Publications (2)12.8 Total impact
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Article: Structure of the 30-kDa Sin3-associated protein (SAP30) in complex with the mammalian Sin3A corepressor and its role in nucleic acid binding.
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ABSTRACT: The ∼2-megadalton evolutionarily conserved histone deacetylase-associated Rpd3L/Sin3L complex plays critical roles in altering the histone code and repressing transcription of a broad range of genes involved in many aspects of cellular physiology. Targeting of this complex to specific regions of the genome is presumed to rely on interactions involving one or more of at least 10 distinct subunits in the complex. Here we describe the solution structure of the complex formed by the interacting domains of two constitutively associated subunits, mSin3A and SAP30. The mSin3A paired amphipathic helix 3 (PAH3) domain in the complex adopts the left-handed four-helix bundle structure characteristic of PAH domains. The SAP30 Sin3 interaction domain (SID) binds to PAH3 via a tripartite structural motif, including a C-terminal helix that targets the canonical PAH hydrophobic cleft while two other helices and an N-terminal extension target a discrete surface formed largely by the PAH3 α2, α3, and α3' helices. The protein-protein interface is extensive (∼1400 Å(2)), accounting for the high affinity of the interaction and the constitutive association of the SAP30 subunit with the Rpd3L/Sin3L complex. We further show using NMR that the mSin3A PAH3-SAP30 SID complex can bind to nucleic acids, hinting at a role for a nucleolar localization sequence in the SID αA helix in targeting the Rpd3L/Sin3L complex for silencing ribosomal RNA genes.Journal of Biological Chemistry 06/2011; 286(31):27814-24. · 4.77 Impact Factor -
Article: Solution structure of a novel zinc finger motif in the SAP30 polypeptide of the Sin3 corepressor complex and its potential role in nucleic acid recognition.
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ABSTRACT: Giant chromatin-modifying complexes regulate gene transcription in eukaryotes by acting on chromatin substrates and 'setting' the histone code. The histone deacetylase (HDAC)-associated mammalian Sin3 corepressor complex regulates a wide variety of genes involved in all aspects of cellular physiology. The recruitment of the corepressor complex by transcription factors to specific regions of the genome is mediated by Sin3 as well as 10 distinct polypeptides that comprise the corepressor complex. Here we report the solution structure of a novel CCCH zinc finger (ZnF) motif in the SAP30 polypeptide, a key component of the corepressor complex. The structure represents a novel fold comprising two beta-strands and two alpha-helices with the zinc organizing center showing remote resemblance to the treble clef motif. In silico analysis of the structure revealed a highly conserved surface that is dominated by basic residues. NMR-based analysis of potential ligands for the SAP30 ZnF motif indicated a strong preference for nucleic acid substrates. We propose that the SAP30 ZnF functions as a double-stranded DNA-binding motif, thereby expanding the known functions of both SAP30 and the mammalian Sin3 corepressor complex. Our results also call into question the common assumption about the exclusion of DNA-binding core subunits within chromatin-modifying/remodeling complexes.Nucleic Acids Research 03/2009; 37(7):2142-52. · 8.03 Impact Factor
