Xu Mingxuan, Zhu Yingmin, Zhang Ran, Shen Meijuan, Jiang Weihong, Zhao Guoping, Qin Zhongjun
Shanghai Institute of Plant Physiology, Shanghai Institutes of Biological Sciences, The Chinese Academy of Sciences, 300 Fenglin Road, Shanghai, 200032 People's Republic of China.
J Bacteriol. 2006 Oct;188(19):6851-7. doi: 10.1128/JB.00873-06.
The nucleotide sequence of Streptomyces lividans linear plasmid SLP2 consists of 50,410 bp (C. H. Huang, C. Y. Chen, H. H. Tsai, C. Chen, Y. S. Lin, and C. W. Chen, Mol. Microbiol. 47:1563-1576, 2003). Here we report that the basic SLP2 locus for plasmid replication in circular mode resembles that of Streptomyces linear plasmids pSLA2 and SCP1 and comprises iterons(SLP2) and the adjacent rep(SLP2) gene. More efficient replication additionally required the 47-bp sequence between bp 581 and 628 upstream of the iterons. Replacement of either the iterons or the rep gene of SLP2 by the corresponding genes of pSLA2 or SCP1 still allows propagation in Streptomyces, although the transformation frequencies were 3 orders of magnitude lower than the original plasmids, suggesting that these plasmids share similar replication mechanisms. To replicate SLP2 in linear mode, additional SLP2 loci--either mtap(SLP2)/tpg(SLP2) or mtap(SLP2)/ilrA(SLP2)--were required. IlrA(SLP2) protein binds specifically to the iterons(SLP2) in vitro. Interactions were detected between these SLP2-borne replication proteins (Mtap(SLP2), Tpg(SLP2), and IlrA(SLP2)) and the telomeric replication proteins (TpgL, TapL, and TpgL) of the S. lividans chromosome, respectively, but the SLP2 proteins failed to interact. These results suggest that SLP2 recruits chromosomally encoded replication proteins for its telomere replication.
变铅青链霉菌线性质粒SLP2的核苷酸序列由50410个碱基对组成（C.H. Huang、C.Y. Chen、H.H. Tsai、C. Chen、Y.S. Lin和C.W. Chen，《分子微生物学》47:1563 - 1576，2003年）。在此我们报告，以环状模式进行质粒复制的基本SLP2基因座类似于链霉菌线性质粒pSLA2和SCP1的基因座，包括迭代子（SLP2）和相邻的rep（SLP2）基因。更高效的复制还需要迭代子上游第581至628碱基对之间的47碱基序列。用pSLA2或SCP1的相应基因替换SLP2的迭代子或rep基因仍可在链霉菌中繁殖，尽管转化频率比原始质粒低3个数量级，这表明这些质粒具有相似的复制机制。要以线性模式复制SLP2，则需要额外的SLP2基因座——要么是mtap（SLP2）/tpg（SLP2），要么是mtap（SLP2）/ilrA（SLP2）。IlrA（SLP2）蛋白在体外能特异性结合迭代子（SLP2）。分别检测到这些由SLP2携带的复制蛋白（Mtap（SLP2）、Tpg（SLP2）和IlrA（SLP2））与变铅青链霉菌染色体的端粒复制蛋白（TpgL、TapL和TpgL）之间的相互作用，但SLP2蛋白之间未能相互作用。这些结果表明，SLP2招募染色体编码的复制蛋白用于其端粒复制。
