BIOLOGY 2B03 Lecture Notes - Lecture 10: Spindle Apparatus, Histone H3, Histone H1
23 Apr 2020
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Module 10 lecture 1: cell cycle dynamics and checkpoints: targets of mpf. Chromosome condensation: highly compact chromosomes in have centromeres that are closely attached by cohesion complexes while arms have separated apart from on another slightly, targets of mpf, condensins, cohesins, histones, h1 and h3, topoisomerase. Histones: many proteins for chromosome condensation and phosphorylation is key regulatory switch in each case, dna organized around chromosomal binding proteins called histones. Cohesins: 2 other protein families important to mitotic chromosome organization - cohesins and condensins, cohesin proteins form cohesin complex - required to hold sister chromatids together after replication release of cohesins = 2 steps: 1) bulk release of cohesins from chromosome arms while maintaining cohesins at centromere this produces the x-shaped chromosome we always see. Chromosome decondensation: condensins and histones phosphorylated in mitosis are now dephosphorylated, occurs with inactivation of cyclinb/cdk, activity of phosphatases reverses protein phosphorylation and removes condensins and remodelling of dna around histones to direct chromosome decondensation.
