Regulation of cytokinesis by aurora B kinase

In the first part of this thesis, I identify 14-3-3 protein as an interaction partner of an Aurora-phosphorylated region of MKLP1, the kinesin component of centralspindlin. I show that MKLP1 contains a highly conserved amino acid motif that encompasses a known Aurora B phosphorylation site, S708, and binds 14-3-3 when phosphorylated at a conserved serine, S710. Aurora-mediated phosphorylation of S708 inhibits binding of 14-3-3 to MKLP1. Given that S708-phosphorylated MKLP1 (which cannot bind 14-3-3) becomes highly enriched at the central spindle during anaphase, whereas S710-phosphorylated MKLP1 (which can bind 14-3-3) does not, these results suggest that Aurora B regulates centralspindlin by controlling the binding and release of 14-3-3 at different subcellular structures during cell division. Finally, I investigate whether regulated binding of MKLP1 to 14-3-3 is required for centralspindlin function and cytokinesis. I show that the sole function of Aurora-mediated S708 phosphorylation is the removal of 14-3-3 that is bound to MKLP1, and that this is required for stable binding of MKLP1 to the central spindle. 14-3-3 is necessary and sufficient to prevent the assembly of centralspindlin into higher order multimers that are known to be required for centralspindlin to bind and bundle microtubules. Collectively, these findings show that Aurora B regulates cytokinesis by releasing MKLP1 from 14-3-3 protein, enabling centralspindlin to assemble into higher order multimers that bind and bundle microtubules into the central spindle.EThOS - Electronic Theses Online ServiceGBUnited Kingdo