Function and regulation of Maskin, a TACC family protein, in microtubule growth during mitosis

Abstract

The Xenopus protein Maskin has been previously identified and characterized in the context of its role in translational control during oocyte maturation. Maskin belongs to the TACC protein family. In other systems, members of this family have been shown to localize to centrosomes during mitosis and play a role in microtubule stabilization. Here we have examined the putative role of Maskin in spindle assembly and centrosome aster formation in the Xenopus egg extract system. Depletion and reconstitution experiments indicate that Maskin plays an essential role for microtubule assembly during M-phase. We show that Maskin interacts with XMAP215 and Eg2, the Xenopus Aurora A kinase in vitro and in the egg extract. We propose that Maskin and XMAP215 cooperate to oppose the destabilizing activity of XKCM1 therefore promoting microtubule growth from the centrosome and contributing to the determination of microtubule steady-state length. Further more, we show that Maskin localization and function is regulated by Eg2 phosphorylation.

Aurora A kinase and its substrate TACC3 are required for central spindle assembly

“…Interestingly, AurA has been shown to be required for MT nucleation/stabilization through the RanGTP-dependent pathway in the early phases of mitosis [4,8,18]. We have shown here that AurA kinase activity is required during anaphase for central spindle assembly.…”

VX-680 Inhibits Aurora A and Aurora B Kinase Activity in Human Cells

“…The phosphorylation of TACC3 on centrosomes has previously been shown to be required for the centrosome-dependent assembly of microtubules, and TACC3 phosphorylated by Aurora A has been demonstrated through depletion studies to be targeted to the centrosome in mitosis. 10,35,36 Consistently, VX-680 also targets both Aurora A and Aurora B kinase activity in cells through blockade of T-loop phosphorylation. Our finding that Aurora B phosphorylation at Thr232 is sensitive to both VX-680 and ZM447439 (Fig.…”

Aurora kinases and spindle assembly: Variations on a common theme?

“…By contrast, the role of AurA in centrosome-mediated spindle assembly has mainly been linked to its participation in centrosome maturation, i.e., in the recruitment to and activation at centrosomes of SAFs (e.g., γ-tubulin and TACC3/ maskin) that promote MT nucleation and growth. 24,53,56,[77][78][79][80][81] In this instance, AurA is first targeted to and activated at centrosomes by Cep192, 53 and only then it can phosphorylate centrosomal proteins. Our experiments suggest that an intact AurACep192 interaction is essential only for the targeting of AurA to centrosomes and for the step that links kinase dimerization to its activation.…”