c-myc脱氧核酶对白血病细胞端粒酶活性的抑制作用

Inhibitory effect of c-myc DNAzyme on telomerase activity in human leukemia cells

目的：探讨c-myc脱氧核酶的切割作用及对白血病细胞端粒酶活性的影响.方法：合成针对c-myc mRNA的“10～23”型脱氧核酶DzMycI及其类似物DzMycI提取总RNA在细胞外切割c-myc mRNA;转染白血病细胞系HL-60后,用RT-PCR扩增c-myc基因片段和端粒酶蛋白亚基hTERT的片段,用PCR-ELISA法测定端粒酶活性.结果：脱氧核酶DzMycI在细胞外和细胞内均能够有效地切割c-myc mRNA;在转染HL-60后,DzMycI显著抑制白血病细胞生长（P〈0.05）,下调端粒酶蛋白亚基hTERT的表达,显著降低HL-60细胞端粒酶活性（P〈0.05）.DzMycI催化中心的一个碱基被替换后形成的脱氧寡核苷酸DzMycI在胞外和胞内均不表现对c-myc mRNA的切割作用.结论：脱氧核酶DzMycI确实能够高效特异地切割c-myc mRNA,降低白血病细胞端粒酶活性,抑制白血病细胞生长,有可能作为c-myc抑制剂用于白血病的基因治疗领域中.

AIM： To explore the cleavage of c-myc mRNA by a DNAzyme and its effect on telomerase activity in a hmnan leukemia cell line HL-60. METHODS： A ＂10-23＂ DNAzyme（ DzMycI） targeted against c-myc mRNA and its analogues （DzMycI＇） were synthesized and used to cleave c-myc mRNA. The cleaving efficiency and the expression of human telomerase reverse transcriptase （hTERT） was assessed by RT-PCR and telomerase activity was assayed by PCR-ELISA. RESULTS： DzMycI exhibited effective cleaving ability and after transfection into HL-60 cells, down-regulated the hTERT expression and telomerase activity （ P 〈 0.01 ）, and inhibited the growth of the cells （ P 〈 0.05 ）. DzMycI＇, which was derived from DzMycI with a base displacement in the conserved catalytic motif, did not exhibit notable clea- ving effect on c-myc mRNA either outside the cells or in cells. CONCLUSION： The synthesized DNAzyme DzMycI can cleave c-myc mRNA with effectiveness and specificity, decrease the telomerase activity and induce the apoptosis of HL-60 cells. As newly found c-myc inhibitors, DNAzymes will probably play an important role in the gene therapy of leukemia.