1. ¹Department of Biochemistry, Ajou University School of Medicine, Suwon, Korea
2. ²Department of Oncology, University of Alberta, Edmonton, Alberta, Canada
3. ³Korea Institute for Radiological and Medical Sciences, Seoul, Korea
4. ⁴Division of Gene Regulation, Institute for Advanced Medical Research, Keio University School of Medicine, Tokyo, Japan

Correspondence: Professor Dr H Cho, Department of Biochemistry, Ajou University School of Medicine, 5 Wonchon-dong, Yeongtong-gu, Suwon, Kyunggi-do, 443-721, Republic of Korea. E-mail: hscho@ajou.ac.kr; Professor Dr GK Chan, Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, Alberta, Canada. E-mail: gkc@ualberta.ca

Received 10 August 2007; Revised 9 November 2007; Accepted 20 November 2007; Published online 14 January 2008.

Abstract

Accurate chromosomal segregation is monitored by the mitotic checkpoint, and an increased rate of chromosomal missegregation leads to chromosomal instability (CIN). Here, we demonstrate that the HBV X protein (HBx) binds BubR1, a component of the mitotic checkpoint complex and co-localizes with BubR1 at the kinetochores. HBx binding to BubR1 attenuates the association between BubR1 and CDC20, an activator of the anaphase-promoting complex/cyclosome (APC/C) and induces slippage of mitotic arrest in the presence of microtubule poisons. In addition, HBx binding to BubR1 results in the accumulation of lagging chromosomes and chromosome bridges. In contrast, a C-terminally truncated HBx mutant (HBx^1–100) fails to bind BubR1 and does not cause aberrant chromosomal segregation. This provides a novel mechanism for dysregulation of the mitotic checkpoint by a viral pathogen linking it to the accumulation of chromosomal instability in HBV-associated hepatocarcinogenesis.