Nuclear factor I and epithelial cell-specific transcription of human papillomavirus type 16.
The transcription of human papillomavirus type 16 (HPV-16) is mediated by the viral enhancer. Epithelial cell-specific activation is achieved by the cooperative interaction of apparently ubiquitous transcriptional factors. One of them, nuclear factor I (NFI), binds seven sites within the HPV-16 enhancer. Point mutations on enhancer fragments, which retain epithelial cell specificity, verify the functional contribution of NFI. In band shift experiments, the epithelial cell-derived NFI proteins CTF-1, CTF-2, and CTF-3 form a characteristic pattern of heterodimeric complexes which are observed in all epithelial cells tested. Divergence from this pattern in fibroblasts, liver cells, and lymphoid cells correlates with the lack of HPV-16 enhancer activation. The HPV-16 enhancer can be activated by CTF-1 in SL-2 cells, which lack NFI-like proteins. However, exogenous CTF-1 fails to overcome the inactivity of the viral enhancer in fibroblasts. Western immunoblot and supershift analysis shows that exogenously introduced CTF-1 proteins form different heterodimer complexes with the given subset of endogenous NFI proteins in epithelial or fibroblast cells. Polymerase chain reaction analysis and cDNA library screens identified the endogenous fibroblast type NFI as NFI-X, an NFI family member originally cloned from hamster liver cells. The strict correlation between the activation or lack of activation of the HPV-16 enhancer and cell-specific subsets of NFI proteins argues for the pivotal role of NFI binding sites in the epithelial cell-specific function of the viral enhancer.
Papillomavirus Biology Laboratory, National University of Singapore, Kent Ridge.
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D
Apt
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T
Chong
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Liu
H U
HU
Bernard
D001483:Base Sequence; D022762:CCAAT-Enhancer-Binding Proteins; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D004247:DNA; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D004848:Epithelium / Q000378:metabolism; D015723:Gene Library; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D051839:NFI Transcription Factors; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D027383:Papillomaviridae / Q000235:genetics* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid; D012867:Skin / Q000378:metabolism; D013379:Substrate Specificity; D014157:Transcription Factors; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured; D051840:Y-Box-Binding Protein 1
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D051839:NFI Transcription Factors; C497647:NFIC protein, human; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D014157:Transcription Factors; D051840:Y-Box-Binding Protein 1; C070856:YBX1 protein, human; D004247:DNA; D015500:Chloramphenicol O-Acetyltransferase