MTOC formation during mitotic exit in fission yeast

Area of Science:

• Cell Biology
• Cytoskeleton Dynamics
• Molecular Cell Biology

Background:

• Microtubules polymerize from nucleation templates containing gamma tubulin.
• Microtubule organizing centers (MTOCs) concentrate these templates.
• In Schizosaccharomyces pombe, an equatorial MTOC (EMTOC) forms during anaphase B and disassembles during cell separation.

Purpose of the Study:

• To investigate the formation and regulation of the equatorial MTOC during cytokinesis in Schizosaccharomyces pombe.
• To elucidate the relationship between the F-actin ring, the septation-inducing network (SIN), and MTOC assembly.

Main Methods:

• Recruitment of gamma tubulin to the equatorial F-actin ring.
• Analysis of EMTOC structure and integrity.
• Investigating the roles of the SIN and anaphase-promoting complex in EMTOC assembly.
• Examining the effect of Plo1 overproduction on EMTOC formation.

Main Results:

• The EMTOC is generated by recruiting gamma tubulin to the equatorial F-actin ring prior to cytokinesis.
• EMTOC structure is variable (horseshoe to bars) and depends on F-actin integrity, not microtubules.
• EMTOC assembly requires the SIN and anaphase-promoting complex.
• Plo1 overproduction induces EMTOC formation, suggesting a role in mitotic exit.

Conclusions:

• The equatorial MTOC formation is linked to F-actin ring constriction during cytokinesis.
• EMTOC assembly involves regulatory elements of cytokinesis but is more complex.
• Plo1 has an additional function in mitotic exit related to EMTOC formation.