Abstract
SummaryEukaryotic cells inherit their genomes in the form of chromosomes, which are formed from the compaction of interphase chromatin by the condensin complex. Condensin is a member of the structural maintenance of chromosomes (SMC) family of ATPases, large ring-shaped protein assemblies that entrap DNA to establish chromosomal interactions. Here, we use the budding yeast Saccharomyces cerevisiae to dissect the role of the condensin ATPase and its relationship with cell-cycle-regulated chromosome binding dynamics. ATP hydrolysis-deficient condensin binds to chromosomes but is defective in chromosome condensation and segregation. By modulating the ATPase, we demonstrate that it controls condensin’s dynamic turnover on chromosomes. Mitosis-specific phosphorylation of condensin’s Smc4 subunit reduces the turnover rate. However, reducing turnover by itself is insufficient to compact chromosomes. We propose that condensation requires fine-tuned dynamic condensin interactions with more than one DNA. These results enhance our molecular understanding of condensin function during chromosome condensation.
Highlights
The condensin complex is a key structural component of mitotic chromosomes (Hirano, 2016; Uhlmann, 2016). It consists of two structural maintenance of chromosomes (SMC) subunits, Smc2 and Smc4, that constitute the circumference of the condensin ring
The Condensin ATPase Is Essential for Yeast Cell Proliferation To study the condensin ATPase, we generated a series of mutations in conserved residues of budding yeast Smc2 and Smc4 that were designed to disrupt aspects of the ATPase cycle, based on previous studies of SMC ATPases (Arumugam et al, 2003; Hopfner et al, 2000; Lammens et al, 2004; Lengronne et al, 2006; Weitzer et al, 2003)
To extend the analysis to nonrDNA loci and to repeat it using a complementary technique, we examined the chromosomal binding of Smc4 ATPase mutants by chromatin immunoprecipitation, followed by qPCR
Summary
The condensin complex is a key structural component of mitotic chromosomes (Hirano, 2016; Uhlmann, 2016). It consists of two structural maintenance of chromosomes (SMC) subunits, Smc and Smc, that constitute the circumference of the condensin ring. They dimerize via a hinge domain on one side of the ring and, on the other side, at a pair of ATPase head domains that form the catalytic core of the complex. ATP hydrolysis by condensin promotes DNA supercoiling, but how this relates to chromosome condensation is not yet understood (Kimura and Hirano, 1997). How dynamic chromosome binding is linked to condensin’s ATPase activity and how cell-cycle-dependent condensin modifications regulate this dynamic binding cycle are incompletely understood
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