Advertisement

EBV latent membrane protein 2A orchestrates p27kip1 degradation via Cks1 to accelerate MYC-driven lymphoma in mice

Kamonwan Fish, Richard P. Sora, Samantha J. Schaller, Richard Longnecker and Masato Ikeda

Key points

  • LMP2A enhances MYC expression resulting in the rapid degradation of p27kip1 tumor suppressor via Cks1, a member of SCFSkp2 complex

  • Loss of Cks1 restores levels of p27kip1 tumor suppressor and prolongs LMP2A-mediated lymphomagenesis

Abstract

Epstein-Barr virus (EBV) establishes lifelong infection in B lymphocytes of most human hosts and is associated with several B lymphomas. During latent infection, EBV encodes latent membrane protein 2A (LMP2A) to promote survival of B cells by mimicking host B-cell receptor (BCR) signaling. Studying the roles of LMP2A during lymphoma development in vivo, we found that LMP2A mediates rapid MYC-driven lymphoma onset by allowing B cells to bypass MYC-induced apoptosis mediated by the p53 pathway in our transgenic mouse model. However, the mechanisms employed by LMP2A to facilitate transformation remain elusive. In our current study, we demonstrate a key role of LMP2A in promoting hyperproliferation of B cells by enhancing MYC expression and MYC-dependent degradation of p27kip1 tumor suppressor. Loss of the adaptor protein Cks1, a cofactor of SCFSkp2 ubiquitin ligase complex and a downstream target of MYC, increases p27kip1 expression during a pre-malignant stage. In mice expressing LMP2A, Cks1 deficiency reduces spleen weights, restores B-cell follicle formation, impedes cell cycle progression of pretumor B cells, and eventually prolongs MYC-driven tumor onset. This study demonstrates that LMP2A utilizes the role of MYC in the cell cycle, particularly in the p27kip1 degradation process, to accelerate lymphomagenesis in vivo. Thus, our results reveal a novel mechanism of EBV in diverting the functions of MYC in malignant transformation and provide a rationale for targeting EBV's roles in cell cycle modulation.

  • Submitted July 18, 2017.
  • Accepted October 19, 2017.