Epstein-Barr virus nuclear antigen 2 disrupts mitotic checkpoint and causes chromosomal instability

Carcinogenesis. 2009 Feb;30(2):366-75. doi: 10.1093/carcin/bgn291. Epub 2009 Jan 6.

Abstract

The Epstein-Barr virus nuclear antigen 2 (EBNA2) plays a key role in transformation of B-lymphocytes mediated by Epstein-Barr virus (EBV) and can induce tumor formation in transgenic mice. However, the precise mechanism underlying EBNA2-mediated tumorigenesis remains elusive. Here, we report that EBNA2 can compromise mitotic spindle checkpoint (MSC) induced by the spindle inhibitor nocodazole and cause chromosomal instability (CIN) in HEp-2, U2-OS and BJAB cells. When EBNA2-expressing cells were treated with nocodazole, they exited mitosis prematurely and initiated another round of DNA synthesis. Nucleolocalization of EBNA2 was essential for EBNA2 to compromise MSC and to cause CIN. The metaphase chromosome spread data indicated that the EBNA2-expressing U2-OS cells showed a more heterogenous chromosome number distribution than the vector-transfected and parental cells. The median chromosome number for EBNA2-expressing, vector-transfected and parental U2-OS cells is 75, 65 and 64, respectively. EBNA2 was shown to be able to downregulate mitotic arrest deficient 2 (MAD2) approximately 2- to 3-fold and upregulate polo-like kinase 1 (PLK1) approximately 2-fold. The dysregulation of MAD2 and PLK1 may lead to activation of anaphase promoting complex/cyclosome and premature degradation of securin. Indeed, we found that when MSC was induced by nocodazole, securin was prematurely degraded in EBNA2-expressing cells. Finally, we show that EBNA2 could induce micronuclei and multinuclei formation in HEp-2 and U2-OS cells. Together, these studies reveal a new function of EBNA2 in cell-cycle regulation and may shed light on the role of EBNA2 in EBV-mediated tumorigenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium-Binding Proteins / metabolism
  • Cell Cycle Proteins / metabolism
  • Cell Line, Tumor
  • Cell Transformation, Neoplastic*
  • Chromosomal Instability / physiology*
  • Down-Regulation
  • Epstein-Barr Virus Nuclear Antigens / physiology*
  • Humans
  • Mad2 Proteins
  • Micronuclei, Chromosome-Defective
  • Mitosis*
  • Nocodazole / pharmacology
  • Polo-Like Kinase 1
  • Protein Serine-Threonine Kinases / metabolism
  • Proto-Oncogene Proteins / metabolism
  • Repressor Proteins / metabolism

Substances

  • Calcium-Binding Proteins
  • Cell Cycle Proteins
  • Epstein-Barr Virus Nuclear Antigens
  • MAD2L1 protein, human
  • Mad2 Proteins
  • Proto-Oncogene Proteins
  • Repressor Proteins
  • Protein Serine-Threonine Kinases
  • Nocodazole