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Journal of Virology, July 2005, p. 9254-9269, Vol. 79, No. 14
0022-538X/05/$08.00+0 doi:10.1128/JVI.79.14.9254-9269.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Department of Medical Biochemistry and Microbiology, Uppsala University, BMC, Box 582, 751 23 Uppsala, Sweden,1 Dublin Institute of Technology, Kevin Street, Dublin 8, Ireland2
Received 19 January 2005/ Accepted 15 March 2005
Production of human papillomavirus type 16 (HPV-16) virus particles is totally dependent on the differentiation-dependent induction of viral L1 and L2 late gene expression. The early polyadenylation signal in HPV-16 plays a major role in the switch from the early to the late, productive stage of the viral life cycle. Here, we show that the L2 coding region of HPV-16 contains RNA elements that are necessary for polyadenylation at the early polyadenylation signal. Consecutive mutations in six GGG motifs located 174 nucleotides downstream of the polyadenylation signal resulted in a gradual decrease in polyadenylation at the early polyadenylation signal. This caused read-through into the late region, followed by production of the late mRNAs encoding L1 and L2. Binding of hnRNP H to the various triple-G mutants correlated with functional activity of the HPV-16 early polyadenylation signal. In addition, the polyadenylation factor CStF-64 was also found to interact specifically with the region in L2 located 174 nucleotides downstream of the early polyadenylation signal. Staining of cervix epithelium with anti-hnRNP H-specific antiserum revealed high expression levels of hnRNP H in the lower layers of cervical epithelium and a loss of hnRNP H production in the superficial layers, supporting a model in which a differentiation-dependent down regulation of hnRNP H causes a decrease in HPV-16 early polyadenylation and an induction of late gene expression.
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