Park K, Han E, Paulsson J, Chattoraj D K
Laboratory of Biochemistry, NCI, NIH, Bethesda, MD 20892-4255, USA.
EMBO J. 2001 Dec 17;20(24):7323-32. doi: 10.1093/emboj/20.24.7323.
In one family of bacterial plasmids, multiple initiator binding sites, called iterons, are used for initiation of plasmid replication as well as for the control of plasmid copy number. Iterons can also pair in vitro via the bound initiators. This pairing, called handcuffing, has been suggested to cause steric hindrance to initiation and thereby control the copy number. To test this hypothesis, we have compared copy numbers of isogenic miniP1 plasmid monomer and dimer. The dimer copy number was only one-quarter that of the monomer, suggesting that the higher local concentration of origins in the dimer facilitated their pairing. Physical evidence consistent with iteron-mediated pairing of origins preferentially in the dimer was obtained in vivo. Thus, origin handcuffing can be a mechanism to control P1 plasmid replication.
在一类细菌质粒中,多个起始子结合位点,即所谓的迭代子,用于启动质粒复制以及控制质粒拷贝数。迭代子在体外也可通过结合的起始子进行配对。这种配对,称为“手铐式”配对,被认为会对起始过程造成空间位阻,从而控制拷贝数。为了验证这一假设,我们比较了同基因miniP1质粒单体和二聚体的拷贝数。二聚体的拷贝数仅为单体的四分之一,这表明二聚体中起始点的局部浓度较高,有利于它们的配对。在体内获得了与迭代子介导的起始点优先在二聚体中配对相一致的物理证据。因此,起始点“手铐式”配对可能是一种控制P1质粒复制的机制。