5′端非翻译区对LT-B基因表达的影响

Effect of 5'non-coding Region on Expression of LT-B Gene

mRNA5＇端非翻译区的不同结构可影响基因表达,为了改善编码人毒素源性大肠杆菌热敏感肠毒素B亚单位的LT-B基因的表达水平,我们把该基因置于pBV220载体的P_RP_L串联启动子下游,构建了带有不同核苷酸组成的5＇端非翻译区的重组体。这些重组体分别在大肠杆菌HB101和DH5α中表达。结果表明,起始密码前有两个连续串联SD序列的LT-B基因的表达水平低于只有单个SD序列下的表达水平,而翻译偶联可使表达改善;用不同的SD序列LT-B基因的表达水平也有所不同,用基因本身SD序列可能要比用pBV220P_L启动子下游的SD序列好;在只含单个LT-B基因SD序列的重组体中,5＇端非翻译区序列的长短对LT-B基因表达没有什么影响;重组体在HB101中的表达水平高于在DH5α中的表达水平。

The different construction of mRNA 5' non-coding region may affect gene expression. In order to improve expression level, we constructed recombinant plasmids with different nucleotide composition of the 5' non-coding region which direct the synthesis of human toxicogenic E. coli heat-labile enterotoxin B subunit coded by LT-B gene under the control of the PRPL tandem promoter of vector pBV220. These recombi-nants were expressed in E. coli HB101 and DH5a, respectively. The results show that the expression levels of LT-B gene with two tandem SD sequences upstream from the initiation codon are lower than those with only one SD sequence and translation coupling can improve the expression levels; The different SD sequences can affect the expression of LT-B gene a little. The SD sequence of LT-B gene itself may be better for expression than that of the vector pBV220. The length of 5' non-coding region in the recombinants harboring only one SD sequence has no effect on the expression of LT-B gene. The expression of LT-B gene in HB101 is higher than that in DH5a.