Condensin I Stabilizes Chromosomes Mechanically through a Dynamic Interaction in Live Cells

Abstract

We conclude that while condensin I seems dispensable for normal chromosome compaction, its dynamic binding after nuclear envelope breakdown locks already condensed chromatin in a rigid state required for mechanically stable spindle attachment.

Condensin Regulates the Stiffness of Vertebrate Centromeres

“…However, those normally compacted centromeres lacking condensin respond abnormally to MT pulling forces. These findings confirm and extend a previous study in HeLa cells in which a MT-dependent abnormal mobility of kinetochores in metaphase was observed after condensin I RNAi (Gerlich et al, 2006). …”

“…Condensin is important for the architecture of mitotic chromosome arms (Coelho et al, 2003;Hudson et al, 2003;Hirota et al, 2004;Hirano, 2006), but it also localizes to centromeres (Saitoh et al, 1994;Gerlich et al, 2006), where condensin I, but not condensin II was reported to have a role in stabilizing the structure (Gerlich et al, 2006). It has recently been suggested that condensin could have a role in regulating the elastic behavior of centromeric chromatin.…”

“…Centromere and kinetochore tension and stretch are important for maintaining chromosome alignment (McIntosh et al, 2002), stabilizing kinetochore microtubule (kMT) attachments (Nicklas and Koch, 1969), spindle checkpoint signaling (Musacchio and Salmon, 2007;McEwen and Dong, 2009), and also for the back-to-back orientation of sister kinetochores (Loncarek et al, 2007). At least three independent factors have roles in the establishment of centromeric tension in metaphase: sister chromatid cohesion (Yeh et al, 2008), the elastic properties of chromatin (Houchmandzadeh et al, 1997;Almagro et al, 2004;Marko, 2008), and the higher order structure of the centromeric chromatin.Condensin is important for the architecture of mitotic chromosome arms (Coelho et al, 2003;Hudson et al, 2003;Hirota et al, 2004;Hirano, 2006), but it also localizes to centromeres (Saitoh et al, 1994;Gerlich et al, 2006), where condensin I, but not condensin II was reported to have a role in stabilizing the structure (Gerlich et al, 2006). It has recently been suggested that condensin could have a role in regulating the elastic behavior of centromeric chromatin.…”

“…One study found that condensin I-depleted Drosophila chromosomes were unable to align at a metaphase plate, had distorted kinetochore structures, and lost elasticity of their centromeric chromatin (Oliveira et al, 2005). However a similar study in human cells reported that although loss of condensin I caused kinetochores to undergo abnormal movements, these movements were bidirectional (e.g., reversible; Gerlich et al, 2006).Even after the publication of those results, the regulation and functional significance of centromere stretch remained unknown. An elegant study in budding yeast went on to find that chromatin structure sets the rest length of the centromere, but does not regulate its stretch (Bouck and Bloom, 2007).…”

Cell cycle control of spindle elongation

“…[10][11][12][13] Finally, as discussed below, a significant assistance to chromosome segregation in higher eukaryotes comes from condensation and compaction of mitotic chromosomes. [14][15][16][17] …”