title: Structure-function studies of histone H3/H4 tetramer maintenance during transcription by chaperone Spt2.
abstract: Cells use specific mechanisms such as histone chaperones to abrogate the inherent barrier that the nucleosome poses to transcribing polymerases. The current model postulates that nucleosomes can be transiently disrupted to accommodate passage of RNA polymerases and that histones H3 and H4 possess their own chaperones dedicated to the recovery of nucleosomes. Here, we determined the crystal structure of the conserved C terminus of human Suppressors of Ty insertions 2 (hSpt2C) chaperone bound to an H3/H4 tetramer. The structural studies demonstrate that hSpt2C is bound to the periphery of the H3/H4 tetramer, mimicking the trajectory of nucleosomal-bound DNA. These structural studies have been complemented with in vitro binding and in vivo functional studies on mutants that disrupt key intermolecular contacts involving two acidic patches and hydrophobic residues on Spt2C. We show that contacts between both human and yeast Spt2C with the H3/H4 tetramer are required for the suppression of H3/H4 exchange as measured by H3K56ac and new H3 deposition. These interactions are also crucial for the inhibition of spurious transcription from within coding regions. Together, our data indicate that Spt2 interacts with the periphery of the H3/H4 tetramer and promotes its recycling in the wake of RNA polymerase.
authors.affiliation: Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA;
authors.forename: Shoudeng
authors.initials: S
authors.lastname: Chen
authors.affiliation: Groupe St-Patrick de Recherche en Oncologie Fondamentale, L'Hôtel-Dieu de Québec (Université Laval), Québec G1R 2J6, Canada;
authors.forename: Anne
authors.initials: A
authors.lastname: Rufiange
authors.affiliation: Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA;
authors.forename: Hongda
authors.initials: H
authors.lastname: Huang
authors.affiliation: Northeastern Collaborative Access Team (NE-CAT), Advanced Photon Source, Argonne National Laboratory, Chicago, Illinois 60439, USA; Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Kanagalaghatta R
authors.initials: KR
authors.lastname: Rajashankar
authors.affiliation: Groupe St-Patrick de Recherche en Oncologie Fondamentale, L'Hôtel-Dieu de Québec (Université Laval), Québec G1R 2J6, Canada;
authors.forename: Amine
authors.initials: A
authors.lastname: Nourani
authors.affiliation: Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA;
authors.forename: Dinshaw J
authors.initials: DJ
authors.lastname: Patel
mesh_terms: D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D005786:Gene Expression Regulation; D056488:Histone Chaperones / Q000378:metabolism*; D006657:Histones / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D046912:Multiprotein Complexes; D009707:Nucleosomes / Q000378:metabolism; D011485:Protein Binding; D055550:Protein Stability; D020836:Protein Structure, Quaternary; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D012492:Salts / Q000737:chemistry; D013329:Structure-Activity Relationship; D014158:Transcription, Genetic
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D056488:Histone Chaperones; D006657:Histones; D046912:Multiprotein Complexes; D009707:Nucleosomes; C585049:SPTY2D1 protein, human; D029701:Saccharomyces cerevisiae Proteins; D012492:Salts; C069938:SPT2 protein, S cerevisiae
keywords: H3/H4 tetramer; Spt2; epigenetics; histone chaperone; histone maintenance; spurious transcription; transcription elongation