- 學位論文
檳榔鹼透過表觀遺傳方式影響DDB2基因的表現
Arecoline-mediated epigenetic regulation of DDB2 expression
並列摘要
Arecoline is a genotoxic alkaloid found in areca nut. It inhibits nucleotide excision repair (NER) and DNA double-strand break repair pathways, thereby induces DNA damages. The Damage-Specific DNA Binding Protein 2 (DDB2) is critical for the initiation of NER pathway. Previously we found that arecoline inhibited DDB2 expression. However, the mechanism underlying the arecoline-mediated repression of DDB2 expression is unclear. We propose that arecoline regulates DDB2 expression through histone deacetylases (HDACs). In this study, we demonstrated that arecoline repressed DDB2 promoter activity as well as DDB2 mRNA expression in HEp-2 and HEK 293 cells, whereas the pan-HDAC inhibitors sodium butyrate and trichostatin A restored arecoline-mediated repression of DDB2. The class I HDAC-specific inhibitor CI-994 also rejuvenated the promoter activity and mRNA expression of DDB2 in arecoline-treated cells, suggesting that arecoline inhibited DDB2 expression through class I HDACs. Arecoline-mediated repression of gene expression through class I HDACs was verified by examining the promoter activity and mRNA expression of p21, a cyclin-dependent kinase inhibitor that is known to be regulated by class I HDACs. Real-time quantitative RT-PCR showed that HDAC1 mRNA level was 76% elevated in arecoline-treated HEp-2 cells. Arecoline did not induce mRNA expression of HDAC2 and HDAC3. However, overexpression of HDAC3, but not HDAC1, alone partially repressed DDB2 promoter activity. These results demonstrated that arecoline might regulate the network between class I HDAC members and transcriptional machineries, instead of affecting a single HDAC, to inhibit DDB2 expression.