FOXA1 and IRF-1 intermediary transcriptional regulators of PPARgamma-induced urothelial cytodifferentiation.
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.
Varley
C L
CL
Jack Birch Unit of Molecular Carcinogenesis, Department of Biology, University of York, York YO10 5YW, UK.
Bacon
E J
EJ
Holder
J C
JC
Southgate
J
J
D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D066246:ErbB Receptors / Q000378:metabolism; D020869:Gene Expression Profiling / Q000379:methods; D005786:Gene Expression Regulation / Q000502:physiology; D055785:Gene Knockdown Techniques; D051541:Hepatocyte Nuclear Factor 3-alpha / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D050856:Interferon Regulatory Factor-1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000096:biosynthesis; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D047495:PPAR gamma / Q000378:metabolism*; D034741:RNA, Small Interfering; D012038:Regeneration / Q000502:physiology; D020218:Response Elements / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D013997:Time Factors; D019459:Urothelium / Q000166:cytology / Q000378:metabolism*
C496499:FOXA1 protein, human; D051541:Hepatocyte Nuclear Factor 3-alpha; C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; D008562:Membrane Glycoproteins; D047495:PPAR gamma; D034741:RNA, Small Interfering; C512478:EGFR protein, human; D066246:ErbB Receptors