MKLP2 functions in early mitosis to ensure proper chromosome congression

Abstract

Mitotic kinesin-like protein 2 (MKLP2) is a motor protein with a well-established function in promoting cytokinesis. However, our results with siRNAs targeting MKLP2 and small molecule inhibitors of MKLP2 (MKLP2i) along with the observations of others suggested a function earlier in mitosis, prior to anaphase. In this study we provide direct evidence that MKLP2 facilitates chromosome congression in prometaphase. We employed live imaging to observe HeLa cells with fluorescently tagged histones treated with MKLP2i and discovered a pronounced chromosome congression defect. We show that MKLP2 inhibited cells had a significant increase in unstable kinetochore-microtubule attachments due to impaired error correction of syntelic attachments. We propose that MKLP2 mediates kinetochore microtubule attachment stability by regulating Aurora Kinase and a downstream target, pHEC1 (Ser 55). Lastly, we show that MKLP2 inhibition results in aneuploidy, confirming that MKLP2 safeguards cells against chromosomal instability.

Design, Synthesis, and Biological Evaluation of Apcin-Based CDC20 Inhibitors

“…The decreased levels of cyclin B1 and securin in MDA-MB-468 tested with 22 and 25 at 30 μM paralleled decreased CDC20 levels. Because CDC20 protein levels changed throughout the cell cycle 13,33 and peaked in mitosis, studying the effects of our more effective CDC20 inhibitors on the synchronous cells will provide direct evidence of their impacts on APC/C CDC20 substrate levels and the stability of CDC20 upon inhibitor binding. The pro-apoptotic protein Bim has been reported to be a substrate of APC/C CDC20 , and APC/C CDC20 mediated Bim degradation was suggested to suppress apoptosis in cancer cells.…”