RNA stimulates Aurora B kinase activity during mitosis.

Ashwini Jambhekar,Amy B Emerman,Michael D Blower,Caterina T H Schweidenback,Debra L Silver

doi:10.1371/journal.pone.0100748

Ashwini Jambhekar, Amy B Emerman + Show 3 more

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https://doi.org/10.1371/journal.pone.0100748

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Journal: PloS one	Publication Date: Jun 26, 2014
Citations: 50	License type: CC BY 4.0

Affiliation: Massachusetts General Hospital, Harvard University

Abstract

Accurate chromosome segregation is essential for cell viability. The mitotic spindle is crucial for chromosome segregation, but much remains unknown about factors that regulate spindle assembly. Recent work implicates RNA in promoting proper spindle assembly independently of mRNA translation; however, the mechanism by which RNA performs this function is currently unknown. Here, we show that RNA regulates both the localization and catalytic activity of the mitotic kinase, Aurora-B (AurB), which is present in a ribonucleoprotein (RNP) complex with many mRNAs. Interestingly, AurB kinase activity is reduced in Xenopus egg extracts treated with RNase, and its activity is stimulated in vitro by RNA binding. Spindle assembly defects following RNase-treatment are partially rescued by inhibiting MCAK, a microtubule depolymerase that is inactivated by AurB-dependent phosphorylation. These findings implicate AurB as an important RNA-dependent spindle assembly factor, and demonstrate a translation-independent role for RNA in stimulating AurB.

Highlights

The spindle is a macromolecular assembly of microtubules and associated proteins that controls the segregation of chromosomes during each eukaryotic cell division
To determine if AurB activity is regulated by RNA in Xenopus egg extracts, we assayed AurB activity by monitoring Op18 hyperphosphorylation [14]
To measure the kinase activity of AurB directly, we immunoprecipitated AurB using custom antibodies (Fig. S1B) and tested its ability to phosphorylate an N-terminal fragment of the AurB target MCAK [16,17] in vitro in the presence or absence of RNA (Fig. 1B–C, Fig. S1C)

Summary

Introduction

The spindle is a macromolecular assembly of microtubules and associated proteins that controls the segregation of chromosomes during each eukaryotic cell division. The major targets of this complex are two microtubule-depolymerizing proteins: Op18 [14], which binds to and sequesters free tubulin dimers [15], and MCAK [16,17], a kinesin-13 family member [18] that is the major depolymerizing activity in Xenopus egg extracts [19,20]. Both proteins are inactivated when phosphorylated by AurB during mitosis [14,16,17,21], allowing robust spindle assembly

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