Varley C L, Bacon E J, Holder J C, Southgate J
Jack Birch Unit of Molecular Carcinogenesis, Department of Biology, University of York, York YO10 5YW, UK.
Cell Death Differ. 2009 Jan;16(1):103-14. doi: 10.1038/cdd.2008.116. Epub 2008 Aug 8.
The peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-activated transcription factor that has been implicated in the induction of differentiation of various cell types, including human uroepithelial cells. PPARgamma-mediated differentiation of normal human urothelial (NHU) cells in vitro requires coinhibition of epidermal growth factor receptor (EGFR) signalling and is characterised by de novo expression of late/terminal differentiation-associated genes, including uroplakins (UPK), over a 6-day period. We used gene microarrays to identify intermediary transcription factors induced in direct response to PPARgamma activation of EGFR-inhibited NHU cells. FOXA1 and IRF-1 contained consensus cognate binding sites in UPK1a, UPK2, and UPK3a promoters and transcripts were induced within 12 h of PPARgamma activation; transcription complex formation was confirmed by electromobility shift assays. In urothelium in situ, both FOXA1 and IRF-1 were nuclear and expressed in a differentiation-associated pattern. Knockdown by transient siRNA of either FOXA1 or IRF-1 abrogated PPARgamma-induced uroplakin expression in vitro. This is the first evidence that ligand activation of PPARgamma induces expression of intermediary transcription factors that mediate an epithelial differentiation programme and represents a new paradigm for understanding differentiation, regenerative repair and inflammation in epithelial tissues.
过氧化物酶体增殖物激活受体γ（PPARγ）是一种配体激活的转录因子，与多种细胞类型（包括人尿道上皮细胞）的分化诱导有关。在体外，PPARγ介导的正常人尿道上皮（NHU）细胞分化需要同时抑制表皮生长因子受体（EGFR）信号传导，其特征是在6天时间内从头表达与晚期/终末分化相关的基因，包括uroplakins（UPK）。我们使用基因微阵列来鉴定在EGFR抑制的NHU细胞中因PPARγ激活而直接诱导产生的中间转录因子。FOXA1和IRF-1在UPK1a、UPK2和UPK3a启动子中含有共有同源结合位点，并且在PPARγ激活后12小时内转录本被诱导产生；通过电泳迁移率变动分析证实了转录复合物的形成。在原位尿道上皮中，FOXA1和IRF-1均位于细胞核内，并以与分化相关的模式表达。通过瞬时siRNA敲低FOXA1或IRF-1均可在体外消除PPARγ诱导的uroplakin表达。这是首个证据表明PPARγ的配体激活可诱导介导上皮分化程序的中间转录因子的表达，代表了理解上皮组织分化、再生修复和炎症的新范例。
