Molecular genetic analysis of enediyne antibiotic biosynthesis genes

Dynemicin是一种具有蒽醌和烯二炔结构的独特杂化结构的烯二炔类抗肿瘤抗生素。为了阐明其生物合成机制，从产动力菌的放线菌chersina Micromonospora进行了ii型聚酮生物合成基因的克隆。通过actii探针筛选，从疟原虫基因组DNA文库中克隆出约20kb的片段。测定14.3 kb区域的核苷酸序列并进行开放阅读框（ORF）分析。在该区域共发现12个orf。数据库同源性检索表明，ORF2、4、5、6和8分别编码环化酶、β -酮酰合成酶、链长因子、辅酶a连接酶和酰基转移酶。因此，克隆的基因是典型的ii型聚酮合成酶基因簇，具有独特的orf，如加氧酶和额外的β -酮酰合成酶。进一步的分析正在进行中，以确定这个克隆的基因簇是否参与chersina的动力菌素生物合成。

Dynemicin is an enediyne antitumor antibiotic with unique hybrid structure of anthraquinone and enediyne structures. To elucidate its biosynthesis mechanism, cloning of type-II polyketide biosynthesis gene was carried out from Micromonospora chersina, a dynemicin producing actinomycete. By screening with actI probe, ca.20kb fragment was cloned from M.chersina genomic DNA library. The nucleotide sequence of 14.3 kb region was determined and open reading frame (ORF) analysis was carried out. In this region, 12 ORFs were found. Data base homology search indicated that ORF2,4,5,6 and 8 encode cyclase, beta-ketoacyl synthase, chain length factor, CoA-ligase and acyltransferase, respectively. Thus, the cloned gene consisted of typical type-II polyketide synthase gene cluster with unique ORFs such as oxygenases and addtitional beta-ketoacyl synthase. Further analysis is on the way to identify whether this cloned gene cluster is involved in dynemicin biosynthesis in M.chersina.