Dataset Information

The FACT Spt16 "peptidase" domain is a histone H3-H4 binding module.

ABSTRACT: The FACT complex is a conserved cofactor for RNA polymerase II elongation through nucleosomes. FACT bears histone chaperone activity and contributes to chromatin integrity. However, the molecular mechanisms behind FACT function remain elusive. Here we report biochemical, structural, and mutational analyses that identify the peptidase homology domain of the Schizosaccharomyces pombe FACT large subunit Spt16 (Spt16-N) as a binding module for histones H3 and H4. The 2.1-A crystal structure of Spt16-N reveals an aminopeptidase P fold whose enzymatic activity has been lost. Instead, the highly conserved fold directly binds histones H3-H4 through a tight interaction with their globular core domains, as well as with their N-terminal tails. Mutations within a conserved surface pocket in Spt16-N or posttranslational modification of the histone H4 tail reduce interaction in vitro, whereas the globular domains of H3-H4 and the H3 tail bind distinct Spt16-N surfaces. Our analysis suggests that the N-terminal domain of Spt16 may add to the known H2A-H2B chaperone activity of FACT by including a H3-H4 tail and H3-H4 core binding function mediated by the N terminus of Spt16. We suggest that these interactions may aid FACT-mediated nucleosome reorganization events.

SUBMITTER: Stuwe T

PROVIDER: S-EPMC2449335 | biostudies-literature | 2008 Jul

REPOSITORIES: biostudies-literature

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The FACT Spt16 "peptidase" domain is a histone H3-H4 binding module.

Stuwe Tobias T Hothorn Michael M Lejeune Erwan E Rybin Vladimir V Bortfeld Miriam M Scheffzek Klaus K Ladurner Andreas G AG

Proceedings of the National Academy of Sciences of the United States of America 20080625 26

The FACT complex is a conserved cofactor for RNA polymerase II elongation through nucleosomes. FACT bears histone chaperone activity and contributes to chromatin integrity. However, the molecular mechanisms behind FACT function remain elusive. Here we report biochemical, structural, and mutational analyses that identify the peptidase homology domain of the Schizosaccharomyces pombe FACT large subunit Spt16 (Spt16-N) as a binding module for histones H3 and H4. The 2.1-A crystal structure of Spt16 ...[more]

PMID: 18579787

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Project description:BACKGROUND:NASP is an essential protein in mammals that functions in histone transport pathways and maintenance of a soluble reservoir of histones H3/H4. NASP has been studied exclusively in Opisthokonta lineages where some functional diversity has been reported. In humans, growing evidence implicates NASP miss-regulation in the development of a variety of cancers. Although a comprehensive phylogenetic analysis is lacking, NASP-family proteins that possess four TPR motifs are thought to be widely distributed across eukaryotes. RESULTS:We characterize the molecular evolution of NASP by systematically identifying putative NASP orthologs across diverse eukaryotic lineages ranging from excavata to those of the crown group. We detect extensive silent divergence at the nucleotide level suggesting the presence of strong purifying selection acting at the protein level. We also observe a selection bias for high frequencies of acidic residues which we hypothesize is a consequence of their critical function(s), further indicating the role of functional constraints operating on NASP evolution. Our data indicate that TPR1 and TPR4 constitute the most rapidly evolving functional units of NASP and may account for the functional diversity observed among well characterized family members. We also show that NASP paralogs in ray-finned fish have different genomic environments with clear differences in their GC content and have undergone significant changes at the protein level suggesting functional diversification. CONCLUSION:We draw four main conclusions from this study. First, wide distribution of NASP throughout eukaryotes suggests that it was likely present in the last eukaryotic common ancestor (LECA) possibly as an important innovation in the transport of H3/H4. Second, strong purifying selection operating at the protein level has influenced the nucleotide composition of NASP genes. Further, we show that selection has acted to maintain a high frequency of functionally relevant acidic amino acids in the region that interrupts TPR2. Third, functional diversity reported among several well characterized NASP family members can be explained in terms of quickly evolving TPR1 and TPR4 motifs. Fourth, NASP fish specific paralogs have significantly diverged at the protein level with NASP2 acquiring a NNR domain.

Dataset Information

The FACT Spt16 "peptidase" domain is a histone H3-H4 binding module.

Publications

The FACT Spt16 "peptidase" domain is a histone H3-H4 binding module.

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