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Abstract: Epstein-Barr virus (EBV) BZLF1 gene can trigger EBV from latent infection to lytic replicative phase. The functions of BZLF1 are well known, while little is known about its gene polymorphism. In order to elucidate the sequence variations of BZLF1 and its association with malignancies, we analyzed BZLF1 gene in 24 EBV-associated gastric carcinomas, 41 nasopharyngeal carcinomas and 24 throat washing samples from healthy donors in Northern China using PCR-direct sequencing method. Three types and 8 subtypes of BZLF1 were identified. A dominant type BZLF1-A was found in 67 of 89 (75.3%) isolates. Type BZLF1-B was characterized by a common Ala deletion at residue 127, which was detected in 21 of 89 isolates (23.6%). Type BZLF1-C contained only one isolate (GC103), which had the same sequence with the prototype B95-8. Among 3 functional domains of BZLF1 protein, the transactivation domain had most mutations, followed by the bZIP domains (the DNA binding domain and dimerization domain). No prevalence of any subtypes or mutations in the functional domains among three specimen groups was found (P > 0.05). Our study indicates that BZLF1 subtypes and amino acid changes in functional domains are not preferentially associated with EBV-associated gastric carcinomas or nasopharyngeal carcinomas in Northern China. BZLF1 gene variations are geographically restricted rather than tumor-specific polymorphisms. [Copyright &y& Elsevier]