Activation of TM7SF2 promoter by SREBP-2 depends on a new sterol regulatory element, a GC-box, and an inverted CCAAT-box
TM7SF2 gene encodes 3β-hydroxysterol Δ 14-reductase, responsible for the reduction of C14-unsaturated sterols in cholesterol biosynthesis. TM7SF2 gene expression is controlled by cell sterol levels through the SREBP-2. The motifs of TM7SF2 promoter responsible for activation by SREBP-2 have not been...
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Published in | Biochimica et biophysica acta Vol. 1801; no. 5; pp. 587 - 592 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
Netherlands
Elsevier B.V
01.05.2010
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Subjects | |
Online Access | Get full text |
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Summary: | TM7SF2 gene encodes 3β-hydroxysterol Δ
14-reductase, responsible for the reduction of C14-unsaturated sterols in cholesterol biosynthesis.
TM7SF2 gene expression is controlled by cell sterol levels through the SREBP-2. The motifs of
TM7SF2 promoter responsible for activation by SREBP-2 have not been characterized. Using electrophoretic mobility shift assays and mutation analysis, we identified a new SRE motif, 60% identical to an inverted SRE-3, able to bind SREBP-2 in vitro and in vivo. Co-transfection of promoter–luciferase reporter constructs in HepG2 cells showed that the binding of SREBP-2 to SRE produced approximately 26-fold promoter activation, whereas mutation of the SRE motif caused a dramatic decrease of transactivation by SREBP-2. The function of additional motifs that bind transcription factors cooperating with SREBP-2 was investigated. An inverted CCAAT-box, that binds nuclear factor Y (NF-Y), cooperates with SREBP-2 in
TM7SF2 promoter activation. Deletion of this motif resulted in the loss of promoter induction by sterol starvation in HepG2 cells, as well as a decrease in fold activation by SREBP-2 in co-transfection experiments. Moreover, co-transfection of the promoter with a plasmid expressing dominant negative NF-YA did not permit full activation by SREBP-2. Three GC-boxes (1, 2, 3), known to bind Sp1 transcription factor, were also investigated. The mutagenesis of each of them produced a decrease in SREBP-2-dependent activation, the most powerful being GC-box2. A triple mutagenized promoter construct did not have an additive effect. We conclude that, besides the SRE motif, both the inverted CCAAT-box and GC-box2 are essential for full promoter activation by SREBP-2. |
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ISSN: | 1388-1981 0006-3002 1879-2618 |
DOI: | 10.1016/j.bbalip.2010.01.013 |