Role of an mSin3A-Swi/Snf chromatin remodeling complex in the feedback repression of bile acid biosynthesis by SHP.
The orphan receptor SHP interacts with many nuclear receptors and inhibits their transcriptional activities. SHP is central to feedback repression of cholesterol 7alpha hydroxylase gene (CYP7A1) expression by bile acids, which is critical for maintaining cholesterol homeostasis. Using CYP7A1 as a model system, we studied the molecular mechanisms of SHP repression at the level of native chromatin. Chromatin immunoprecipitation studies showed that mSin3A and a Swi/Snf complex containing Brm as a central ATPase were recruited to the promoter. This recruitment was associated with chromatin remodeling after bile acid treatment that was blunted by inhibition of the endogenous Swi/Snf function by dominant-negative ATPase mutants. Biochemical studies indicated that SHP was associated with the mSin3A-Swi/Snf complex by direct interaction with Brm and mSin3A through its repression domain. Expression of Brm, but not an ATPase mutant, inhibited CYP7A1 promoter activity and further enhanced SHP-mediated repression. Bile acid-induced recruitment of mSin3A/Brm, chromatin remodeling, and concomitant repression of endogenous CYP7A1 expression were impaired when SHP expression was inhibited by SHP small interfering RNA. Our results suggest that SHP mediates recruitment of mSin3A-Swi/Snf to the CYP7A1 promoter, resulting in chromatin remodeling and gene repression, which may also be a mechanism for the repression by SHP of genes activated by many nuclear receptors. Our study establishes the first link between a Swi/Snf complex and regulation of cholesterol metabolism.
Kemper
Jongsook Kim
JK
Department of Molecular and Integrative Physiology, University of Illinois, Urbana, IL 61801, USA. jongsook@uiuc.edu
Kim
Hwajin
H
Miao
Ji
J
Bhalla
Sonali
S
Bae
Yangjin
Y
D000123:Acetyltransferases / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D001647:Bile Acids and Salts / Q000096:biosynthesis*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D002790:Cholesterol 7-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins; D025461:Feedback, Physiological; D005786:Gene Expression Regulation; D051548:Histone Acetyltransferases; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D046911:Macromolecular Substances; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D056264:Sin3 Histone Deacetylase and Corepressor Complex; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D001647:Bile Acids and Salts; D018797:Cell Cycle Proteins; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D029721:Drosophila Proteins; D046911:Macromolecular Substances; D018160:Receptors, Cytoplasmic and Nuclear; D012097:Repressor Proteins; C099683:SIN3A transcription factor; D015534:Trans-Activators; D014157:Transcription Factors; C086469:brm protein, Drosophila; C099713:nuclear receptor subfamily 0, group B, member 2; D002790:Cholesterol 7-alpha-Hydroxylase; D000123:Acetyltransferases; D051548:Histone Acetyltransferases; C110550:HDAC1 protein, human; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases; D056264:Sin3 Histone Deacetylase and Corepressor Complex; D000251:Adenosine Triphosphatases