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

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.

SUBMITTER: Chelouah S

PROVIDER: S-EPMC5789362 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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

Chelouah Sonia S Cochet Emilie E Couvé Sophie S Balkaran Sandy S Robert Aude A May Evelyne E Ogryzko Vasily V Wiels Joëlle J

Cancers 20180105 1

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 phosphata ...[more]

PMID: 29303964

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Project description:The Epstein-Barr virus (EBV) EBNA-LP and EBNA2 proteins are the first to be synthesized during establishment of latent infection in B lymphocytes. EBNA2 is a key transcriptional regulator of both viral and cellular gene expression and is essential for EBV-induced immortalization of B lymphocytes. EBNA-LP is also important for EBV-induced immortalization of B lymphocytes, but far less is known about the functional domains and cellular cofactors that mediate EBNA-LP function. While recent studies suggest that serine phosphorylation of EBNA-LP and coactivation of EBNA2-mediated transactivation are important, more detailed mutational and genetic studies are complicated by the repeat regions that comprise the majority of the EBNA-LP sequence. Therefore, we have used a comparative approach by studying the EBNA-LP homologues from baboon and rhesus macaque lymphocryptoviruses (LCVs) (baboon LCV and rhesus LCV). The predicted baboon and rhesus LCV EBNA-LP amino acid sequences are 61 and 64% identical to the EBV EBNA-LP W1 and W2 exons and 51% identical to the EBV EBNA-LP Y1 and Y2 exons. Five evolutionarily conserved regions can be defined, and four of eight potential serine residues are conserved among all three EBNA-LPs. The major internal repeat sequence also revealed a highly conserved Wp EBNA promoter with strong conservation of upstream activating sequences important for Wp transcriptional regulation. To test whether transcriptional coactivating properties were common to the rhesus LCV EBNA-LP, a rhesus LCV EBNA2 homologue was cloned and expressed. The rhesus LCV EBNA2 transcriptionally transactivates EBNA2-responsive promoters through a CBF1-dependent mechanism. The rhesus LCV EBNA-LP was able to further enhance rhesus LCV or EBV EBNA2 transactivation 5- to 12-fold. Thus, there is strong structural and functional conservation among the simian EBNA-LP homologues. Identification of evolutionarily conserved serine residues and regions in EBNA-LP homologues provides important clues for identifying the cellular cofactors and molecular mechanisms mediating these conserved viral functions.

Project description:BackgroundBurkitt's lymphoma is an aggressive B-cell lymphoma that occurs in children and adults and is largely curable with the use of intensive and toxic chemotherapy. Current treatments are less effective and have more severe side effects in adults and patients with immunodeficiency than in children.MethodsWe studied low-intensity treatment consisting of infused etoposide, doxorubicin, and cyclophosphamide with vincristine, prednisone, and rituximab (EPOCH-R) in patients with untreated Burkitt's lymphoma. Two EPOCH-R regimens were tested: a standard dose-adjusted combination in human immunodeficiency virus (HIV)-negative patients (DA-EPOCH-R group) and a lower-dose short-course combination with a double dose of rituximab in HIV-positive patients (SC-EPOCH-RR group).ResultsA total of 30 consecutive patients were treated; 19 patients were in the DA-EPOCH-R group, and 11 in the SC-EPOCH-RR group. The overall median age of the patients was 33 years, and 40% were 40 years of age or older; 73% of the patients had intermediate-risk disease, and 10% had high-risk disease. The principal toxic events, fever and neutropenia, were observed during 22% of the DA-EPOCH-R treatment cycles and 10% of the SC-EPOCH-RR treatment cycles. The tumor lysis syndrome developed in 1 patient; no treatment-related deaths occurred. The median cumulative doses of doxorubicin-etoposide and cyclophosphamide administered in the SC-EPOCH-RR group were 47% and 57% lower, respectively, than those administered in the DA-EPOCH-R group. With median follow-up times of 86 months in the DA-EPOCH-R group and 73 months in the SC-EPOCH-RR group, the rates of freedom from progression of disease and overall survival were, respectively, 95% and 100% with DA-EPOCH-R and 100% and 90% with SC-EPOCH-RR. None of the patients died from Burkitt's lymphoma.ConclusionsIn this uncontrolled prospective study, low-intensity EPOCH-R-based treatment was highly effective in adults with sporadic or immunodeficiency-associated Burkitt's lymphoma. (Funded by the National Cancer Institute; ClinicalTrials.gov numbers, NCT00001337 and NCT00006436.).

Dataset Information

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

Publications

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

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