title: Nuclear receptor co-repressor is required to maintain proliferation of normal intestinal epithelial cells in culture and down-modulates the expression of pigment epithelium-derived factor.
abstract: Stem cells of the gut epithelium constantly produce precursors that progressively undergo a succession of molecular changes resulting in growth arrest and commitment to a specific differentiation program. Few transcriptional repressors have been identified that maintain the normal intestinal epithelial cell (IEC) proliferation state. Herein, we show that the nuclear receptor co-repressor (NCoR1) is differentially expressed during the proliferation-to-differentiation IEC transition. Silencing of NCoR1 expression in proliferating cells of crypt origin resulted in a rapid growth arrest without associated cell death. A genechip profiling analysis identified several candidate genes to be up-regulated in NCoR1-deficient IEC. Pigment epithelium-derived factor (PEDF, also known as serpinf1), a suspected tumor suppressor gene that plays a key role in the inhibition of epithelial tissue growth, was significantly up-regulated in these cells. Chromatin immunoprecipitation experiments showed that the PEDF gene promoter was occupied by NCoR1 in proliferating epithelial cells. Multiple retinoid X receptor (RXR) heterodimers interacting sites of the PEDF promoter were confirmed to interact with RXR and retinoid acid receptor (RAR). Cotransfection assays showed that RXR and RAR were able to transactivate the PEDF promoter and that NCoR1 was repressing this effect. Finally, forced expression of PEDF in IEC resulted in a slower rate of proliferation. These observations suggest that NCoR1 expression is required to maintain IEC in a proliferative state and identify PEDF as a novel transcriptional target for NCoR1 repressive action.
authors.affiliation: Département d'Anatomie et Biologie Cellulaire, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada.
authors.forename: Geneviève
authors.initials: G
authors.lastname: Doyon
authors.forename: Stéphanie
authors.initials: S
authors.lastname: St-Jean
authors.forename: Mathieu
authors.initials: M
authors.lastname: Darsigny
authors.forename: Claude
authors.initials: C
authors.lastname: Asselin
authors.forename: Francois
authors.initials: F
authors.lastname: Boudreau
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018938:Caco-2 Cells; D049109:Cell Proliferation; D004847:Epithelial Cells / Q000378:metabolism*; D005136:Eye Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D007422:Intestines / Q000166:cytology*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009414:Nerve Growth Factors / Q000378:metabolism*; D009687:Nuclear Proteins / Q000502:physiology*; D056971:Nuclear Receptor Co-Repressor 1; D051381:Rats; D012097:Repressor Proteins / Q000502:physiology*; D015843:Serpins / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D000099174:Pigment Epithelium-Derived Factor
chemical_list: D005136:Eye Proteins; D009414:Nerve Growth Factors; D009687:Nuclear Proteins; D056971:Nuclear Receptor Co-Repressor 1; D012097:Repressor Proteins; D015843:Serpins; D000099174:Pigment Epithelium-Derived Factor; C539127:NCOR1 protein, human; C539129:Ncor1 protein, rat