Making microtubules less MOB1-ile

Following mitosis, cells undergo cytokinesis and, ultimately, abscission to separate the two daughter cells. One of the crucial steps in abscission is the reorganization and disassembly of the microtubules that are associated with the midbody. Although it is known that the microtubule-severing enzyme spastin has a role in abscission, other regulators of midbody-associated microtubules have not yet been defined. Here, Álvaro Tavares and co-workers (p. 3085) describe a new role for the MOB1 protein family in regulating microtubule stability during cytokinesis. HeLa cells co-transfected with siRNAs against MOB1A and MOB1B are unable to separate at the end of cytokinesis. This inability to undergo abscission is the result of increased microtubule stability in cells that lack MOB1A and MOB1B. The authors also find that daughter cells depleted of these two proteins portray an increased motility following the completion of telophase and cytokinesis. In addition to being required for timely abscission, MOB1A and MOB1B are also essential for centriole cohesion. In cells that lack both proteins, the centrioles aberrantly remain separated in G1 phase. The MOB1 proteins are known to bind to and activate members of the NDR and LATS protein kinase families, which leads the authors to speculate that MOB1-dependent kinases have a role in regulating microtubule dynamics.