachusetts, USA.
Rice
P W
PW
Cole
C N
CN
Hansen
U
U
D000952:Antigens, Polyomavirus Transforming / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000502:physiology*; D009154:Mutation; D009687:Nuclear Proteins; D010641:Phenotype; D011401:Promoter Regions, Genetic; D013539:Simian virus 40 / Q000235:genetics*; D000091262:TEA Domain Transcription Factors; D014157:Transcription Factors / Q000502:physiology*
D000952:Antigens, Polyomavirus Transforming; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D000091262:TEA Domain Transcription Factors; C057182:TEAD1 protein, human; D014157:Transcription Factors