Regulation of APC/CCdc20 activity by RASSF1A–APC/CCdc20 circuitry

• Published in: Oncogene Vol. 31; no. 15; pp. 1975 - 1987
• Main Authors: Chow, C, Wong, N, Pagano, M, Lun, S W-M, Nakayama, K-I, Nakayama, K, Lo, K-W
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 12.04.2012; Nature Publishing Group
• Subjects: Adenomatous Polyposis Coli Protein - metabolism; Apoptosis; Aurora Kinase B; Aurora Kinases; Cdc20 Proteins; Cell Biology; Cell Cycle Proteins - metabolism; Cell division; Cyclin A - metabolism; Gene expression; HEK293 Cells; HeLa Cells; Human Genetics; Humans; Internal Medicine; Kinases; Medicine; Medicine & Public Health; Mitosis; Oncology; Original; original-article; Phosphorylation; Protein-Serine-Threonine Kinases - metabolism; RNA Interference; Transfection; Tumor Suppressor Proteins - metabolism; Ubiquitination; APC/C; Aurora; mitotic checkpoint; RASSF1A; ubiquitination
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/onc.2011.372

RASSF1A is a key tumor-suppressor gene that is often inactivated in a wide variety of solid tumors. Studies have illustrated that RASSF1A plays vital roles in the regulation of cell-cycle progression and functions as a guardian of mitosis. Nevertheless, the precise mechanism of RASSF1A-dependent regulation of mitosis remains largely unclear. APC/C Cdc20 is the master switch and regulator of mitosis. The activity of APC/C Cdc20 is tightly controlled by phosphorylation and specific inhibitors to ensure the sequential ubiquitination of downstream targets. Here, we report on the novel finding of a regulated circuitry that controls the timely expression and hence activity of APC/C Cdc20 during mitosis. Our study showed that RASSF1A and APC/C Cdc20 form a molecular relay that regulates the APC/C Cdc20 activity at early mitosis. We found that RASSF1A inhibits APC/C Cdc20 function through its D-box motifs. Paradoxically, RASSF1A was also demonstrated to be ubiquitinated by APC/C Cdc20 in vitro and degraded at prometaphase despite of active spindle checkpoint presence. The first two unique D-boxes at the N-terminal of RASSF1A served as specific degron recognized by APC/C Cdc20 . Importantly, we found that Aurora A and Aurora B directly phosphorylate RASSF1A, a critical step by which RASSF1A switches from being an inhibitor to a substrate of APC/C Cdc20 during the course of mitotic progression. As a result of RASSF1A degradation, APC/C Cdc20 can then partially activate the ubiquitination of Cyclin A in the presence of spindle checkpoint. This circuitry is essential for the timely degradation of Cyclin A. To conclude, our results propose a new model for RASSF1A–APC/C Cdc20 interaction in ensuring the sequential progression of mitosis.