Brasch M A, Cohen S N
Department of Genetics, Stanford University School of Medicine, California 94305, USA.
Plasmid. 1995 May;33(3):191-7. doi: 10.1006/plas.1995.1020.
A 2.1-kb SacII DNA fragment of the high-copy-number Streptomyces lividans plasmid pIJ101 previously has been shown to include the functions required for maintenance of pIJ101 as an extrachromosomal replicon. This fragment contains the open translational reading frames rep and orf 56 plus an intervening segment believed to be noncoding. Using deletion mutations, we show that the pIJ101 replication origin and other cis-acting sites necessary and sufficient for replication map to a DNA segment that extends 515 bp 5' to the translational start of Rep and lacks orf56. Plasmids that include this segment are maintained in S. lividans as extrachromosomal replicons when complemented in trans by the rep gene product.
先前已表明，高拷贝数的天蓝色链霉菌质粒pIJ101的一个2.1 kb SacII DNA片段包含将pIJ101作为染色体外复制子进行维持所需的功能。该片段包含开放阅读框rep和orf 56，以及一个被认为是非编码的中间区段。通过缺失突变，我们发现pIJ101复制起点以及复制所必需且足够的其他顺式作用位点定位于一个DNA区段，该区段从Rep翻译起始位点的5'端延伸515 bp，且不包含orf56。当由rep基因产物进行反式互补时，包含该区段的质粒在天蓝色链霉菌中作为染色体外复制子得以维持。
