Synergistic role of fission yeast Alp16GCP6 and Mzt1MOZART1 in ?-tubulin complex recruitment to mitotic spindle pole bodies and spindle assembly.

ABSTRACT: In fission yeast, ?-tubulin ring complex (?TuRC)-specific components Gfh1(GCP4), Mod21(GCP5), and Alp16(GCP6) are nonessential for cell growth. Of these deletion mutants, only alp16? shows synthetic lethality with temperature-sensitive mutants of Mzt1(MOZART1), a component of the ?TuRC required for recruitment of the complex to microtubule-organizing centers. ?-Tubulin small complex levels at mitotic spindle pole bodies (SPBs, the centrosome equivalent in fungi) and microtubule levels for preanaphase spindles are significantly reduced in alp16? cells but not in gfh1? or mod21? cells. Furthermore, alp16? cells often form monopolar spindles and frequently lose a minichromosome when the spindle assembly checkpoint is inactivated. Alp16(GCP6) promotes Mzt1-dependent ?TuRC recruitment to mitotic SPBs and enhances spindle microtubule assembly in a manner dependent on its expression levels. Gfh1(GCP4) and Mod21(GCP5) are not required for Alp16(GCP6)-dependent ?TuRC recruitment. Mzt1 has an additional role in the activation of the ?TuRC for spindle microtubule assembly. The ratio of Mzt1 to ?TuRC levels for preanaphase spindles is higher than at other stages of the cell cycle. Mzt1 overproduction enhances spindle microtubule assembly without affecting ?TuRC levels at mitotic SPBs. We propose that Alp16(GCP6) and Mzt1 act synergistically for efficient bipolar spindle assembly to ensure faithful chromosome segregation.

SUBMITTER: Masuda H 

PROVIDER: S-EPMC4884066 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature