The EBV Latent Antigen 3C Inhibits Apoptosis through Targeted Regulation of Interferon Regulatory Factors 4 and 8

• Published in: PLoS pathogens 2013-05, Vol.9 (5), p.e1003314
• Main Authors: Banerjee, Shuvomoy, Lu, Jie, Cai, Qiliang, Saha, Abhik, Jha, Hem Chandra, Dzeng, Richard Kuo, Robertson, Erle S
• Format: Article
• Language: English
• Subjects: Apoptosis; B-Lymphocytes - metabolism; B-Lymphocytes - pathology; B-Lymphocytes - virology; Biology; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; Cell growth; Cell Line, Tumor; Cell Proliferation; Cell Transformation, Viral - genetics; Cellular control mechanisms; Control; Epstein-Barr Virus Nuclear Antigens - genetics; Epstein-Barr Virus Nuclear Antigens - metabolism; Experiments; Gene expression; Genetic testing; HEK293 Cells; Herpesvirus 4, Human - genetics; Herpesvirus 4, Human - metabolism; Humans; Interferon Regulatory Factors - genetics; Interferon Regulatory Factors - metabolism; Lymphocytes; Properties; Proteins; Regulation; Signal transduction; Signal Transduction - genetics; Studies; Testing; Transcription factors
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1003314

Epstein-Barr virus (EBV) is linked to a broad spectrum of B-cell malignancies. EBV nuclear antigen 3C (EBNA3C) is an encoded latent antigen required for growth transformation of primary human B-lymphocytes. Interferon regulatory factor 4 (IRF4) and 8 (IRF8) are transcription factors of the IRF family that regulate diverse functions in B cell development. IRF4 is an oncoprotein with anti-apoptotic properties and IRF8 functions as a regulator of apoptosis and tumor suppressor in many hematopoietic malignancies. We now demonstrate that EBNA3C can contribute to B-cell transformation by modulating the molecular interplay between cellular IRF4 and IRF8. We show that EBNA3C physically interacts with IRF4 and IRF8 with its N-terminal domain in vitro and forms a molecular complex in cells. We identified the Spi-1/B motif of IRF4 as critical for EBNA3C interaction. We also demonstrated that EBNA3C can stabilize IRF4, which leads to downregulation of IRF8 by enhancing its proteasome-mediated degradation. Further, si-RNA mediated knock-down of endogenous IRF4 results in a substantial reduction in proliferation of EBV-transformed lymphoblastoid cell lines (LCLs), as well as augmentation of DNA damage-induced apoptosis. IRF4 knockdown also showed reduced expression of its targeted downstream signalling proteins which include CDK6, Cyclin B1 and c-Myc all critical for cell proliferation. These studies provide novel insights into the contribution of EBNA3C to EBV-mediated B-cell transformation through regulation of IRF4 and IRF8 and add another molecular link to the mechanisms by which EBV dysregulates cellular activities, increasing the potential for therapeutic intervention against EBV-associated cancers.