UNUSUALLY HIGH-FREQUENCY OF A 69-BP DELETION WITHIN THE CARBOXY-TERMINUS OF THE LMP-1 ONCOGENE OF EPSTEIN-BARR-VIRUS DETECTED IN BURKITTS-LYMPHOMA OF TURKISH CHILDREN

Burkitt's lymphoma (BL) in Turkish children is commonly associated wit h Epstein-Barr virus (EBV) infection. The C-terminus of the latent mem brane protein 1 (LMP-1) of EBV is essential for transformation and the 30-bp deletion detected in this region has been implicated to be asso ciated with a more aggressive malignant phenotype. To understand the m olecular mechanisms underlying EBV pathogenesis in BL of Turkish child ren, we analyzed 30-bp deletion and 33-bp variable repeat regions of t he LMP-1 gene from paraffin-embedded tumor tissues of 30 BL patients ( mean age 5.9 years). Primer pairs spanning the 30-bp deletion and 33-b p repeat regions were designed far amplification by polymerase chain r eaction (PCR). The PCR-amplified products were analyzed by gel electro phoresis, Southern blot hybridization, and DNA sequencing. Twenty-eigh t (93%) of 30 BL biopsy samples were EBV positive as determined by PCR . Variable copy numbers (ranging from 4.5 to 7) of the 33-bp repeat of LMP-1 gene were detected in these EBV-containing tumor samples. To de termine the frequency of the 30-bp deletion of the LMP-1 gene, we sequ enced the amplimers encompassing this region. Analyses of DNA sequence of 28 Turkish BLs have disclosed four patterns: the first (32% (9/28) ) is identical to B95-8 with no deletion, the second (11% (3/28)) Is i dentical to Asian NPC CAO strain with 30-bp deletion, the third (46% ( 13/28)) is prevalent in Turkish BLs with a longer deletion (69 bp), an d the fourth (11% (3/28)) consists of a mixture of 30-bp and 69-bp del etion. The occurrence of high frequency of the 69-bp deletion appears to have no correlation with the disease site. Mutations found in the C AO strain were also detected in the Turkish BL clustering at the amino acids 322, 334, 338 and 342; whereas mutations specific for Turkish B L were clustered at amino acids 326, 352 and 361. To assess the EBV ge notype with the changes in C-terminus of LMP-1 gene, we performed geno typing by PCR to differentiate type A and B strain. All 28 patients we re infected by type A EBV. Such a high frequency of the larger size (6 9 bp) deletion has never been reported. Ascertaining the role of this deletion in BL pathogenesis will require further study.