Timely removal of DNA recombination intermediates is critical for genome stability. The DNA helicase-topoisomerase complex, Sgs1-Top3-Rmi1 (STR), is the major pathway for processing these ...intermediates to generate conservative products. However, the mechanisms that promote STR-mediated functions remain to be defined. Here we show that Sgs1 binds to poly-SUMO chains and associates with the Smc5/6 SUMO E3 complex in yeast. Moreover, these interactions contribute to the sumoylation of Sgs1, Top3, and Rmi1 upon the generation of recombination structures. We show that reduced STR sumoylation leads to accumulation of recombination structures, and impaired growth in conditions when these structures arise frequently, highlighting the importance of STR sumoylation. Mechanistically, sumoylation promotes STR inter-subunit interactions and accumulation at DNA repair centers. These findings expand the roles of sumoylation and Smc5/6 in genome maintenance by demonstrating that they foster STR functions in the removal of recombination intermediates.
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•Sgs1 interacts with the Smc5/6 SUMO ligase complex•Smc5/6 promotes STR sumoylation upon recombination intermediate formation•STR sumoylation aids recombination intermediate removal•Sumoylation favors STR inter-subunit interactions and accumulation at DNA repair foci
Bonner et al. show that the Smc5/6 SUMO ligase complex interacts with and promotes the sumoylation of the DNA helicase Sgs1 and its partner proteins Top3 and Rmi1. Sgs1-Top3-Rmi1 (STR) sumoylation fosters the removal of recombination intermediates, in part by stimulating STR inter-subunit interaction and STR accumulation at DNA repair centers.
Molecular chaperones triage misfolded proteins via action as substrate selectors for quality control (QC) machines that fold or degrade clients. Herein, the endoplasmic reticulum (ER)-associated ...Hsp40 JB12 is reported to participate in partitioning mutant conformers of gonadotropin-releasing hormone receptor (GnRHR), a G protein-coupled receptor, between ER-associated degradation (ERAD) and an ERQC autophagy pathway. ERQC autophagy degrades E90K-GnRHR because pools of its partially folded and detergent-soluble degradation intermediates are resistant to ERAD. S168R-GnRHR is globally misfolded and disposed of via ERAD, but inhibition of p97, the protein retrotranslocation motor, shunts S168R-GnRHR from ERAD to ERQC autophagy. Partially folded and grossly misfolded forms of GnRHR associate with JB12 and Hsp70. Elevation of JB12 promotes ERAD of S168R-GnRHR, with E90K-GnRHR being resistant. E90K-GnRHR elicits association of the Vps34 autophagy initiation complex with JB12. Interaction between ER-associated Hsp40s and the Vps34 complex permits the selective degradation of ERAD-resistant membrane proteins via ERQC autophagy.
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•A route for ERQC autophagy of soluble ERAD-resistant GnRHR mutants is discovered•Partitioning of E90K-GnRHR between ERAD and ERQC autophagy is conformation dependent•ERQC autophagy initiates via E90K-GnRHR-driven association of Vps34 with DNAJB12•Rates of GnRHR degradation via ERAD or ERQC autophagy are similar
The cell utilizes a variety of quality control systems to degrade terminally misfolded proteins. Here, Houck et al. discover an ER quality control autophagy pathway for degradation of mutants of the transmembrane protein GnRHR, in which not the aggregation status, but the conformation, determines partitioning of misfolded GnRHR between ERAD and ERQC autophagy.
Budding yeast Mph1 helicase and its orthologs drive multiple DNA transactions. Elucidating the mechanisms that regulate these motor proteins is central to understanding genome maintenance processes. ...Here, we show that the conserved histone fold MHF complex promotes Mph1-mediated repair of damaged replication forks but does not influence the outcome of DNA double-strand break repair. Mechanistically, scMHF relieves the inhibition imposed by the structural maintenance of chromosome protein Smc5 on Mph1 activities relevant to replication-associated repair through binding to Mph1 but not DNA. Thus, scMHF is a function-specific enhancer of Mph1 that enables flexible response to different genome repair situations.
Recombinational repair processes multiple types of DNA lesions. Though best understood in the repair of DNA breaks, recombinational repair is intimately linked to other situations encountered during ...replication. As DNA strands are decorated with many types of blocks that impede the replication machinery, a great number of genomic regions cannot be duplicated without the help of recombinational repair. This replication-associated recombinational repair employs both the core recombination proteins used for DNA break repair and the specialized factors that couple replication with repair. Studies from multiple organisms have provided insights into the roles of these specialized factors, with the findings in budding yeast being advanced through use of powerful genetics and methods for detecting DNA replication and repair intermediates. In this review, we summarize recent progress made in this organism, ranging from our understanding of the classical template switch mechanisms to gap filling and replication fork regression pathways. As many of the protein factors and biological principles uncovered in budding yeast are conserved in higher eukaryotes, these findings are crucial for stimulating studies in more complex organisms.
We identified Mte1 (Mph1-associated telomere maintenance protein 1) as a multifunctional regulator of Saccharomyces cerevisiae Mph1, a member of the FANCM family of DNA motor proteins important for ...DNA replication fork repair and crossover suppression during homologous recombination. We show that Mte1 interacts with Mph1 and DNA species that resemble a DNA replication fork and the D loop formed during recombination. Biochemically, Mte1 stimulates Mph1-mediated DNA replication fork regression and branch migration in a model substrate. Consistent with this activity, genetic analysis reveals that Mte1 functions with Mph1 and the associated MHF complex in replication fork repair. Surprisingly, Mte1 antagonizes the D-loop-dissociative activity of Mph1-MHF and exerts a procrossover role in mitotic recombination. We further show that the influence of Mte1 on Mph1 activities requires its binding to Mph1 and DNA. Thus, Mte1 differentially regulates Mph1 activities to achieve distinct outcomes in recombination and replication fork repair.
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