大肠杆菌甲基转移酶dcm基因的表达对变铅青链霉菌的多效性影响

Pleiotropic effects on Streptomyces lividans growth by Dcm expression

【目的】大肠杆菌的dcm基因编码的DNA甲基转移酶可以特异性地将5′CCWGG3′(W=A/T)序列中第二个胞嘧啶变成5-甲基胞嘧啶。Dcm甲基转移酶发现已有37年了,但其确切的功能不明,本篇主要研究其对变铅青链霉菌的影响。【方法】通过构建克隆、接合转移、异源表达及HPLC、酶切、Southern杂交等方法研究dcm基因的表达对变铅青链霉菌的多效性影响。【结果】首次发现变铅青链霉菌基因组中不含5-甲基胞嘧啶修饰,将dcm基因导入变铅青链霉菌后,接合子菌落比正常菌落小很多,并有放线紫红素产生。【结论】基因组的表观遗传修饰能激活沉默放线紫红素基因簇的表达这一现象,为基因组挖掘隐藏的活性天然产物提供了一条新途径。

[Objective] In Escherichia coli, cytosine DNA methylation occurring at the inner cytosine in the sequence 5′CCWGG3′, is catalyzed by the DNA cytosine methyltransferase（Dcm） protein.Although dcm modification has been studied for nearly 37 years, the biological role for this gene is still unclear. In this study, we focus on the function of dcm in Streptomyces lividans. [Methods] dcm gene was isolated from E. coli and introduced into S. lividans 1326; HPLC-MS, methylation sensitivity assay and Southern blot are used to study the expression of dcm in S. lividans. [Results]The colony of dcm-containing exoconjugant is much smaller than wild type, and the production of actinorhodin in either MS agar plate or R5 liquid media was enhanced by two folds. [Conclusion]Epigenetic modification of the gonome of S. lividans by Dcm can activate the actinordin biosynthesis, providing an alternative way for genomic mining of cryptic bioactive metabolites.