Factor recruitment and TIF2/GRIP1 corepressor activity at a collagenase-3 response element that mediates regulation by phorbol esters and hormones.
To investigate determinants of specific transcriptional regulation, we measured factor occupancy and function at a response element, col3A, associated with the collagenase-3 gene in human U2OS osteosarcoma cells; col3A confers activation by phorbol esters, and repression by glucocorticoid and thyroid hormones. The subunit composition and activity of AP-1, which binds col3A, paralleled the intracellular level of cFos, which is modulated by phorbol esters and glucocorticoids. In contrast, a similar AP-1 site at the collagenase-1 gene, not inducible in U2OS cells, was not bound by AP-1. The glucocorticoid receptor (GR) associated with col3A through protein-protein interactions with AP-1, regardless of AP-1 subunit composition, and repressed transcription. TIF2/GRIP1, reportedly a coactivator for GR and the thyroid hormone receptor (TR), was recruited to col3A and potentiated GR-mediated repression in the presence of a GR agonist but not antagonist. GRIP1 mutants deficient in GR binding and coactivator functions were also defective for corepression, and a GRIP1 fragment containing the GR-interacting region functioned as a dominant-negative for repression. In contrast, repression by TR was unaffected by GRIP1. Thus, the composition of regulatory complexes, and the biological activities of the bound factors, are dynamic and dependent on cell and response element contexts. Cofactors such as GRIP1 probably contain distinct surfaces for activation and repression that function in a context-dependent manner.
Rogatsky
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Department of Cellular and Molecular Pharmacology, University of California, 513 Parnassus Avenue, HSW1201, San Francisco, CA 94143-0450, USA.
Zarember
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Yamamoto
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D000818:Animals; D017364:Collagenases / Q000096:biosynthesis / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000502:physiology*; D006727:Hormone Antagonists / Q000494:pharmacology; D006728:Hormones / Q000494:pharmacology; D006801:Humans; D053509:Matrix Metalloproteinase 13; D051379:Mice; D015735:Mifepristone / Q000494:pharmacology; D051958:Nuclear Receptor Coactivator 2; D012516:Osteosarcoma / Q000378:metabolism*; D010703:Phorbol Esters / Q000494:pharmacology; D011485:Protein Binding / Q000502:physiology; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D011988:Receptors, Thyroid Hormone / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D020218:Response Elements / Q000187:drug effects / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D006727:Hormone Antagonists; D006728:Hormones; C498001:NCOA2 protein, human; C498002:Ncoa2 protein, mouse; C498003:Ncoa2 protein, rat; D051958:Nuclear Receptor Coactivator 2; D010703:Phorbol Esters; D011965:Receptors, Glucocorticoid; D011988:Receptors, Thyroid Hormone; D012097:Repressor Proteins; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D015735:Mifepristone; D017364:Collagenases; C507079:MMP13 protein, human; D053509:Matrix Metalloproteinase 13; C507081:Mmp13 protein, mouse; C507083:Mmp13 protein, rat