Isoform 1c of sterol regulatory element binding protein is less active than isoform 1a in livers of transgenic mice and in cultured cells. (original) (raw)
- Journal List
- J Clin Invest
- v.99(5); 1997 Mar 1
- PMC507891
J Clin Invest. 1997 Mar 1; 99(5): 846–854.
Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas 75235, USA.
Abstract
We have produced transgenic mice whose livers express a dominant positive NH2-terminal fragment of sterol regulatory element binding protein-1c (SREBP-1c). Unlike full-length SREBP-1c, the NH2-terminal fragment enters the nucleus without a requirement for proteolytic release from cell membranes, and hence it is immune to downregulation by sterols. We compared SREBP-1c transgenic mice with a line of transgenic mice that produces an equal amount of the NH2-terminal fragment of SREBP-1a. SREBP-1a and -1c are alternate transcripts from a single gene that differ in the first exon, which encodes part of an acidic activation domain. The 1a protein contains a long activation domain with 12 negatively charged amino acids, whereas the 1c protein contains a short activation domain with only 6 such amino acids. As previously reported, livers of the SREBP-1a transgenic mice were massively enlarged, owing to accumulation of triglycerides and cholesterol. SREBP-1c transgenic livers were only slightly enlarged with only a moderate increase in triglycerides, but not cholesterol. The mRNAs for the LDL receptor and several cholesterol biosynthetic enzymes were elevated in SREBP-la transgenic mice, but not in 1c transgenic mice. The mRNAs for fatty acid synthase and acetyl CoA carboxylase were elevated 9- and 16-fold in la animals, but only 2- and 4-fold in 1c animals. Experiments with transfected cells confirmed that SREBP-1c is a much weaker activator of transcription than SREBP-1a when both are expressed at levels approximating those found in nontransfected cells. SREBP-1c became a strong activator only when expressed at supraphysiologic levels. We conclude that SREBP-1a is the most active form of SREBP-1 and that SREBP-1c may be produced when cells require a lower rate of transcription of genes regulating cholesterol and fatty acid metabolism.
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Selected References
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- Wang X, Sato R, Brown MS, Hua X, Goldstein JL. SREBP-1, a membrane-bound transcription factor released by sterol-regulated proteolysis. Cell. 1994 Apr 8;77(1):53–62. [PubMed] [Google Scholar]
- Shimano H, Horton JD, Hammer RE, Shimomura I, Brown MS, Goldstein JL. Overproduction of cholesterol and fatty acids causes massive liver enlargement in transgenic mice expressing truncated SREBP-1a. J Clin Invest. 1996 Oct 1;98(7):1575–1584. [PMC free article] [PubMed] [Google Scholar]
- Kim JB, Spiegelman BM. ADD1/SREBP1 promotes adipocyte differentiation and gene expression linked to fatty acid metabolism. Genes Dev. 1996 May 1;10(9):1096–1107. [PubMed] [Google Scholar]
- Ericsson J, Jackson SM, Lee BC, Edwards PA. Sterol regulatory element binding protein binds to a cis element in the promoter of the farnesyl diphosphate synthase gene. Proc Natl Acad Sci U S A. 1996 Jan 23;93(2):945–950. [PMC free article] [PubMed] [Google Scholar]
- Bennett MK, Lopez JM, Sanchez HB, Osborne TF. Sterol regulation of fatty acid synthase promoter. Coordinate feedback regulation of two major lipid pathways. J Biol Chem. 1995 Oct 27;270(43):25578–25583. [PubMed] [Google Scholar]
- Yokoyama C, Wang X, Briggs MR, Admon A, Wu J, Hua X, Goldstein JL, Brown MS. SREBP-1, a basic-helix-loop-helix-leucine zipper protein that controls transcription of the low density lipoprotein receptor gene. Cell. 1993 Oct 8;75(1):187–197. [PubMed] [Google Scholar]
- Hua X, Wu J, Goldstein JL, Brown MS, Hobbs HH. Structure of the human gene encoding sterol regulatory element binding protein-1 (SREBF1) and localization of SREBF1 and SREBF2 to chromosomes 17p11.2 and 22q13. Genomics. 1995 Feb 10;25(3):667–673. [PubMed] [Google Scholar]
- Shimomura I, Shimano H, Horton JD, Goldstein JL, Brown MS. Differential expression of exons 1a and 1c in mRNAs for sterol regulatory element binding protein-1 in human and mouse organs and cultured cells. J Clin Invest. 1997 Mar 1;99(5):838–845. [PMC free article] [PubMed] [Google Scholar]
- Hua X, Yokoyama C, Wu J, Briggs MR, Brown MS, Goldstein JL, Wang X. SREBP-2, a second basic-helix-loop-helix-leucine zipper protein that stimulates transcription by binding to a sterol regulatory element. Proc Natl Acad Sci U S A. 1993 Dec 15;90(24):11603–11607. [PMC free article] [PubMed] [Google Scholar]
- Sato R, Yang J, Wang X, Evans MJ, Ho YK, Goldstein JL, Brown MS. Assignment of the membrane attachment, DNA binding, and transcriptional activation domains of sterol regulatory element-binding protein-1 (SREBP-1). J Biol Chem. 1994 Jun 24;269(25):17267–17273. [PubMed] [Google Scholar]
- Yang J, Sato R, Goldstein JL, Brown MS. Sterol-resistant transcription in CHO cells caused by gene rearrangement that truncates SREBP-2. Genes Dev. 1994 Aug 15;8(16):1910–1919. [PubMed] [Google Scholar]
- Hua X, Sakai J, Ho YK, Goldstein JL, Brown MS. Hairpin orientation of sterol regulatory element-binding protein-2 in cell membranes as determined by protease protection. J Biol Chem. 1995 Dec 8;270(49):29422–29427. [PubMed] [Google Scholar]
- Hua X, Sakai J, Brown MS, Goldstein JL. Regulated cleavage of sterol regulatory element binding proteins requires sequences on both sides of the endoplasmic reticulum membrane. J Biol Chem. 1996 Apr 26;271(17):10379–10384. [PubMed] [Google Scholar]
- Sakai J, Duncan EA, Rawson RB, Hua X, Brown MS, Goldstein JL. Sterol-regulated release of SREBP-2 from cell membranes requires two sequential cleavages, one within a transmembrane segment. Cell. 1996 Jun 28;85(7):1037–1046. [PubMed] [Google Scholar]
- Guan G, Jiang G, Koch RL, Shechter I. Molecular cloning and functional analysis of the promoter of the human squalene synthase gene. J Biol Chem. 1995 Sep 15;270(37):21958–21965. [PubMed] [Google Scholar]
- Yieh L, Sanchez HB, Osborne TF. Domains of transcription factor Sp1 required for synergistic activation with sterol regulatory element binding protein 1 of low density lipoprotein receptor promoter. Proc Natl Acad Sci U S A. 1995 Jun 20;92(13):6102–6106. [PMC free article] [PubMed] [Google Scholar]
- Briggs MR, Yokoyama C, Wang X, Brown MS, Goldstein JL. Nuclear protein that binds sterol regulatory element of low density lipoprotein receptor promoter. I. Identification of the protein and delineation of its target nucleotide sequence. J Biol Chem. 1993 Jul 5;268(19):14490–14496. [PubMed] [Google Scholar]
- Ericsson J, Jackson SM, Edwards PA. Synergistic binding of sterol regulatory element-binding protein and NF-Y to the farnesyl diphosphate synthase promoter is critical for sterol-regulated expression of the gene. J Biol Chem. 1996 Oct 4;271(40):24359–24364. [PubMed] [Google Scholar]
- Tontonoz P, Kim JB, Graves RA, Spiegelman BM. ADD1: a novel helix-loop-helix transcription factor associated with adipocyte determination and differentiation. Mol Cell Biol. 1993 Aug;13(8):4753–4759. [PMC free article] [PubMed] [Google Scholar]
- Vallett SM, Sanchez HB, Rosenfeld JM, Osborne TF. A direct role for sterol regulatory element binding protein in activation of 3-hydroxy-3-methylglutaryl coenzyme A reductase gene. J Biol Chem. 1996 May 24;271(21):12247–12253. [PubMed] [Google Scholar]
- Kim JB, Spotts GD, Halvorsen YD, Shih HM, Ellenberger T, Towle HC, Spiegelman BM. Dual DNA binding specificity of ADD1/SREBP1 controlled by a single amino acid in the basic helix-loop-helix domain. Mol Cell Biol. 1995 May;15(5):2582–2588. [PMC free article] [PubMed] [Google Scholar]
- Yang J, Brown MS, Ho YK, Goldstein JL. Three different rearrangements in a single intron truncate sterol regulatory element binding protein-2 and produce sterol-resistant phenotype in three cell lines. Role of introns in protein evolution. J Biol Chem. 1995 May 19;270(20):12152–12161. [PubMed] [Google Scholar]
- Sheng Z, Otani H, Brown MS, Goldstein JL. Independent regulation of sterol regulatory element-binding proteins 1 and 2 in hamster liver. Proc Natl Acad Sci U S A. 1995 Feb 14;92(4):935–938. [PMC free article] [PubMed] [Google Scholar]
- Hua X, Nohturfft A, Goldstein JL, Brown MS. Sterol resistance in CHO cells traced to point mutation in SREBP cleavage-activating protein. Cell. 1996 Nov 1;87(3):415–426. [PubMed] [Google Scholar]
- Smith JR, Osborne TF, Brown MS, Goldstein JL, Gil G. Multiple sterol regulatory elements in promoter for hamster 3-hydroxy-3-methylglutaryl-coenzyme A synthase. J Biol Chem. 1988 Dec 5;263(34):18480–18487. [PubMed] [Google Scholar]
- Südhof TC, Russell DW, Brown MS, Goldstein JL. 42 bp element from LDL receptor gene confers end-product repression by sterols when inserted into viral TK promoter. Cell. 1987 Mar 27;48(6):1061–1069. [PubMed] [Google Scholar]
- Andersson S, Davis DL, Dahlbäck H, Jörnvall H, Russell DW. Cloning, structure, and expression of the mitochondrial cytochrome P-450 sterol 26-hydroxylase, a bile acid biosynthetic enzyme. J Biol Chem. 1989 May 15;264(14):8222–8229. [PubMed] [Google Scholar]
- Amy CM, Williams-Ahlf B, Naggert J, Smith S. Molecular cloning of the mammalian fatty acid synthase gene and identification of the promoter region. Biochem J. 1990 Nov 1;271(3):675–679. [PMC free article] [PubMed] [Google Scholar]
- Chang SF, Netter HJ, Will H. Characterization of cDNA encoding the mouse hepatic triglyceride lipase and expression by in vitro translation. FEBS Lett. 1991 Sep 2;289(1):69–72. [PubMed] [Google Scholar]
- Smith JR, Osborne TF, Goldstein JL, Brown MS. Identification of nucleotides responsible for enhancer activity of sterol regulatory element in low density lipoprotein receptor gene. J Biol Chem. 1990 Feb 5;265(4):2306–2310. [PubMed] [Google Scholar]
- Oliner JD, Andresen JM, Hansen SK, Zhou S, Tjian R. SREBP transcriptional activity is mediated through an interaction with the CREB-binding protein. Genes Dev. 1996 Nov 15;10(22):2903–2911. [PubMed] [Google Scholar]
- Ayer DE, Kretzner L, Eisenman RN. Mad: a heterodimeric partner for Max that antagonizes Myc transcriptional activity. Cell. 1993 Jan 29;72(2):211–222. [PubMed] [Google Scholar]
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