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Journal of Virology, April 2005, p. 4246-4256, Vol. 79, No. 7
0022-538X/05/$08.00+0 doi:10.1128/JVI.79.7.4246-4256.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Queensland Institute of Medical Research and the University of Queensland, Brisbane, Queensland,1 Department of Infectious Diseases, University of Sydney, Sydney, New South Wales, Australia,3 Department of Physiology, University of Maryland School of Medicine, Rockville, Maryland2
Received 10 September 2004/ Accepted 26 October 2004
The serine protease inhibitor SerpinB2 (PAI-2), a major product of differentiating squamous epithelial cells, has recently been shown to bind and protect the retinoblastoma protein (Rb) from degradation. In human papillomavirus type 18 (HPV-18)-transformed epithelial cells the expression of the E6 and E7 oncoproteins is controlled by the HPV-18 upstream regulatory region (URR). Here we illustrate that PAI-2 expression in the HPV-18-transformed cervical carcinoma line HeLa resulted in the restoration of Rb expression, which led to the functional silencing of transcription from the HPV-18 URR. This caused loss of E7 protein expression and restoration of multiple E6- and E7-targeted host proteins, including p53, c-Myc, and c-Jun. Rb expression emerged as sufficient for the transcriptional repression of the URR, with repression mediated via the C/EBPß-YY1 binding site (URR 7709 to 7719). In contrast to HeLa cells, where the C/EBPß-YY1 dimer binds this site, in PAI-2- and/or Rb-expressing cells the site was occupied by the dominant-negative C/EBPß isoform liver-enriched transcriptional inhibitory protein (LIP). PAI-2 expression thus has a potent suppressive effect on HPV-18 oncogene transcription mediated by Rb and LIP, a finding with potential implications for prognosis and treatment of HPV-transformed lesions.
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