Gamma -Tubulin Plays an Essential Role in the Coordination of Mitotic Events.


Prigozhina NL, Oakley CE, Lewis AM, Nayak T, Osmani SA, Oakley BR.

Date: 22 December 2003


Recent data from multiple organisms indicate that ?-tubulin has essential, but incompletelydefined, functions in addition to nucleating microtubule assembly. To investigate thesefunctions, we examined the phenotype of mipAD159, a cold-sensitive allele of the ?-tubulin geneof Aspergillus nidulans. Immunofluorescence microscopy of synchronized material revealedthat at a restrictive temperature mipAD159 does not inhibit mitotic spindle formation. AnaphaseA was inhibited in many nuclei, however, and after a slight delay in mitosis (about 6% of the cellcycle period), most nuclei re-entered interphase without dividing. In vivo observations ofchromosomes at a restrictive temperature revealed that mipAD159 caused a failure of thecoordination of late mitotic events (anaphase A, anaphase B and chromosomal disjunction) andnuclei re-entered interphase quickly even though mitosis was not completed successfully. Timelapsemicroscopy also revealed that transient mitotic spindle abnormalities, in particular bentspindles, were more prevalent in mipAD159 strains than in controls. In experiments in whichmicrotubules were depolymerized with benomyl, mipAD159 nuclei exited mitosis significantlymore quickly (as judged by chromosomal condensation) than nuclei in a control strain. Thesedata reveal that ?-tubulin has an essential role in the coordination of late mitotic events, and amicrotubule-independent function in mitotic checkpoint control.

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