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Molecular and Cellular Biology, January 2000, p. 113-125, Vol. 20, No. 1
0270-7306/0/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Alleviation of Human Papillomavirus E2-Mediated Transcriptional Repression via Formation of a TATA Binding Protein (or TFIID)-TFIIB-RNA Polymerase II-TFIIF Preinitiation Complex

Samuel Y. Hou, Shwu-Yuan Wu, Tianyuan Zhou, Mary C. Thomas, and Cheng-Ming Chiang*

Department of Biochemistry, University of Illinois, Urbana, Illinois 61801

Received 22 July 1999/Returned for modification 5 October 1999/Accepted 7 October 1999

Transcription in human papillomaviruses (HPVs) is mainly regulated by cellular transcription factors and virus-encoded E2 proteins that act as sequence-specific DNA-binding proteins. Although the functions of E2 as a transcriptional activator and a repressor have been well documented, the role of cellular factors involved in E2-mediated regulation of the HPV promoters and the mechanism by which E2 modulates viral gene expression remain unclear. Using reconstituted cell-free transcription systems, we found that cellular enhancer-binding factors and general cofactors, such as TAFIIs, TFIIA, Mediator, and PC4, are not required for E2-mediated repression. Unlike other transcriptional repressors that function through recruitment of histone deacetylase or corepressor complexes, HPV E2 is able to directly target components of the general transcription machinery to exert its repressor activity on the natural HPV E6 promoter. Interestingly, preincubation of TATA binding protein (TBP) or TFIID with HPV template is not sufficient to overcome E2-mediated repression, which can be alleviated only via formation of a minimal TBP (or TFIID)-TFIIB-RNA polymerase II-TFIIF preinitiation complex. Our data therefore indicate that E2 does not simply work by displacing TBP or TFIID from binding to the adjacent TATA box. Instead, E2 appears to function as an active repressor that directly inhibits HPV transcription at steps after TATA recognition by TBP or TFIID.

* Corresponding author. Mailing address: Department of Biochemistry, 430 Roger Adams Laboratory, University of Illinois, 600 South Mathews Ave., Urbana, IL 61801. Phone: (217) 244-3085. Fax: (217) 244-5858. E-mail: c-chiang{at}uiuc.edu.

Molecular and Cellular Biology, January 2000, p. 113-125, Vol. 20, No. 1
0270-7306/0/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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