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目的：探讨膀胱癌多药耐药性逆转的新方法。方法：应用计算机对mdrlmRNA二级结构进行模拟，设计针对mdrlmRNA1959位GUC的“锤头状”（Hammerhead）核酶（Ribozyme1，RZ1）基因，定点克隆于质粒pGEMEX-1的BamHⅠ和EcoRⅠ位点上；将mdrlcDNA864bp的片段亚克隆于pGEMEX-1的HindⅢ和EcoRⅠ位点上，mdrlcDNA1383bp片段亚克隆于pGEMEX-1的EcoRⅠ位点上，在T3启动子作用下体外转录成RZ1、864nt和1430nt的mdrlmRNA。结果：RZ1在体外分别将864nt和I430nt的mdrlmRNA切割成两个片段，切割温度在42℃和52℃两个条件下切割效率差异不明显。结论：核酶对底物的体外切割活性取决于核酶切割位点的选择，与底物长度无关。
Objective: To explore a new method of reversal of multidrug resistance in bladder cancer. Methods: The mdrlmRNA secondary structure was simulated by computer and the Hammerhead ribozyme (Ribozyme1, RZ1) gene targeting GUC at position 1959 of mdrlmRNA was designed and cloned into BamHI and EcoRI sites of plasmid pGEMEX-1. The mdrlcDNA864bp fragment was subcloned into the HindIII and EcoRI sites of pGEMEX-1. The mdrlcDNA1383bp fragment was subcloned into EcoRI site of pGEMEX-1 and transcribed into RZ1, 864nt and 1430nt mdrl mRNA in vitro under the action of T3 promoter. Results: RZ1 mdrlmRNA of 864nt and I430nt were cut into two fragments in vitro. The results showed that the cutting efficiency of RZ1 was not obvious at 42 ℃ and 52 ℃. CONCLUSION: The in vitro cleavage activity of ribozymes on substrates depends on the choice of ribozyme cleavage site, regardless of substrate length.