Aurora B controls the association of condensin I but not condensin II with mitotic chromosomes

Abstract

The assembly of mitotic chromosomes is controlled by condensin complexes. In vertebrates, condensin I binds to chromatin in prometaphase, confers rigidity to chromosomes and enables the release of cohesin complexes from chromosome arms, whereas condensin II associates with chromosomes in prophase and promotes their condensation. Both complexes are essential for chromosome segregation in anaphase. Although the association of condensins with chromatin is important for the assembly and segregation of mitotic chromosomes, it is poorly understood how this process is controlled. Here we show that the mitotic kinase Aurora B regulates the association of condensin I, but not the interaction of condensin II with chromatin. Quantitative time-lapse imaging of cells expressing GFP-tagged condensin subunits revealed that Aurora B is required for efficient loading of condensin I onto chromosomes in prometaphase and for maintenance of the complex on chromosomes in later stages of mitosis. The three non-SMC subunits of condensin I are Aurora B substrates in vitro and their mitosis-specific phosphorylation depends on Aurora B in vivo. Our data indicate that Aurora B contributes to chromosome rigidity and segregation by promoting the binding of condensin I to chromatin. We have also addressed how Aurora B might mediate the dissociation of cohesin from chromosome arms.

Specific primary sequence requirements for Aurora B kinase-mediated phosphorylation and subcellular localization of TMAP during mitosis

“…A number of (candidate) substrates of Aurora B have been identified so far. 4,8,[12][13][14][15][16][17][18][19] Based on the previously reported phosphorylation sites for Aurora B kinase, the following consensus phosphorylation motif has been proposed: (R/K) 1-3 -X-(S/T) or (R/K)-(R/K)-X 0-2 -(S/T) where X denotes any amino acid. 15,20 However, few studies provide evidence for phosphorylation of the substrates by Aurora B in vivo, and even fewer studies report on the identification of the Aurora B-specific phosphorylation residues.…”

“…2 The CPC controls various events during mitosis, including regulation of the mitotic chromosome, 3,4 spindle structure, 5,6 kinetochore-microtubule attachments, 7,8 spindle assembly checkpoint 9 and completion of cytokinesis. 10 It is thought that the diversity of the mitotic functions of the CPC reflects the highly dynamic nature of its subcellular localization during mitosis.…”

Shugoshin regulates cohesion by driving relocalization of PP2A in Xenopus extracts

“…In the case of Aurora B, Sgo appears not to be the only relevant target of the kinase in this prophase pathway. Other possible targets could be condensin, heterochromatin protein 1 (HP1), or some other protein yet to be identified (Fischle et al 2005;Hirota et al 2005;Lipp et al 2007). …”

Chromosome Dynamics during Mitosis

“…The molecular picture of how the localization and activities of condensin I might be regulated is far from complete, although numerous studies have identified involvement of multiple mitotic kinases, including Cdk1 (Kimura et al 1998;St-Pierre et al 2009), Aurora B (Lipp et al 2007;Collette et al 2011;Nakazawa et al 2011;Tada et al 2011), and Polo-like kinase (St-Pierre et al 2009). Sumoylation has also been implicated in the function of condensin in ribosomal DNA (rDNA) maintenance (Takahashi et al 2008) and kinetochore localization (BachellierBassi et al 2008) in budding yeast.…”