MTOC formation during mitotic exit in fission yeast.
Microtubules polymerise from nucleation templates containing gamma tubulin. These templates are generally concentrated in discrete structures called microtubule organising centres (MTOCs). In Schizosaccharomyces pombe, an equatorial MTOC (EMTOC) forms mid-way through anaphase B and then disassembles during the final stages of cell separation. We show that the EMTOC was generated by recruiting gamma tubulin to the equatorial F-actin ring before it constricted to cleave the cell in two during cytokinesis. The EMTOC was not a continuous ring. It had a variable structure ranging from a horseshoe to a number of short bars. EMTOC integrity depended upon the integrity of the F-actin but not the microtubule cytoskeleton. EMTOC assembly required the activity of both the septation-inducing network (SIN) that regulates the onset of cytokinesis and the anaphase-promoting complex. Activation of the SIN in interphase cells induced F-actin ring formation and contraction and the synthesis of the primary septum but did not promote EMTOC assembly. In contrast, overproduction of the polo-like kinase, Plo1, which also induced multiple rounds of septation in interphase cells, induced EMTOC formation. Thus, the network governing EMTOC formation shared many of the regulatory elements that control cytokinesis but was more complex and revealed an additional function for Plo1 during mitotic exit.
Heitz
M J
MJ
School of Biological Sciences, 2.205 Stopford Building, University of Manchester, Stopford Building, Oxford Road, Manchester M13 9PT, UK.
Petersen
J
J
Valovin
S
S
Hagan
I M
IM
D000199:Actins / Q000378:metabolism; D000705:Anaphase / Q000502:physiology; D064173:Anaphase-Promoting Complex-Cyclosome; D002453:Cell Cycle / Q000502:physiology; D029721:Drosophila Proteins; D007106:Immune Sera / Q000378:metabolism; D008025:Ligases / Q000502:physiology; D018613:Microscopy, Confocal; D022101:Microtubule-Organizing Center / Q000378:metabolism* / Q000502:physiology; D008870:Microtubules / Q000378:metabolism / Q000502:physiology; D008938:Mitosis / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis; D012568:Schizosaccharomyces / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism*; D008941:Spindle Apparatus / Q000378:metabolism; D014404:Tubulin / Q000276:immunology; D043743:Ubiquitin-Protein Ligase Complexes
D000199:Actins; D029721:Drosophila Proteins; D007106:Immune Sera; D014404:Tubulin; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D017346:Protein Serine-Threonine Kinases; D008025:Ligases