Functional roles of the DNA-binding HMGB domain in the histone chaperone FACT in nucleosome reorganization.

Autor:	McCullough LL; From the Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84132., Connell Z; From the Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84132., Xin H; From the Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84132., Studitsky VM; the Biology Faculty, Lomonosov, Moscow State University, Leninskie Gory 1, Moscow 119992, Russia.; the Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111., Feofanov AV; the Biology Faculty, Lomonosov, Moscow State University, Leninskie Gory 1, Moscow 119992, Russia.; the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117997, Russia, and., Valieva ME; the Biology Faculty, Lomonosov, Moscow State University, Leninskie Gory 1, Moscow 119992, Russia., Formosa T; From the Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84132, tim@biochem.utah.edu.
Jazyk:	angličtina
Zdroj:	The Journal of biological chemistry [J Biol Chem] 2018 Apr 20; Vol. 293 (16), pp. 6121-6133. Date of Electronic Publication: 2018 Mar 07.
DOI:	10.1074/jbc.RA117.000199
Abstrakt:	The essential histone chaperone FACT ( fa cilitates c hromatin t ranscription) promotes both nucleosome assembly and disassembly. FACT is a heterodimer of Spt16 with either SSRP1 or Pob3, differing primarily by the presence of a high-mobility group B (HMGB) DNA-binding domain furnished only by SSRP1. Yeast FACT lacks the intrinsic HMGB domain found in SSRP1-based homologs such as human FACT, but yeast FACT activity is supported by Nhp6, which is a freestanding, single HMGB-domain protein. The importance of histone binding by FACT domains has been established, but the roles of DNA-binding activity remain poorly understood. Here, we examined these roles by fusing single or multiple HMGB modules to Pob3 to mimic SSRP1 or to test the effects of extended DNA-binding capacity. Human FACT and a yeast mimic both required Nhp6 to support nucleosome reorganization in vitro , indicating that a single intrinsic DNA-binding HMGB module is insufficient for full FACT activity. Three fused HMGB modules supported activity without Nhp6 assistance, but this FACT variant did not efficiently release from nucleosomes and was toxic in vivo Notably, intrinsic DNA-binding HMGB modules reduced the DNA accessibility and histone H2A-H2B dimer loss normally associated with nucleosome reorganization. We propose that DNA bending by HMGB domains promotes nucleosome destabilization and reorganization by exposing FACT's histone-binding sites, but DNA bending also produces DNA curvature needed to accommodate nucleosome assembly. Intrinsic DNA-bending activity therefore favors nucleosome assembly by FACT over nucleosome reorganization, but excessive activity impairs FACT release, suggesting a quality control checkpoint during nucleosome assembly. (© 2018 by The American Society for Biochemistry and Molecular Biology, Inc.)
Databáze:	MEDLINE
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