Sterol regulatory element binding protein 1a regulates hepatic fatty acid partitioning by activating acetyl coenzyme A carboxylase 2

Seung Soon Im, Linda E. Hammond, Leyla Yousef, Cherryl Nugas-Selby, Dong Ju Shin, Young Kyo Seo, Loren G. Fong, Stephen G. Young, Timothy F. Osborne

Research output: Contribution to journalArticle

Abstract

We generated a line of mice in which sterol regulatory element binding protein 1a (SREBP-1a) was specifically inactivated by insertional mutagenesis. Homozygous mutant mice were completely viable despite expressing SREBP-1a mRNA below 5% of normal, and there were minimal effects on expression of either SREBP-1c or -2. Microarray expression studies in liver, where SREBP-1a mRNA is 1/10 the level of the highly similar SREBP-1c, demonstrated that only a few genes were affected. The only downregulated genes directly linked to lipid metabolism were Srebf1 (which encodes SREBP-1) and Acacb (which encodes acetyl coenzyme A [acetyl-CoA] carboxylase 2 [ACC2], a critical regulator of fatty acyl-CoA partitioning between cytosol and mitochondria). ACC2 regulation is particularly important during food restriction. Similar to Acacb knockout mice, SREBP-1a-deficient mice have lower hepatic triglycerides and higher serum ketones during fasting than wild-type mice. SREBP-1a and -1c have identical DNA binding and dimerization domains; thus, the failure of the more abundant SREBP-1c to substitute for activating hepatic ACC2 must relate to more efficient recruitment of transcriptional coactivators to the more potent SREBP-1a activation domain. Our chromatin immunoprecipitation results support this hypothesis.

Original languageEnglish (US)
Pages (from-to)4864-4872
Number of pages9
JournalMolecular and cellular biology
Volume29
Issue number17
DOIs
StatePublished - Sep 1 2009

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ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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