Variation and Functional Study of Q Promotor of Epstein-Barr Virus in Nasopharyngeal Carcinoma / 中山大学学报(医学科学版)

ABSTRACT

[Objective] To investigate the variation of Q promoter (Qp) in nasopharyngeal carcinoma (NPC) cells, and to compare the existing two mutant sites [62 225 site(g→a)and 62 422 site (g→c) ] Qp in NPC cells with the Qp in B95.8 cell line in the functional and biological difference. [Methods] The Qp sequence was amplified in the samples from 29 cases of paraffin-embedded tissues of NPC suffers and 14 cases of peripheral blood of healthy adults by polymerase chain reaction (PCR) method (totally 43 cases). The point mutations on specified sites were analyzed and statistically compared from sequencing results. The sequences of variant and prototype Qp were amplified by PCR and cloned into luciferase reporter vector (pGL3-basic), then transfected into HaCat cells respectively. The transcriptional activity was compared between variant and prototype Qp using luciferase reporter system. The DNA binding affinity of mutant and prototype Qp to Sp1 was compared through chromatin immunoprecipitation (CHIP) method since mutation of nt 62 225 located in a Spl binding site. [Results] The mutation rate of Qp was significantly higher in NPC compared with healthy controls (P=0.039 5, <0.05), which suggested the variant Qp was closely associated with NPC. The transcription of the luciferase gene promoted by variant Qp was significant more than that of prototype Qp in transient transfection assay (2.51, P<0.05). The binding affinity of variant Qp to Sp1 was about 1.52 times higher than that of prototype Qp as determined by quantitative ChIP assay. [Conclusions] The transcriptional activity was enhanced in variant Qp in NPC cells compared with prototype, which possibly through the higher binding affinity to Sp1. We suggest that the mutated Qp may play an important role during the EBV infection and transformation of nasopharyngeal epithelium.