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Precise positioning of the mitotic spindle determines the correct cell division axis and is crucial for organism development. Spindle positioning is mediated through a cortical machinery by capturing astral microtubules, thereby generating pushing/pulling forces at the cell cortex. However, the molecular link between these two structures remains elusive. Here we describe a previously uncharacterized protein, MISP (C19orf21), as a substrate of Plk1 that is required for correct mitotic spindle positioning. MISP is an actin-associated protein throughout the cell cycle. MISP depletion led to an impaired metaphase-to-anaphase transition, which depended on phosphorylation by Plk1. Loss of MISP induced mitotic defects including spindle misorientation accompanied by shortened astral microtubules. Furthermore, we find that MISP formed a complex with and regulated the cortical distribution of the +TIP binding protein p150(glued), a subunit of the dynein-dynactin complex. We propose that Plk1 phosphorylates MISP, thus stabilizing cortical and astral microtubule attachments required for proper mitotic spindle positioning.

Original publication

DOI

10.1083/jcb.201207050

Type

Journal article

Journal

J Cell Biol

Publication Date

18/03/2013

Volume

200

Pages

773 - 787

Keywords

Anaphase, Cell Cycle Proteins, Dyneins, HeLa Cells, Humans, Metaphase, Microfilament Proteins, Microtubule-Associated Proteins, Microtubules, Phosphoproteins, Phosphorylation, Protein-Serine-Threonine Kinases, Proto-Oncogene Proteins, Spindle Apparatus