Roles for Condensin in C. elegans Chromosome Dynamics.

[摘要] Condensin complexes are essential for higher order organization of chromosomestructure. Higher eukaryotes have two condensins (condensin I and II) dedicated tomitotic and meiotic chromosome dynamics. C. elegans was thought to be an anomaly,with only a single mitotic condensin (condensin II), and one specialized for dosagecompensation (condensin IDC). Condensin IDC binds both hermaphrodite X chromosomes to reduce gene expression by half, equalizing X-linked geneproduct in males (XO) and hermaphrodites (XX), while condensin II is essential forefficient chromosome organization and segregation during mitosis and meiosis. It wasproposed that the unusual holocentric chromosomes in C. elegans did not requirecondensin I and II to accomplish cell division, and therefore, condensin I was customizedfor X chromosome regulation. However, we showed that subunits from condensin IDC andcondensin II interact to form a second mitotic/meiotic condensin, the bonafide C. eleganscondensin I. Our findings raise C. elegans to a unique status, with three distinctcondensins controlling holocentric chromosome dynamics.Condensin I and II have distinct localization patterns on mitotic and meioticchromosomes, suggesting that their roles in chromosome organization may be distinct.During mitosis, condensin II colocalizes with the centromere while condensin Idiscontinuously coats chromosomes. Condensin I, but not II, colocalizes with aurora Bkinase, AIR-2, and our data suggests that in mitosis, AIR-2 activity is required for therecruitment of condensin I, but not condensin II. In meiosis, condensin II localizes to thesister chromatid core, while condensin I localizes to the interface between homologouschromosomes. Condensin I and AIR-2 colocalize at this interface. Similar to mitosis, inAIR-2 depleted animals undergoing meiosis, condensin II is not affected but condensin Imislocalizes to the interface between sister chromatids, as well as homologous chromosomes. This work indicates that AIR-2 provides important spatial cues for condensin I localization on meiotic chromosomes.The contribution of condensin I to during mitosis and meiosis is not well-defined. Acomparative analysis of chromosome organization and mitotic/ meiotic progressionbetween wildtype and condensin I depleted animals will provide a better understandingof condensin I function in chromosome dynamics during cell division.

[发布机构] University of Michigan

[效力级别] Molecular

[关键词] Condensin Complexes in C. Elegans;Molecular;Cellular and Developmental Biology;Science;Molecular, Cellular, and Developmental Biology