Sterol-dependent repression of low density lipoprotein receptor promoter mediated by 16-base pair sequence adjacent to binding site for transcription factor Sp1

P. A. Dawson, S. L. Hofmann, D. R. Van der Westhuyzen, T. C. Sudhof, M. S. Brown, J. L. Goldstein

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A 42-base pair sequence from the 5' flanking region of the low density lipoprotein receptor gene was shown previously to confer sensitivity to sterol-mediated repression when inserted into the herpes simplex virus thymidine kinase promoter. This sequence contains two contiguous 16-base pair repeats, designated repeats 2 and 3, which differ from each other at four positions. In the current study we have analyzed separately the functions of repeats 2 and 3 by altering their sequences, inserting them into the -60 position of the thymidine kinase promoter, and introducing the hybrid promoters into hamster cells by transfection. These studies show that repeat 3 is a constitutive positive transcriptional element that acts in the absence or presence of sterols. Repeat 2 confers strong repression upon repeat 3 when sterols are present. In vitro DNase footprinting and gel retardation assays show that repeat 3, but not repeat 2, binds purified Sp1, a positive transcription factor. Mutants of repeat 3 that abolish transcriptional activity in vivo abolish Sp1 binding in vitro. We suggest that the low density lipoprotein receptor is regulated by a push-pull mechanism in which sterol-regulated binding of a protein to repeat 2 silences the activity of the adjacent Sp1-binding site in repeat 3.

Original languageEnglish (US)
Pages (from-to)3372-3379
Number of pages8
JournalJournal of Biological Chemistry
Issue number7
Publication statusPublished - 1988


ASJC Scopus subject areas

  • Biochemistry

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