Is cohesin required for spindle-pole-body/centrosome cohesion?

Abstract

Centrosomes are microtubule-organizing centers that nucleate spindle microtubules during cell division. In budding yeast, the centrosome, often referred to as the spindle pole body, shares structural components with the centriole, the central core of the animal centrosome. The parental centrosome is duplicated when DNA replication takes place. Like sister chromatids tethered together by cohesin, duplicated centrosomes are linked and then separate to form the bipolar spindle necessary for chromosome segregation. Recent studies have shown that cohesin is also localized to the animal centrosome and is perhaps directly involved in engaging paired centrioles. Here we discuss the potential role of cohesin in mediating spindle-pole-body cohesion in the context of yeast meiosis. We propose that the coordination of chromosome segregation with centrosome cohesion and duplication is mediated by the antagonistic interaction between the Aurora kinase and the Polo kinase and that the role of cohesin in centrosome regulation appears to be indirect in budding yeast.

Keywords: SPB cohesion; centrosome; cohesin; meiosis; spindle pole body (SPB).

Figure 1.

Requirement for cohesin for SPB cohesion and duplication during yeast meiosis. (A) A schematic diagram showing spindle pole body (SPB, centrosome) and chromosome segregation during meiosis. Chromosomes are shown as gray and black bars; SPB, green dots; cohesin, red dots; microtubules, green lines. (B) Live-cell fluorescence microscopy showing SPB dynamics in wild type (WT) and rec8Δ cells during yeast meiosis. SPBs are marked by Spc42‑GFP. Projected images from eight z-stacks with 1‑μm optical sectioning are shown. Exposure time for each optical section was 100 ms. Time zero is defined as the point of SPB separation in meiosis I. Time lapse was 2 min. Note that SPBs are only loosely connected before separation in rec8Δ cells. (C) Pole-to-pole distance from WT and rec8Δ cells as shown in B. MI spindle, purple; MII spindle, other colors. (D) Live-cell fluorescence microscopy showing SPB and microtubule spindle dynamics during yeast meiosis in a REC8NC (Rec8-noncleavable¹⁹) cell. SPBs are marked by Tub4 (g‑tubulin)-GFP, microtubules by Tub1 (a‑tubulin)-mApple. Projected images from seven z-stacks with 1-μm optical sectioning are shown. Exposure time for each optical section was 60 ms. Time zero was defined as in B. Time-lapse was 3 min. Time in minutes is shown below each frame. * indicates the time of spindle recovery after breakage. Bars, 2 μm.