Recruitment of a SUMO isopeptidase to rDNA stabilizes silencing complexes by opposing SUMO targeted ubiquitin ligase activity.
Post-translational modification by SUMO (small ubiquitin-like modifier) plays important but still poorly understood regulatory roles in eukaryotic cells, including as a signal for ubiquitination by SUMO targeted ubiquitin ligases (STUbLs). Here, we delineate the molecular mechanisms for SUMO-dependent control of ribosomal DNA (rDNA) silencing through the opposing actions of a ... STUbL (Slx5:Slx8) and a SUMO isopeptidase (Ulp2). We identify a conserved region in the Ulp2 C terminus that mediates its specificity for rDNA-associated proteins and show that this region binds directly to the rDNA-associated protein Csm1. Two crystal structures show that Csm1 interacts with Ulp2 and one of its substrates, the rDNA silencing protein Tof2, through adjacent conserved interfaces in its C-terminal domain. Disrupting Csm1's interaction with either Ulp2 or Tof2 dramatically reduces rDNA silencing and causes a marked drop in Tof2 abundance, suggesting that Ulp2 promotes rDNA silencing by opposing STUbL-mediated degradation of silencing proteins. Tof2 abundance is rescued by deletion of the STUbLSLX5or disruption of its SUMO-interacting motifs, confirming that Tof2 is targeted for degradation in a SUMO- and STUbL-dependent manner. Overall, our results demonstrate how the opposing actions of a localized SUMO isopeptidase and a STUbL regulate rDNA silencing by controlling the abundance of a key rDNA silencing protein, Tof2.
Mesh Terms:
Amino Acid Motifs, Cell Cycle Proteins, Cell Nucleolus, Crystallization, DNA, Ribosomal, Endopeptidases, Gene Silencing, Intracellular Signaling Peptides and Proteins, Models, Molecular, Nuclear Proteins, Protein Binding, Protein Stability, Protein Structure, Quaternary, Proteolysis, Saccharomyces cerevisiae Proteins, Small Ubiquitin-Related Modifier Proteins, Sumoylation, Ubiquitin-Protein Ligases
Amino Acid Motifs, Cell Cycle Proteins, Cell Nucleolus, Crystallization, DNA, Ribosomal, Endopeptidases, Gene Silencing, Intracellular Signaling Peptides and Proteins, Models, Molecular, Nuclear Proteins, Protein Binding, Protein Stability, Protein Structure, Quaternary, Proteolysis, Saccharomyces cerevisiae Proteins, Small Ubiquitin-Related Modifier Proteins, Sumoylation, Ubiquitin-Protein Ligases
Genes Dev.
Date: Dec. 15, 2016
PubMed ID: 28487408
View in: Pubmed Google Scholar
Download Curated Data For This Publication
207265
Switch View:
- Interactions 71