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  • The EMBO Journal (2006) 25, 4490 - 4502
  • doi:10.1038/sj.emboj.7601332

Published online: 21 September 2006

Smads orchestrate specific histone modifications and chromatin remodeling to activate transcription

Sarah Ross1,a, Edwin Cheung2,3,a, Thodoris G Petrakis1, Michael Howell1, W Lee Kraus2 and Caroline S Hill1

  1. Laboratory of Developmental Signalling, Cancer Research UK London Research Institute, London, UK
  2. Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA
  3. Genome Institute of Singapore, Genome, Singapore

Correspondence to:

Caroline S Hill, Laboratory of Developmental Signalling, Cancer Research UK London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3PX, UK. Tel.: +44 20 7269 2941; Fax: +44 20 7269 3093; E-mail: caroline.hill@cancer.org.uk

aThese authors contributed equally to this work

Received 30 March 2006; Accepted 11 August 2006

Smads are intracellular transducers for TGF-beta superfamily ligands, but little is known about the mechanism by which complexes of receptor-phosphorylated Smad2 and Smad4 regulate transcription. Using an in vitro transcription system, we have discovered that, unlike most transcription factors that are sufficient to recruit the basal transcription machinery and therefore activate transcription on both naked DNA and chromatin templates, the Smads only activate transcription from chromatin templates. We demonstrate that Smad2-mediated transcription requires the histone acetyltransferase, p300. Smad2-recruited p300 exhibits an altered substrate specificity, specifically acetylating nucleosomal histone H3 at lysines 9 and 18, and these modifications are also detected on an endogenous Smad2-dependent promoter in a ligand-induced manner. Furthermore, we show that endogenous Smad2 interacts with the SWI/SNF ATPase, Brg1, in a TGF-beta-dependent manner, and demonstrate that Brg1 is recruited to Smad2-dependent promoters and is specifically required for TGF-beta-induced expression of endogenous Smad2 target genes. Our data indicate that the Smads define a new class of transcription factors that absolutely require chromatin to assemble the basal transcription machinery and activate transcription.

  • Keywords:

    • Brg1,
    • chromatin,
    • Smad,
    • TGF-beta,
    • transcription