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Figure S2 from UNC-45A Is a Novel Microtubule-Associated Protein and Regulator of Paclitaxel Sensitivity in Ovarian Cancer Cells

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posted on 2023-04-03, 17:27 authored by Ashley Mooneyham, Yoshie Iizuka, Qing Yang, Courtney Coombes, Mark McClellan, Vijayalakshmi Shridhar, Edith Emmings, Mihir Shetty, Liqiang Chen, Teng Ai, Joyce Meints, Michael K. Lee, Melissa Gardner, Martina Bazzaro

Polyclonal and clones of paclitaxel-resistant ovarian cancer cells overcome cell death on multipolar spindles

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Department of Defense Ovarian Cancer Research Program

NIH

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ARTICLE ABSTRACT

UNC-45A, a highly conserved member of the UCS (UNC45A/CRO1/SHE4P) protein family of cochaperones, plays an important role in regulating cytoskeletal-associated functions in invertebrates and mammalian cells, including cytokinesis, exocytosis, cell motility, and neuronal development. Here, for the first time, UNC-45A is demonstrated to function as a mitotic spindle-associated protein that destabilizes microtubules (MT) activity. Using in vitro biophysical reconstitution and total internal reflection fluorescence microscopy analysis, we reveal that UNC-45A directly binds to taxol-stabilized MTs in the absence of any additional cellular cofactors or other MT-associated proteins and acts as an ATP-independent MT destabilizer. In cells, UNC-45A binds to and destabilizes mitotic spindles, and its depletion causes severe defects in chromosome congression and segregation. UNC-45A is overexpressed in human clinical specimens from chemoresistant ovarian cancer and that UNC-45A–overexpressing cells resist chromosome missegregation and aneuploidy when treated with clinically relevant concentrations of paclitaxel. Lastly, UNC-45A depletion exacerbates paclitaxel-mediated stabilizing effects on mitotic spindles and restores sensitivity to paclitaxel. These findings reveal novel and significant roles for UNC-45A in regulation of cytoskeletal dynamics, broadening our understanding of the basic mechanisms regulating MT stability and human cancer susceptibility to paclitaxel, one of the most widely used chemotherapy agents for the treatment of human cancers.

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