HBP1 and Mad1 repressors bind the Sin3 corepressor PAH2 domain with opposite helical orientations

Kurt A. Swanson, Paul S Knoepfler, Kai Huang, Richard S. Kang, Shaun M. Cowley, Carol D. Laherty, Robert N. Eisenman, Ishwar Radhakrishnan

Research output: Contribution to journalArticlepeer-review

60 Scopus citations


Recruitment of the histone deacetylase (HDAC)-associated Sin3 corepressor is an obligatory step in many eukaryotic gene silencing pathways. Here we show that HBP1, a cell cycle inhibitor and regulator of differentiation, represses transcription in a HDAC/Sin3-dependent manner by targeting the mammalian Sin3A (mSin3A) PAH2 domain. HBP1 is unrelated to the Mad1 repressor for which high-resolution structures in complex with PAH2 have been described. We show that like Mad1, the HBP1 transrepression domain binds through a helical structure to the hydrophobic cleft of mSin3A PAH2. Notably, the HBP1 helix binds PAH2 in a reversed orientation relative to Mad1 and, equally unexpectedly, this is correlated with a chain reversal of the minimal Sin3 interaction motifs. These results not only provide insights into how multiple, unrelated transcription factors recruit the same coregulator, but also have implications for how sequence similarity searches are conducted.

Original languageEnglish (US)
Pages (from-to)738-746
Number of pages9
JournalNature Structural and Molecular Biology
Issue number8
StatePublished - Aug 2004
Externally publishedYes

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology


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