DNA-Binding and -Bending Activities of SAP30L and SAP30 Are Mediated by a Zinc-Dependent Module and Monophosphoinositides

Abstract

Deacetylation of histones is carried out by a corepressor complex in which Sin3A is an essential scaffold protein. Two proteins in this complex, the Sin3A-associated proteins SAP30L and SAP30, have previously been suggested to function as linker molecules between various corepressors. In this report, we demonstrate new functions for human SAP30L and SAP30 by showing that they can associate directly with core histones as well as naked DNA. A zinc-coordinating structure is necessary for DNA binding, one consequence of which is bending of the DNA. We provide evidence that a sequence motif previously shown to be a nuclear localization signal is also a phosphatidylinositol (PI)-binding element and that binding of specific nuclear monophosphoinositides regulates DNA binding and chromatin association of SAP30L. PI binding also decreases the repression activity of SAP30L and affects its translocation from the nucleus to the cytoplasm. Our results suggest that SAP30L and SAP30 play active roles in recruitment of deacetylating enzymes to nucleosomes, and mediate key protein-protein and protein-DNA interactions involved in chromatin remodeling and transcription.

Redox‐dependent disulfide bond formation in SAP30L corepressor protein: Implications for structure and function

“…1(A)], two class I HDACs (HDAC1 and HDAC2), two histone-binding proteins (RBBP4/ RbAp46 and RBBP7/RbAp48) and, at least, seven Sin3A-associated proteins (SAP25, SAP30, SAP30L, SAP45/SUDS3, SAP130, SAP180/ARID4B, and RBBP1/ARID4A), whose functions are largely unknown. 9,11,12 The Sin3A complex regulates a wide variety of genes involved in a number of cellular processes. The complex is among the very few mammalian corepressor complexes that have been characterized so far.…”

“…SAP30L was originally discovered from T84 cells induced to differentiate by transforming growth factor b (TGF-b), and was further characterized to interact with DNA and histones 2A/2B as well as signaling phospholipids. 11,13 SAP30 and SAP30L (collectively known as SAP30 proteins) are evolutionarily highly conserved, and the genes of both proteins can be found from many different organisms. In previous studies, it has been suggested that SAP30 proteins have roles as stabilizing and bridging molecules in the Sin3A complex.…”

“…Apart from directly binding to DNA and nuclear signaling lipids, they can also interact with several other corepressors and transcription factors. 9,11,14 Previous experiments and truncation assays have indicated that the paired amphipatic helix 3/4 (PAH3/PAH4) regions in Sin3A are essential for gene repression. 14 SAP30 and SAP30L have been shown to mainly associate with the PAH3 domain of Sin3A.…”

“…S1) that is necessary for protein folding and function. 11,23 The ZnF motif is almost identical in SAP30 and SAP30L, containing exactly the same four zinc coordinating amino acid residues (Cys29, Cys38, Cys74 and His77 in SAP30L; for the corresponding residues in SAP30, see Supporting Information Fig. S1).…”

“…S1). 11 The ZnF motif in both SAP30 and SAP30L is a key element for the repression activity of the Sin3A complex. The ZnF motif in SAP30L mainly comprises residues 25-77 (Fig.…”