Identification of Conserved cis-Elements and Transcription Factors Required for Sterol-regulated Transcription of Stearoyl-CoA Desaturase 1 and 2

Abstract

We previously identified stearoyl-CoA desaturase 2 (SCD2) as a new member of the family of genes that are transcriptionally regulated in response to changing levels of nuclear sterol regulatory element binding proteins (SREBPs) or adipocyte determination and differentiation factor 1 (ADD1). A novel sterol regulatory element (SRE) (5-AGCAGATTGTG-3) identified in the proximal promoter of the mouse SCD2 gene is required for induction of SCD2 promoter-reporter genes in response to cellular sterol depletion (Tabor, D. E., Kim, J. B., Spiegelman, B. M., and Edwards, P. A. (1998) J. Biol. Chem. 273, 22052-22058).In this report, we demonstrate that this novel SRE is both present in the promoter of the SCD1 gene and is critical for the sterol-dependent transcription of SCD1 promoter-reporter genes. Two conserved cis elements (5-CCAAT-3) lie 5 and 48 base pairs 3 of the novel SREs in the promoters of both the SCD1 and SCD2 murine genes. Mutation of either of these putative NF-Y binding sites attenuates the transcriptional activation of SCD1 or SCD2 promoter-reporter genes in response to cellular sterol deprivation. Induction of both reporter genes is also attenuated when cells are cotransfected with dominant-negative forms of either NF-Y or SREBP. In addition, we demonstrate that the induction of SCD1 and SCD2 mRNAs that occurs during the differentiation of 3T3-L1 preadipocytes to adipocytes is paralleled by an increase in the levels of ADD1/SREBP-1c and that the SCD1 and SCD2 mRNAs are induced to even higher levels in response to ectopic expression of ADD1/SREBP-1c. We conclude that transcription of both SCD1 and SCD2 genes is responsive to cellular sterol levels and to the levels of nuclear SREBP/ADD1 and that transcriptional induction requires three spatially conserved cis elements, that bind SREBP and NF-Y. Additional studies demonstrate that maximal transcriptional repression of SCD2 reporter genes in response to an exogenous polyunsaturated fatty acid is dependent upon the SRE and the adjacent CCAAT motif.

Stearoyl-CoA Desaturase 1 Gene Expression Is Necessary for Fructose-mediated Induction of Lipogenic Gene Expression by Sterol Regulatory Element-binding Protein-1c-dependent and -independent Mechanisms

“…1 and 5). These data suggested that the induction of SCD1 and other lipogenic genes is dependent on SREBP-1c expression and would be consistent with published reports (32)(33)(34). However, using SREBP-1cϪ/Ϫ mice, we found that, unlike in short term feeding (data not shown), the long term feeding of fructose induced SCD1, ACC, and FAS mRNA to levels comparable to the levels induced by fructose in the wild-type mice (Fig.…”

“…In a minor pathway, oleate mediates the induction of SREBP-1c expression and maturation, which in turn induces the expression of lipogenic genes consistent with published reports (34 -39, 57, 60, 61). SREBP-1c in a feedback loop can induce SCD1 gene expression by its capacity to bind to the sterol regulatory element present in the SCD promoter (32,33), resulting in the production of more oleate. As a major pathway, oleate mediates maximum induction of lipogenic gene expression by fructose in an SREBP-1c-independent manner.…”

“…The SCD1 gene is regulated at the transcriptional level by a number of dietary factors including cholesterol, polyunsaturated fatty acids, glucose, and fructose (27)(28)(29)(30)(31) in a sterol regulatory element-binding protein-1c (SREBP-1c)-dependent mechanism (32)(33)(34). Sterol regulatory element-binding proteins are members of the basic helix-loop-helix leucine zipper family of transcription factors and regulate enzymes responsible for the synthesis of cholesterol, fatty acids, and triglycerides (35).…”

Human White/Murine ABC8 mRNA Levels Are Highly Induced in Lipid-loaded Macrophages

“…Cholesterol was from steraloids and oxysterols from Sigma. The sources of all other reagents and plasmids have been given (41,42).…”

The adipose conversion process: regulation by extracellular and intracellular factors

“…In addition, adipocyte determination and differentiation factor 1/sterol regulatory elementbinding protein 1 (ADD1/SREBP1), a member of the bHLH (basic region/helixloop-helix domain protein) family, is known to induce genes implicated in the FA metabolism (e.g., types 1 and 2 stearoylCoA desaturase genes) by binding on specific DNA binding sites, such as the E-box, a helix-loop-helix consensus sequence, and the sterol response element [51,69,228,237]. A model of action for C/EBPs, PPARγ and ADD1/SREBP1 has been proposed [69,156].…”