New Interactors of the Truncated EBNA-LP Protein Identified by Mass Spectrometry in P3HR1 Burkitt's Lymphoma Cells.

Sonia Chelouah,Aude Robert,Vasily Ogryzko,Sophie Couvé,Emilie Cochet,Sandy Balkaran,Joëlle Wiels,Evelyne May

doi:10.3390/cancers10010012

Abstract

The Epstein-Barr virus nuclear antigen leader protein (EBNA-LP) acts as a co-activator of EBNA-2, a transcriptional activator essential for Epstein-Barr virus (EBV)-induced B-cell transformation. Burkitt’s lymphoma (BL) cells harboring a mutant EBV strain that lacks both the EBNA-2 gene and 3′ exons of EBNA-LP express Y1Y2-truncated isoforms of EBNA-LP (tEBNA-LP) and better resist apoptosis than if infected with the wild-type virus. In such BL cells, tEBNA-LP interacts with the protein phosphatase 2A (PP2A) catalytic subunit (PP2A C), and this interaction likely plays a role in resistance to apoptosis. Here, 28 cellular and four viral proteins have been identified by mass spectrometry as further possible interactors of tEBNA-LP. Three interactions were confirmed by immunoprecipitation and Western blotting, namely with the A structural subunit of PP2A (PP2A A), the structure-specific recognition protein 1 (SSRP1, a component of the facilitate chromatin transcription (FACT) complex), and a new form of the transcription factor EC (TFEC). Thus, tEBNA-LP appears to be involved not only in cell resistance to apoptosis through its interaction with two PP2A subunits, but also in other processes where its ability to co-activate transcriptional regulators could be important.

Highlights

Epstein-Barr virus (EBV) belongs to the human gamma herpes virus family that was initially isolated from a Burkitt’s lymphoma (BL) cell line [1]
We found the structural subunit A of phosphatase 2A (PP2A) which confirms our previous finding that PP2A interacts with tEBNA-LP [9]
We found that tEBNA-LP interacts with the following viral proteins in P3HR1 cells: BBRF1, which is involved in viral genome packaging; BORF2, the large subunit of the ribonucleoside-diphosphate reductase holoenzyme which is necessary for viral DNA synthesis; the serine-threonine kinase BGLF4, which phosphorylates numerous cellular and viral

Summary

Introduction

Epstein-Barr virus (EBV) belongs to the human gamma herpes virus family that was initially isolated from a Burkitt’s lymphoma (BL) cell line [1]. EBV was shown to be associated with other malignancies such as Hodgkin lymphoma, post-transplant lymphoproliferative disorders (PTLD), and nasopharyngeal carcinoma (NPC). The infection of B lymphocytes in vitro by EBV generates immortalized lymphoblastoid cell lines (LCLs). In latently-infected cells, EBV produces nine viral proteins, including six nuclear antigens (EBNA-1, -2, -3A, -3B, -3C and -LP) and three membrane proteins (LMP-1, 2A, and 2B), as well as two small non-coding RNAs (EBER1 and EBER2). EBV has three different latency programs, characterized by the expression of distinct combinations of proteins. Most BL cells show the latency I phenotype, in which EBNA-1 is expressed alone from the viral

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