Target-identification and mechanism-of-action studies of indole terpenoid mimics reveal that proper spindle microtubule assembly is essential for Cdh1-mediated proteolysis of CENP-A

Abstract

AbstractCentromere protein A (CENP-A) is a centromere-specific protein that determines kinetochore positioning and the accuracy of chromosome segregation. Despite its recognized importance in maintaining mitotic fidelity, the molecular details of CENP-A regulation in mitosis are still obscure. We performed a structure-activity relationship (SAR) study of the cell cycle-arresting indole terpenoid mimic JP18 and identified two more potent analogues, (+)-6-Br-JP18 and (+)-6-Cl-JP18. Tubulin was identified as a potential protein target of these two halogenated analogues by using the drug affinity responsive target stability (DARTS) based method. X-ray crystallographic analysis determined that (+)-6-Br-JP18 and (+)-6-Cl-JP18 bind to the colchicine-binding site of β-tubulin. We further found that treatment of cancer cells with microtubule-targeting agents (MTAs), including these two compounds, upregulated CENP-A by destabilizing Cdh1, an E3 ubiquitin ligase component. The mechanistic study revealed that Cdh1 mediates proteolysis of CENP-A in mitosis, specifying the role of Cdh1 in maintaining mitotic fidelity.