Sister kinetochores are mechanically fused during meiosis I in yeast

Abstract

Production of healthy gametes requires a reductional meiosis I division in which replicated sister chromatids co-migrate, rather than separating as in mitosis or meiosis II. Fusion of sister kinetochores during meiosis I may underlie sister chromatid co-migration in diverse organisms, but direct evidence for such fusion has been lacking. Here we studied native kinetochore particles isolated from yeast using laser trapping and quantitative fluorescence microscopy. Meiosis I kinetochores formed stronger attachments and carried more microtubule-binding elements than kinetochores isolated from cells in mitosis or meiosis II. The meiosis I-specific monopolin complex was both necessary and sufficient to drive these modifications. Thus, kinetochore fusion directs sister chromatid co-migration, a conserved feature of meiosis that is fundamental to Mendelian inheritance.

Hierarchical Regulation of Centromeric Cohesion Protection by Meikin and Shugoshin during Meiosis I

“…Budding yeast Spo13 (sporulation-specific protein 13), another factor that is required for mono-orientation as well as cohesion protection, associates with the Polo-like kinase Cdc5 and acts to recruit or stabilize the monopolin complex at centromeres (Clyne et al 2003;Katis et al 2004Katis et al , 2010Lee et al 2004;Monje-Casas et al 2007). In budding yeast, paired sister centromeres assemble a single kinetochore and bind only one microtubule (Sarangapani et al 2014). Therefore, monopolin would conjoin two microtubule attachment sites and thereby make them into a one "point centromere.…”

From equator to pole: splitting chromosomes in mitosis and meiosis

“…4B; Sarkar et al 2013;Sarangapani et al 2014). Notably, this could also act as the point at which sister kinetochores are cross-linked into a single functional unit.…”

“…Kinetochores purified from meiosis I withstand more force and have more microtubule-binding elements than mitotic kinetochores (Sarangapani et al 2014). This is unlikely to be solely due to monopolininduced rearrangements in the architecture of individual kinetochores: DNA replication and thus the presence of a sister kinetochore are required for this increase in strength (Sarangapani et al 2014). Importantly, monopolin was able to increase the strength of mitotic kinetochores in vitro in a manner that was independent of casein kinase activity (Sarangapani et al 2014).…”

“…This is unlikely to be solely due to monopolininduced rearrangements in the architecture of individual kinetochores: DNA replication and thus the presence of a sister kinetochore are required for this increase in strength (Sarangapani et al 2014). Importantly, monopolin was able to increase the strength of mitotic kinetochores in vitro in a manner that was independent of casein kinase activity (Sarangapani et al 2014). The latter highlights our lack of understanding of the role of casein kinase in promoting mono-orientation.…”

Anaphase A: Melting Microtubules Move Chromosomes toward Spindle Poles

“…Reconstituted tip-couplers made from various combinations of kinetochore subcomplexes [119,154] and from native kinetochore particles [43,135,171,172] can also maintain persistent, tensionbearing attachments to assembling tips (e.g., see Figure 7). Their assembly-coupled movement in vitro is analogous to situations in vivo when kinetochores move anti-poleward in association with growing microtubule tips, such as during pre-anaphase chromosome oscillations, or during transient reversals of anaphase A chromosome-to-pole movement.…”