[Mechanism of DNA polymerase beta hyper-expression in malignant transformation induced by benzo[a] pyrene].

Objective: To explore the mechanism of the hyper-expression of DNA polymerase beta (polbeta) in benzo[a]pyrene (BaP) induced malignant transformed cell (polbeta-T).

Methods: The mutation of polbeta gene exon and promoter were examined using reverse transcriptase-polymerase chain reaction-single strand conformation polymorphism (RT-PCR-SSCP) and gene sequencing. The expression of protein-arginine N-methyhransferase 6 (PRMT6) mRNA and protein in polbeta-T cell and control cell (polbeta cell) were investigated by RT-PCR and Western blot.

Results: RT-PCR-SSCP and gene sequencing revealed that the hyper-expression of polbeta in polbeta-T cell was not associated with the mutation of polbeta gene exon while insert mutation (G) and point mutation (C-->A) were found located in the core region of polbeta gene promoter. Furthermore, the expression of PRMT6 mRNA and protein also increased in polbeta-T cell compared with control cell (P<0.05).

Conclusion: The enhancement of expression of polbeta in polbeta-T cell might be attributed to the mutations locating in polbeta gene promoter on transcription level of polbeta gene, and PRMT6 might also enhance the expression of polbeta in polbeta-T cell through relative epigenetic pathways.