A Diagram of the organization of the kinetochore. Cell Cycle 9 : — Polo-like kinase Cdc5 promotes chiasmata formation and cosegregation of sister centromeres at meiosis I. In the indirect regulation, the pulling apart of sister centromeres removes kinetochores from the field of action of the kinase Aurora B, which continuously phosphorylates kinetochore components within its reach to disrupt kinetochore—microtubule attachments Biggins et al.
Whether these are the only critical functions that these kinases play in mono-orientation is not yet known. Indeed, microtubule flux may be particularly important in meiosis to support chromosome motion.
Meiosis-specific DNA double-strand breaks are catalyzed by Spo11, a member of a widely conserved protein family. Lateral attachments are subsequently converted into the stronger and more processive end-on attachments. Molecular architecture of a kinetochore—microtubule attachment site.
Rec8 phosphorylation and recombination promote the step-wise loss of cohesins in meiosis. Nat Cell Biol 6 : — Microtubule polymerization dynamics.
In these acentrosomal divisions, the spindle is assembled from the self-organization of many alternative microtubule-organizing centers Schuh and Ellenbergoften including chromatin itself Heald et al. The Drosophila mei-S gene promotes sister-chromatid cohesion in meiosis following kinetochore differentiation.
The alternate, conformational wave model postulates that as the microtubule protofilaments bend outward during depolymerization, they push on the kinetochore, pulling it along the microtubule Koshland et al. Indeed, the recombinant Ndc80 complex favors rescue the transition from microtubule shortening to growth by directly stabilizing the tips of disassembling microtubules Akiyoshi et al.
Annu Rev Genet 47 : — Other unusual features of meiosis in some organisms Sister kinetochore mono-orientation in holocentric chromosomes So far, our discussion has been focused on chromosomes where the kinetochore assembles on a single locus; these are called monocentric chromosomes because they have one centromere.
Kinetochores bind strongly to growing microtubules and weakly to shrinking microtubules.