The Sir4 H-BRCT domain interacts with phospho-proteins to sequester and repress yeast heterochromatin.Deshpande, I., Keusch, J.J., Challa, K., Iesmantavicius, V., Gasser, S.M., Gut, H.
(2019) EMBO J 38: e101744-e101744
- PubMed: 31515872
- DOI: https://doi.org/10.15252/embj.2019101744
- Primary Citation of Related Structures:
6QSZ, 6QTM, 6RR0, 6RRV
- PubMed 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.
Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland.