Cell-Cycle Regulation of Dynamic ChromosomeAssociation of the Condensin Complex

Eukaryotic cells inherit their genomes in the form ofchromosomes, which are formed from the compac-tion of interphase chromatin by the condensin com-plex. Condensin is a member of the structural main-tenance of chromosomes (SMC) family of ATPases,large ring-shaped protein assemblies that entrapDNA to establish chromosomal interactions. Here,we use the budding yeastSaccharomyces cerevisiaeto dissect the role of the condensin ATPase and itsrelationship with cell-cycle-regulated chromosomebinding dynamics. ATP hydrolysis-deficient conden-sin binds to chromosomes but is defective in chro-mosome condensation and segregation. By modu-lating the ATPase, we demonstrate that it controlscondensin’s dynamic turnover on chromosomes.Mitosis-specific phosphorylation of condensin’sSmc4 subunit reduces the turnover rate. However,reducing turnover by itself is insufficient to compactchromosomes. We propose that condensation re-quires fine-tuned dynamic condensin interactionswith more than one DNA. These results enhanceour molecular understanding of condensin functionduring chromosome condensation