DNA conformation driven by AP-1 triggers cell-specific expression via a strong epithelial enhancer.
We report here the characterization of the regulatory region of the human LAMA3 gene, coding for the alpha3A chain of laminin-5. A 202 bp fragment is sufficient to confer epithelial-specific expression to a thymidine kinase promoter through the cooperative effect of three AP-1 binding sites. Remarkably, removal of the sequences located between the AP-1 sites does not modify the promoter activity in keratinocytes but allows strong expression in fibroblasts. Replacement of the deleted sequences by non-homologous ones fully restores the restricted enhancement in keratinocytes. Functional analysis and mutagenesis experiments demonstrate that a minimal distance between the AP-1 sites is required for the enhancer DNA fragment to adopt a particular conformation driven by the binding of Jun-Fos heterodimers. In non-permissive cells, this conformation leads to the anchorage of non-DNA-binding fibroblastic cofactors to form an inhibitory ternary complex. Therefore, our results describe for the first time an unusual conformation-dependent epithelial-specific enhancer.
U385 INSERM, Faculté de Médecine, Nice, France.
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Virolle
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Djabari
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Ortonne
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Aberdam
D016475:3T3 Cells; D000818:Animals; D019556:COS Cells; D004847:Epithelial Cells / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism; D007797:Laminin / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D009690:Nucleic Acid Conformation; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D012045:Regulatory Sequences, Nucleic Acid; D013937:Thymidine Kinase / Q000235:genetics; D018808:Transcription Factor AP-1 / Q000235:genetics*; D015533:Transcriptional Activation; D014162:Transfection
D007797:Laminin; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; C095567:laminin alpha 3; D013937:Thymidine Kinase