Interphase cohesin regulation ensures mitotic fidelity after genome Biology Diagrams Preparations for mitotic chromosome segregation begin in the S phase of the cell cycle, as each chromosome is copied to generate two identical sister chromatids and cohesion is established between While one of the primary roles for chromosome cohesion in bi-orientation and mitotic chromosome segregation is well-established, the complexities of the regulation of cohesion are still being discovered. Segregation of chromosomes in mitosis is preceded by chromosome reorganization into the characteristic mitotic shapes observed in most animal cells. This chromosome reorganization takes place during early mitosis (prophase and prometaphase) and involves two major structural changes. First, sister chromatids are resolved from each other while both sister chromatid cohesion and DNA catenation
Cohesin is a ring-shaped protein complex that organises the genome, enabling its condensation, expression, repair and transmission. In this Primer, Makrantoni and Marston summarise the molecular functions and regulation of cohesin that underlie its central role in chromosome segregation during mitosis. During mitosis and meiosis sister chromatids are held together by protein complexes. This cohesion is important not only for pairwise alignment of chromosomes on the mitotic spindle but also for the generation of tension across centromeres - it counteracts the pulling force of spindle microtubules, which ensures the bipolar attachment of chromosomes. Chromosome cohesion thus enables accurate
Cohesin and chromosome segregation: Current Biology Biology Diagrams
The key difference between meiosis and mitosis is that meiotic cells undergo two cell divisions, meiosis I and meiosis II, without an intervening S phase. During meiosis I, the chromatin condenses as in mitosis and the sister chromatids are held together through a process called cohesion. Proper mitotic chromosome structure is essential for faithful chromosome segregation. Mounting evidence suggests that mitotic chromosome assembly is a progressive, dynamic process that requires topoisomerase II, condensins and cohesin and the activity of several signalling molecules. Current results suggest how these different activities might interact to achieve the familiar form of the In mitosis, cohesin maintains sister chromatid cohesion mainly at centromeres, while most cohesin is removed from chromosome arms until metaphase (meta). Condensins I and II are recruited to the chromatid axes and participate to construct mitotic chromosomes.
Many of the proteins that regulate cohesin function during mitosis also appear to regulate cohesin during meiosis. Here we review how cohesin contributes to meiotic chromosome dynamics, and explore similarities and differences between cohesin regulation during the mitotic cell cycle and meiotic progression.
