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Alternative EBNA1 expression in organ transplant patients
Author(s) -
Berggren Malin Å.M.,
Isaksson Åsa,
Larsson Ulrica,
Nilsson Folke,
Nyström Ulla,
Ekman Tor,
Löfvenmark Jane,
Ricksten Anne
Publication year - 2005
Publication title -
journal of medical virology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 121
eISSN - 1096-9071
pISSN - 0146-6615
DOI - 10.1002/jmv.20369
Subject(s) - internal ribosome entry site , untranslated region , biology , exon , five prime untranslated region , immunology , virology , gene , medicine , messenger rna , translation (biology) , genetics
In order to identify patients at risk for developing post‐transplant lymphoproliferative disease (PTLD), a sensitive nested RT‐PCR method for detection of EBNA1 gene expression in peripheral blood cells was used. EBNA1 expression in peripheral blood samples from 60 organ recipients was analyzed and compared with 24 healthy controls in a retrospective study. Overall, EBNA1‐positive samples were detected at least once in 43% of the transplant patients with post‐transplant lymphoproliferative disease, in 18% of the other transplant patients and in none of the healthy controls. The odds ratio for EBNA1 expression in patients with post‐transplant lymphoproliferative disease was 3.42 (95% CI = 1.02–11.54) compared to other transplant recipients. Together with normal EBV Q promoter initiated EBNA1 transcripts, an alternatively spliced form was expressed in peripheral blood cells in the above‐mentioned transplant patients. This transcript lacks the U leader exon in the 5′‐untranslated region (UTR). We have previously identified and characterized a functional internal ribosome entry site, the EBNA IRES, in the untranslated U leader exon of EBNA1. Transfection experiments with EBNA1 coding plasmids followed by Western blot showed that the EBNA IRES promotes cap‐independent translation and increases the EBNA1 protein level. The alternative EBNA1 transcript lacking this function is expressed in the majority of the investigated EBNA1‐positive patient samples as well as in some EBV‐positive B‐cell lines. Alternative splicing in this form gives EBV potential to regulate the translation of EBNA1 by modifying the 5′ UTR. These findings indicate a new mechanism for EBNA1 expression in vivo. J. Med. Virol. 76:378–385, 2005. © 2005 Wiley‐Liss, Inc.