Chang A C, Slade M B, Williams K L
School of Biological Sciences, Macquarie University, Sydney, New South Wales, Australia.
Plasmid. 1990 Nov;24(3):208-17. doi: 10.1016/0147-619x(90)90004-v.
Ddp2 is a 5.8-kb, high-copy-number, nuclear plasmid found in the eukaryote Dictyostelium discoideum. We have identified two functional domains, a large open reading frame (Rep gene) and a 626-bp fragment containing an origin of replication (ori). The ori, when cloned into a shuttle vector, confers stable extrachromosomal replication in D. discoideum, provided that the Rep gene, which acts in trans, is integrated into the host genome. Ddp2 carries a 501-bp imperfect inverted repeat, and part of the ori overlaps with one of these repeats. The ori sequence contains two direct repeats of 49 bp comprising two 10-bp "TGTCATGACA" palindromes separated by a poly(T.A) sequence. Deletion of either 49-bp repeat abolished extrachromosomal replication.
Ddp2是一种在真核生物盘基网柄菌中发现的5.8千碱基对的高拷贝数核质粒。我们已经鉴定出两个功能结构域，一个大的开放阅读框（Rep基因）和一个包含复制起点（ori）的626碱基对片段。当ori被克隆到穿梭载体中时，只要反式作用的Rep基因整合到宿主基因组中，就能在盘基网柄菌中赋予稳定的染色体外复制。Ddp2带有一个501碱基对的不完全反向重复序列，ori的一部分与其中一个重复序列重叠。ori序列包含两个49碱基对的直接重复序列，由一个聚（T.A）序列隔开，包含两个10碱基对的“TGTCATGACA”回文序列。删除任何一个49碱基对的重复序列都会消除染色体外复制。
