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Publication Abstract from PubMed

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.

The Sir4 H-BRCT domain interacts with phospho-proteins to sequester and repress yeast heterochromatin.,Deshpande I, Keusch JJ, Challa K, Iesmantavicius V, Gasser SM, Gut H EMBO J. 2019 Oct 15;38(20):e101744. doi: 10.15252/embj.2019101744. Epub 2019 Sep , 12. PMID:31515872^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.