Induction of p16INK4a Is the Major Barrier to Proliferation when Epstein-Barr Virus (EBV) Transforms Primary B Cells into Lymphoblastoid Cell Lines. e1003187

• Published in: PLoS pathogens 2013-02, Vol.9 (2)
• Main Authors: Skalska, Lenka, White, Robert E, Parker, Gillian A, Sinclair, Alison J, Paschos, Kostas, Allday, Martin J
• Format: Article
• Language: English
• Subjects: Epstein-Barr virus
• ISSN: 1553-7374
• DOI: 10.1371/journal.ppat.1003187

To explore the role of p16INK4a as an intrinsic barrier to B cell transformation by EBV, we transformed primary B cells from an individual homozygous for a deletion in the CDKN2A locus encoding p16INK4a and p14ARF. Using recombinant EBV-BAC viruses expressing conditional EBNA3C (3CHT), we developed a system that allows inactivation of EBNA3C in lymphoblastoid cell lines (LCLs) lacking active p16INK4a protein but expressing a functional 14ARF-fusion protein (p14/p16). The INK4a locus is epigenetically repressed by EBNA3C - in cooperation with EBNA3A - despite the absence of functional p16INK4a. Although inactivation of EBNA3C in LCLs from normal B cells leads to an increase in p16INK4a and growth arrest, EBNA3C inactivation in the p16INK4a-null LCLs has no impact on the rate of proliferation, establishing that the repression of INK4a is a major function of EBNA3C in EBV-driven LCL proliferation. This conditional LCL system allowed us to use microarray analysis to identify and confirm genes regulated specifically by EBNA3C, independently of proliferation changes modulated by the p16INK4a-Rb-E2F axis. Infections of normal primary B cells with recombinant EBV-BAC virus from which EBNA3C is deleted or with 3CHT EBV in the absence of activating ligand 4-hydroxytamoxifen, revealed that EBNA3C is necessary to overcome an EBV-driven increase in p16INK4a expression and concomitant block to proliferation 2-4 weeks post-infection. If cells are p16INK4a-null, functional EBNA3C is dispensable for the outgrowth of LCLs.