SREBP-2, a second basic-helix-loop-helix-leucine zipper protein that stimulates transcription by binding to a sterol regulatory element

Xianxin Hua, Chieko Yokoyama, Jian Wu, Michael R. Briggs, Michael S. Brown, Joseph L. Goldstein, Xiaodong Wang

Research output: Contribution to journalArticle

456 Scopus citations

Abstract

We report the cDNA cloning of SREBP-2, the second member of a family of basic-helix-loop-helix-leucine zipper (bHLH-Zip) transcription factors that recognize sterol regulatory element 1 (SRE-1). SRE-1, a conditional enhancer in the promoters for the low density lipoprotein receptor and 3-hydroxy-3- methylglutaryl-coenzyme A synthase genes, increases transcription in the absence of sterols and is inactivated when sterols accumulate. Human SREBP-2 contains 1141 amino acids and is 47% identical to human SREBP-1a, the first recognized member of this family. The resemblance includes an acidic NH2 terminus, a highly conserved bHLH-Zip motif (71% identical), and an unusually long extension of 740 amino acids on the COOH-terminal side of the bHLH-Zip region. SREBP-2 possesses one feature lacking in SREBP-1a-namely, a glutamine-rich region (27% glutamine over 121 residues). In vitro SREBP-2 bound SRE-1 with the same specificity as SREBP-1a. In vivo it mimicked SREBP- 1a in activating transcription of reporter genes containing SRE-1. As with SREBP-1a, activation by SREBP-2 occurred in the absence and presence of sterols, abolishing regulation. Cotransfection of low amounts of pSREBP-1a and pSREBP-2 into human embryonic kidney 293 cells stimulated transcription of promoters containing SRE-1 in an additive fashion. At high levels transcription reached a maximum, and the effects were no longer additive. The reason for the existence of two SREBPs and the mechanism by which they are regulated by sterols remain to be determined.

Original languageEnglish (US)
Pages (from-to)11603-11607
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume90
Issue number24
DOIs
StatePublished - Dec 29 1993

Keywords

  • 3-hydroxy-3- methylglutaryl-coenzyme A synthase
  • cDNA cloning
  • cholesterol
  • low density lipoprotein receptor

ASJC Scopus subject areas

  • General

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