MOLECULAR AND FUNCTIONAL-ANALYSIS OF THE EPSTEIN-BARR-VIRUS LMP1 ONCOGENE PROMOTER IN LYMPHOPROLIFERATIVE DISEASES

The expression of the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) oncogene is tightly regulated by viral and cellular factors. LMP1 is present in the majority of nasopharyngeal carcinoma tumor cel ls and in Reed-Sternberg cells from Hodgkin's lymphoma, in which the o nly EBV nuclear antigen detected is EBNA1. The aim of this study was t o test whether mutations affecting LMP1 gene expression were present i n lymphoproliferative disorders, and, if so, whether their presence co rrelated with the clinical course of the disease. For this purpose we characterized the LMP1 promoter region from seven cases including two patients with aggressive Hodgkin's disease and two with atypical lymph oproliferative syndromes. Our results show that the sequences -298 to +29 relative to the transcription start site diverged up to 9.3% when compared with the prototype EBV strain B95-8. The cAMP responsive-like element (CRE), located at positions -37 to -44, was found to be mutat ed in 3 of the 7 cases. Functional analysis of transfected human embry onic kidney 293 cells using the firefly luciferase reporter gene revea led that mutations within the CRE site led to a 70% mean decrease in r eporter activity. Our analysis indicates that in lymphoproliferative d isorders, naturally occurring LMP1 variants that exibit weak promoter activity are still associated with clinically progressive disease.