The Sir4 H-BRCT domain interacts with phospho-proteins to sequester and repress yeast heterochromatin

EMBO J. 2019 Oct 15;38(20):e101744. doi: 10.15252/embj.2019101744. Epub 2019 Sep 12.

Abstract

In Saccharomyces cerevisiae, the silent information regulator (SIR) proteins Sir2/3/4 form a complex that suppresses transcription in subtelomeric regions and at the homothallic mating-type (HM) loci. Here, we identify a non-canonical BRCA1 C-terminal domain (H-BRCT) in Sir4, which is responsible for tethering telomeres to the nuclear periphery. We show that Sir4 H-BRCT and the closely related Dbf4 H-BRCT serve as selective phospho-epitope recognition domains that bind to a variety of phosphorylated target peptides. We present detailed structural information about the binding mode of established Sir4 interactors (Esc1, Ty5, Ubp10) and identify several novel interactors of Sir4 H-BRCT, including the E3 ubiquitin ligase Tom1. Based on these findings, we propose a phospho-peptide consensus motif for interaction with Sir4 H-BRCT and Dbf4 H-BRCT. Ablation of the Sir4 H-BRCT phospho-peptide interaction disrupts SIR-mediated repression and perinuclear localization. In conclusion, the Sir4 H-BRCT domain serves as a hub for recruitment of phosphorylated target proteins to heterochromatin to properly regulate silencing and nuclear order.

Keywords: Dbf4; SIR complex; Sir4 BRCT domain; Tom1; heterochromatin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Gene Expression Regulation, Fungal
  • Gene Silencing*
  • Heterochromatin / genetics
  • Heterochromatin / metabolism*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism
  • Protein Conformation
  • Protein Domains
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Sequence Homology
  • Silent Information Regulator Proteins, Saccharomyces cerevisiae / chemistry
  • Silent Information Regulator Proteins, Saccharomyces cerevisiae / genetics
  • Silent Information Regulator Proteins, Saccharomyces cerevisiae / metabolism*
  • Telomere
  • Ubiquitin Thiolesterase / genetics
  • Ubiquitin Thiolesterase / metabolism*
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*

Substances

  • Esc1 protein, S cerevisiae
  • Heterochromatin
  • Nuclear Proteins
  • Phosphoproteins
  • SIR4 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Silent Information Regulator Proteins, Saccharomyces cerevisiae
  • TOM1 protein, S cerevisiae
  • Ubiquitin-Protein Ligases
  • UBP10 protein, S cerevisiae
  • Ubiquitin Thiolesterase

Associated data

  • PDB/6RRV
  • PDB/6QSZ
  • PDB/6QTM
  • PDB/6RR0