Abstract
ABSTRACTThe Smc5/6 complex in Saccharomyces cerevisiae contains six essential non-Smc elements, Nse1-6. With the exception of Nse2 (also known as Mms21), which is an E3 small ubiquitin-like modifier (SUMO) ligase, very little is understood about the role of these components or their contribution to Smc5/6 functionality. Our characterization of Nse5 establishes a previously unidentified relationship between the Smc5/6 complex and factors of the SUMO pathway. Nse5 physically associates with the E2 conjugating enzyme, Ubc9, where contacts are stabilized by non-covalent interactions with SUMO. SUMO also mediates the interactions between Nse5 and the two PIAS family E3 SUMO ligases, Siz1 and Siz2. Cells carrying the nse5-ts1 allele or lacking either SIZ1 or SIZ2 exhibit a reduction in Smc5 sumoylation upon MMS treatment and demonstrate functional redundancy for SUMO mediated events in the presence of DNA damage. Overall, given the extensive connection between Nse5 and components of the SUMO pathway, we speculate that one function of the Smc5/6 complex might be as a scaffold center to enable sumoylation events in budding yeast.
Highlights
The Smc5/6 complex is a member of the structural maintenance of chromosomes (SMC) family of proteins that includes cohesin and condensin
Genetic interactions and Smc5 sumoylation in nse5-ts1 mutants during methyl methane sulfonate (MMS) treatment The Smc5/6 complex is involved in DNA replication and repair and characterizing the individual subcomponents of the complex will augment full understanding of how Smc5/6 works
As Mms21 is small ubiquitin-like modifier (SUMO) ligase (Zhao and Blobel, 2005) and Nse5 has potential ties to the SUMO pathway (Hazbun et al, 2003; Bustard et al, 2012), we wanted to investigate if Nse5 mediates the sumoylation of certain target proteins, such as Smc5, after MMS exposure
Summary
The Smc5/6 complex is a member of the structural maintenance of chromosomes (SMC) family of proteins that includes cohesin and condensin. These complexes function in part by providing organization to chromatin during multiple processes including transcription, chromosome condensation and segregation, and DNA repair (Jeppsson et al, 2014; Tapia-Alveal et al, 2014). In Schizosaccharomyces pombe (fission yeast), Nse and Nse were mapped to bind the head region of Smc and Smc
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