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Methods to Discover Alternative Promoter Usage and Transcriptional Regulation of Murine Bcrp1
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TBL1 and TBLR1 phosphorylation on regulated gene promoters overcomes dual CtBP and NCoR/SMRT transcriptional

Valentina Perissi1, Claudio Scafoglio, Jie Zhang

  • 1Howard Hughes Medical Institute, School of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.

Molecular Cell
|April 1, 2008
PubMed

Insights

Gene expression regulation in eukaryotes involves a dual-repression checkpoint. Transducer beta-like proteins TBL1 and TBLR1 release corepressors CtBP1/2 and NCoR/SMRT, enabling gene activation through specific phosphorylation.

Area of Science:

  • Molecular Biology
  • Gene Regulation
  • Epigenetics

Background:

  • Regulated gene expression in eukaryotes relies on controlling corepressor dismissal.
  • Signal-independent activation must be prevented for precise gene control.

Purpose of the Study:

  • To investigate the mechanism of dual-repression checkpoints in eukaryotic gene expression.
  • To identify the factors responsible for releasing distinct corepressor complexes.

Main Methods:

  • Analysis of signaling pathways including Notch, NF-kappaB, and nuclear receptor ligands.
  • Investigated the roles of transducer beta-like proteins (TBL1 and TBLR1) in corepressor release.
  • Examined the impact of specific phosphorylation sites on protein function.

Main Results:

  • Many signaling pathways utilize a dual-repression checkpoint involving CtBP1/2 and NCoR/SMRT corepressors.
  • TBL1 and TBLR1 act as exchange factors, facilitating ubiquitylation and degradation of CtBP1/2 and NCoR/SMRT, respectively.
  • Differential specificity of TBL1/TBLR1 is determined by five Ser/Thr phosphorylation site differences, regulated by upstream signaling.

Conclusions:

  • Dual-factor repression checkpoints ensure regulated gene expression by controlling distinct corepressor complexes.
  • TBL1 and TBLR1 function as signal-specific sensors for corepressor dismissal.
  • Upstream signaling pathways impose specificity on corepressor release through phosphorylation of exchange factors.

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