Yang Xiaofang, Zaurin Roser, Beato Miguel, Peterson Craig L
Interdisciplinary Graduate Program, Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
Nat Struct Mol Biol. 2007 Jun;14(6):540-7. doi: 10.1038/nsmb1238. Epub 2007 May 13.
Yeast SWI/SNF is a multisubunit, 1.14-MDa ATP-dependent chromatin-remodeling enzyme required for transcription of a subset of inducible genes. Biochemical studies have demonstrated that SWI/SNF uses the energy from ATP hydrolysis to generate superhelical torsion, mobilize mononucleosomes, enhance the accessibility of nucleosomal DNA and remove H2A-H2B dimers from mononucleosomes. Here we describe the ATP-dependent activities of a SWI/SNF sub complex that is composed of only three subunits, Swi2p, Arp7p and Arp9p. Whereas this sub complex is fully functional in most remodeling assays, Swi2p-Arp7p-Arp9p is defective for ATP-dependent removal of H2A-H2B dimers. We identify the acidic N terminus of the Swi3p subunit as a novel H2A-H2B-binding domain required for ATP-dependent dimer loss. Our data indicate that H2A-H2B dimer loss is not an obligatory consequence of ATP-dependent DNA translocation, and furthermore they suggest that SWI/SNF is composed of at least four interdependent modules.
酵母SWI/SNF是一种多亚基、1.14兆道尔顿的ATP依赖型染色质重塑酶，是一组可诱导基因转录所必需的。生化研究表明，SWI/SNF利用ATP水解产生的能量来产生超螺旋扭转、移动单核小体、增强核小体DNA的可及性，并从单核小体中去除H2A-H2B二聚体。在此，我们描述了一种仅由三个亚基Swi2p、Arp7p和Arp9p组成的SWI/SNF亚复合物的ATP依赖活性。虽然该亚复合物在大多数重塑试验中功能完全正常，但Swi2p-Arp7p-Arp9p在ATP依赖的H2A-H2B二聚体去除方面存在缺陷。我们将Swi3p亚基的酸性N端鉴定为ATP依赖的二聚体丢失所需的新型H2A-H2B结合结构域。我们的数据表明，H2A-H2B二聚体丢失不是ATP依赖的DNA易位的必然结果，此外，它们还表明SWI/SNF由至少四个相互依赖的模块组成。
