Cdk1 Activity Is Required for Mitotic Activation of Aurora A during G2/M Transition of Human Cells

Abstract

In mammalian cells entry into and progression through mitosis are regulated by multiple mitotic kinases. How mitotic kinases interact with each other and coordinately regulate mitosis remains to be fully understood. Here we employed a chemical biology approach using selective small molecule kinase inhibitors to dissect the relationship between Cdk1 and Aurora A kinases during G 2 /M transition. We find that activation of Aurora A first occurs at centrosomes at late G 2 and is required for centrosome separation independently of Cdk1 activity. Upon entry into mitosis, Aurora A then becomes fully activated downstream of Cdk1 activation. Inactivation of Aurora A or Plk1 individually during a synchronized cell cycle shows no significant effect on Cdk1 activation and entry into mitosis. However, simultaneous inactivation of both Aurora A and Plk1 markedly delays Cdk1 activation and entry into mitosis, suggesting that Aurora A and Plk1 have redundant functions in the feedback activation of Cdk1. Together, our data suggest that Cdk1, Aurora A, and Plk1 mitotic kinases participate in a feedback activation loop and that activation of Cdk1 initiates the feedback loop activity, leading to rapid and timely entry into mitosis in human cells. In addition, live cell imaging reveals that the nuclear cycle of cells becomes uncoupled from cytokinesis upon inactivation of both Aurora A and Aurora B kinases and continues to oscillate in a Cdk1-dependent manner in the absence of cytokinesis, resulting in multinucleated, polyploidy cells.

BimEL is phosphorylated at mitosis by Aurora A and targeted for degradation by βTrCP1

“…Only Aurora A has been shown to definitively require Cdk1/Cyclin B for activation during mitosis. 30 Second, Aurora A has been shown to act as a bona fide oncogene and induction of Bim degradation is consistent with this activity. Third, we observe that the Aurora A inhibitor MLN8054 prevents mitotic phosphorylation of BimEL on S93/94/98 and stabilizes the protein.…”

“…Intriguingly, mitotic activation of Aurora A has been shown to be dependent upon cdk1 activity. 30 We therefore determined if S93/94/98 is phosphorylated during mitosis by Aurora A. 293T cells were arrested using Thy/Noc and released into increasing concentrations of the Aurora kinase inhibitor MLN8054.…”

Identification of fibroblast growth factor-8b target genes associated with early and late cell cycle events in breast cancer cells

“…This suggests that aurora kinase A plays an important role in FGF8b-mediated cell proliferation but in its absence, proteins with redundant functions can overtake its actions. Plk1 might be one such protein as Aurora kinase A and Plk1 are shown to have redundant functions in activation of Cdk1 to promote entry into mitosis (Van Horn et al, 2010).…”

The Activation of MEK/ERK Signaling Pathway by Bone Morphogenetic Protein 4 to Increase Hepatocellular Carcinoma Cell Proliferation and Migration

“…We further identified that a function of BMP4 signaling can induce cyclin B1 and CDK1 overexpression in HCC cells. The complex kinase of cyclin B1 and CDK1 is an important mediator of the cell-cycle regulator, which accelerates the progress of mitosis (37)(38)(39). It was observed, through Ki-67 staining, that BMP4 triggered the synthesis of DNA, which is required for cell division, and promoted the phosphorylation of ser10 residue of histone3 known as a marker for mitotic progression (40).…”