Interferon-alpha elicits downregulation of human papillomavirus 18 mRNA in HeLa cells by selective repression of endogenous viral transcription.
We have reported that interferon-alpha inhibits HPV-18 mRNA in HeLa cells. Here we examine mechanisms by which IFN could modulate HPV expression. In northern blot experiments, we observed that interferon-alpha 2b treatment reduced HPV-18 mRNA levels in a time- and dose-dependent manner, with a maximal effect achieved at 48 h. Simultaneously, induction of 2-5A synthetase mRNA was verified as indicative of IFN action. The IFN regulatory effect on HPV-18 mRNA at 48 h required de novo protein synthesis. We performed run-on experiments to determine whether the IFN regulatory effect was at the transcriptional level. HPV-18 endogenous transcription was repressed using 200 and 1000 IU/ml. Interferon treatment did not affect HPV-18 mRNA stability, at least under our experimental conditions. To verify whether HPV-18 enhancer sequences were involved in the interferon effect, we transfected a construct containing the chloramphenicol acetyltransferase driven by the HPV-18 upstream regulatory region. The enzyme activity was unmodified on human keratinocytes and HeLa cells by interferon exposition. Our data demonstrate that interferon-alpha downregulates HPV-18 mRNA levels on HeLa cells by repressing nascent viral transcripts, possibly through regulatory cellular flanking regions.
Perea
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SE
Departamento de Biología Celular, Centro de Investigaciones Biológicas, La Habana, Cuba.
López-Ocejo
O
O
García-Milian
R
R
Araña
M J
MJ
D015088:2',5'-Oligoadenylate Synthetase / Q000235:genetics; D015536:Down-Regulation / Q000187:drug effects; D004742:Enhancer Elements, Genetic; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D016898:Interferon-alpha / Q000494:pharmacology*; D027383:Papillomaviridae / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis*; D012367:RNA, Viral / Q000096:biosynthesis*; D012097:Repressor Proteins / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects*
D016898:Interferon-alpha; D012333:RNA, Messenger; D012367:RNA, Viral; D012097:Repressor Proteins; D015088:2',5'-Oligoadenylate Synthetase