title: Retinoic acid receptor α mediates all-trans-retinoic acid-induced Klf4 gene expression by regulating Klf4 promoter activity in vascular smooth muscle cells.
abstract: The transcription factor Krüppel-like factor 4 (KLF4) plays a critical role in vascular smooth muscle cell (VSMC) differentiation induced by all-trans-retinoic acid (ATRA). Although it has been demonstrated that ATRA stimulation augments both KLF4 protein and mRNA levels in VSMCs, the molecular mechanisms by which ATRA regulates Klf4 transcription are unknown. In this study, we examined the roles of ATRA-selective nuclear retinoic acid receptors (RARs) in the transcriptional regulation of Klf4. The introduction of small interfering RNA and an RAR antagonist demonstrated that RARα, but not RARβ or RARγ, mediated ATRA-induced Klf4 expression. A luciferase assay for the Klf4 promoter showed that three GC boxes in the proximal Klf4 promoter were indispensible for ATRA-induced Klf4 transcription and that RARα enhanced Klf4 promoter activity in a GC box-dependent manner. Furthermore, chromatin immunoprecipitation and oligonucleotide pulldown assays demonstrated that the transcription factors KLF4, Sp1, and YB1 directly bound to the GC boxes of the proximal Klf4 promoter. Upon RARα agonist stimulation, RARα was recruited to the Klf4 promoter through its interaction with KLF4, Sp1, and YB1 to form a transcriptional activation complex on the three GC boxes of the Klf4 promoter. These results suggest that RARα serves as an essential co-activator for ATRA signaling and that the recruitment of RARα to the KLF4-Sp1-YB1 complex, which leads to Klf4 expression in VSMCs, is independent of a retinoic acid response element.
authors.affiliation: Department of Biochemistry and Molecular Biology, the Key Laboratory of Neurobiology and Vascular Biology, China.
authors.forename: Jian-hong
authors.initials: JH
authors.lastname: Shi
authors.forename: Bin
authors.initials: B
authors.lastname: Zheng
authors.forename: Si
authors.initials: S
authors.lastname: Chen
authors.forename: Guo-yan
authors.initials: GY
authors.lastname: Ma
authors.forename: Jin-kun
authors.initials: JK
authors.lastname: Wen
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D055785:Gene Knockdown Techniques; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000172:deficiency / Q000235:genetics*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000187:drug effects*; D051381:Rats; D018168:Receptors, Retinoic Acid / Q000378:metabolism*; D020218:Response Elements / Q000187:drug effects; D000072482:Retinoic Acid Receptor alpha; D015398:Signal Transduction / Q000187:drug effects; D016329:Sp1 Transcription Factor / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects*; D014212:Tretinoin / Q000378:metabolism / Q000494:pharmacology*; D051840:Y-Box-Binding Protein 1 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism
chemical_list: C000715469:Klf4 protein, rat; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; C000607073:Rara protein, rat; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D016329:Sp1 Transcription Factor; D051840:Y-Box-Binding Protein 1; D014212:Tretinoin