In Vivo Mapping of FACT-Histone Interactions Identifies a Role of Pob3 C-terminus in H2A-H2B Binding

ACS Chem Biol. 2015 Dec 18;10(12):2753-63. doi: 10.1021/acschembio.5b00493. Epub 2015 Oct 5.

Abstract

Histone chaperones assist nucleosomal rearrangements to facilitate the passage of DNA and RNA polymerases through chromatin. The FACT (facilitates chromatin transcription) complex is a conserved histone chaperone involved in transcription, replication, and repair. The complex consists of two major subunits, Spt16 and SSRP1/Pob3 in mammals and yeast, which engage histones and DNA by multiple contacts. However, the precise mechanism of FACT function is largely unclear. Here, we used the genetically installed UV-activatable cross-linker amino acid p-benzoylphenylalanine (pBPA) to map the interaction network of FACT in living yeast. Unexpectedly, we found the acidic C-terminus of Pob3 forming cross-links to histone H2A and H2B most efficiently. This observation was independent of the performed cross-linking chemistry since similar histone cross-links were obtained using p-azidophenylalanine (pAzF). Further analyses identified a C-terminal nuclear localization sequence in Pob3. Its interaction with Importin-α interfered with H2A-H2B binding, which suggests a possible regulatory role in FACT recruitment to chromatin. Deletion of acidic residues from the Pob3 C-terminus creates a hydroxyurea-sensitive phenotype in budding yeast, suggesting a potential role for this domain in DNA replication.

MeSH terms

  • Carrier Proteins / chemistry
  • Carrier Proteins / metabolism
  • Chromatin / chemistry
  • Chromatin / metabolism*
  • Chromatin Assembly and Disassembly
  • Cross-Linking Reagents / chemistry
  • Histones / chemistry
  • Histones / metabolism*
  • Models, Biological
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Schizosaccharomyces pombe Proteins / chemistry
  • Schizosaccharomyces pombe Proteins / metabolism
  • Transcription Factors / chemistry
  • Transcription Factors / metabolism*

Substances

  • Carrier Proteins
  • Chromatin
  • Cross-Linking Reagents
  • Histones
  • POB3 protein, S cerevisiae
  • POB3 protein, S pombe
  • Saccharomyces cerevisiae Proteins
  • Schizosaccharomyces pombe Proteins
  • Transcription Factors