Requirement for PRC1 subunit BMI1 in host gene activation by Epstein-Barr virus protein EBNA3C.

Kostas Paschos,Martin J Allday,Jonathan Lees,Paul J Farrell,Quentin Bazot

doi:10.1093/nar/gky1323

Kostas Paschos, Martin J Allday + Show 3 more

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https://doi.org/10.1093/nar/gky1323

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Abstract

Epstein–Barr virus proteins EBNA3A, EBNA3B and EBNA3C control hundreds of host genes after infection. Changes in epigenetic marks around EBNA3-regulated genes suggest that they exert transcriptional control in collaboration with epigenetic factors. The roles of polycomb repressive complex (PRC)2 subunit SUZ12 and of PRC1 subunit BMI1 were assessed for their importance in EBNA3-mediated repression and activation. ChIP-seq experiments for SUZ12 and BMI1 were performed to determine their global localization on chromatin and analysis offered further insight into polycomb protein distribution in differentiated cells. Their localization was compared to that of each EBNA3 to resolve longstanding questions about the EBNA3–polycomb relationship. SUZ12 did not co-localize with any EBNA3, whereas EBNA3C co-localized significantly and co-immunoprecipitated with BMI1. In cells expressing a conditional EBNA3C, BMI1 was sequestered to EBNA3C-binding sites after EBNA3C activation. When SUZ12 or BMI1 was knocked down in the same cells, SUZ12 did not contribute to EBNA3C-mediated regulation. Surprisingly, after BMI1 knockdown, EBNA3C repressed equally efficiently but host gene activation by EBNA3C was impaired. This overturns previous assumptions about BMI1/PRC1 functions during EBNA3C-mediated regulation, for the first time identifies directly a host factor involved in EBNA3-mediated activation and provides a new insight into how PRC1 can be involved in gene activation.

Highlights

Epstein–Barr virus (EBV) is a herpesvirus that asymptomatically infects most of the human population
ChIP-seq was performed to study the localization of BMI1 and SUZ12 across the host genome in an lymphoblastoid cell line (LCL) produced by infection of 1o B cells with a recombinant EBV of B95.8 background
The 1o B cells came from the same donor as that used in a previous study [22] to identify genomic localization of EBV latent proteins EBNA3A, EBNA3B and EBNA3C. 7623 BMI1 and 1589 SUZ12 peaks were identified using the MACS algorithm (Supplementary File S1)

Summary

Introduction

Epstein–Barr virus (EBV) is a herpesvirus that asymptomatically infects most of the human population. It is the causative agent of benign lymphoproliferative disease infectious mononucleosis [1] and is associated with several malignancies, mainly of B-cell origin, and epithelial nasopharyngeal carcinomas and gastric carcinomas [2,3,4]. Activation of B cells is a necessary step in the life cycle of the virus, imitating normal B-cell differentiation, which probably requires passage of the infected cells through the germinal centre on their way to becoming latently infected, resting memory B cells, where viral gene expression is shut down. EBNA3A, EBNA3B and EBNA3C studied here have been shown to affect the expression of thousands of host genes, with EBNA3A and EBNA3C together able to act as repressors or activators and EBNA3B seemingly acting only as repressor [7]

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