Deregulation of Rb-E2F1 Axis Causes Chromosomal Instability by Engaging the Transactivation Function of Cdc20–Anaphase-Promoting Complex/Cyclosome

Abstract

The E2F family of transcription factors regulates genes involved in various aspects of the cell cycle. Beyond the well-documented role in G₁/S transition, mitotic regulation by E2F has also been reported. Proper mitotic progression is monitored by the spindle assembly checkpoint (SAC). The SAC ensures bipolar separation of chromosomes and thus prevents aneuploidy. There are limited reports on the regulation of the SAC by E2F. Our previous work identified the SAC protein Cdc20 as a novel transcriptional regulator of the mitotic ubiquitin carrier protein UbcH10. However, none of the Cdc20 transcription complex proteins have any known DNA binding domain. Here we show that an E2F1-DP1 heterodimer is involved in recruitment of the Cdc20 transcription complex to the UBCH10 promoter and in transactivation of the gene. We further show that inactivation of Rb can facilitate this transactivation process. Moreover, this E2F1-mediated regulation of UbcH10 influences mitotic progression. Deregulation of this pathway results in premature anaphase, chromosomal abnormalities, and aneuploidy. We conclude that excess E2F1 due to Rb inactivation recruits the complex of Cdc20 and the anaphase-promoting complex/cyclosome (Cdc20-APC/C) to deregulate the expression of UBCH10, leading to chromosomal instability in cancer cells.

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.00868-14.

ACKNOWLEDGMENTS

This work was supported by a Department of Biotechnology grant (BT/PR/5524/Med/14/649/2004, BT/01/COE/05/04) and by Council of Scientific and Industrial Research grant IAP 001, awarded to S.R. Predoctoral fellowships to S.N. and A.C. were supported by the Council of Scientific and Industrial Research (New Delhi, India), one to A.G. was supported by the Advanced Centre for Treatment, Research and Education in Cancer, Tata Memorial Centre (Navi Mumbai, India), and one to S.D. was supported by the Department of Biotechnology, India.

We thank Diptadeep Sarkar (Olympus), Samit Adhya, Suvendra Nath Bhattacharyya, and Keya Chaudhuri (CSIR-Indian Institute of Chemical Biology, India) for microscopic analysis, Shantanu Chowdhury (Institute of Genomics and Integrative Biology, India) for bioinformatic analysis, and Anushila Gangopadhyay (BD Biosciences) for technical assistance with the operation of the BD LSR Fortessa FACS instrument. The plasmid pCMV-E2Ftr was kindly provided by Jorge G. Gomez-Gutierrez (James Graham Brown Cancer Center, Louisville, KY). The plasmids pCMV-HA-ER-E2F1 DBD and pCMV-HA-ER-E2F1 were kindly provided by Peggy Farnham (University of Southern California, Los Angeles, CA).

We have no conflicts of interest.