Lin C T, Lyu Y L, Liu L F
Department of Pharmacology, UMDNJ-Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA.
Nucleic Acids Res. 1997 Aug 1;25(15):3009-16. doi: 10.1093/nar/25.15.3009.
Small inverted repeats (small palindromes) on plasmids have been shown to mediate a recombinational rearrangement event in Escherichia coli leading to the formation of inverted dimers (giant palindromes). This recombinational rearrangement event is efficient and independent of RecA and RecBCD. In this report, we propose a cruciform-dumbbell model to explain the inverted dimer formation mediated by inverted repeats. In this model, the inverted repeats promote the formation of a DNA cruciform which is processed by an endonuclease into a linear DNA with two hairpin loops at its ends. Upon DNA replication, this linear dumbbell-like DNA is then converted to the inverted dimer. In support of this model, linear dumbbell DNA molecules with unidirectional origin of DNA replication (ColE1 ori ) have been constructed and shown to transform E.coli efficiently resulting in the formation of the inverted dimer. The ability of linear dumbbell DNA to transform E.coli suggests that the terminal loops may be important in bypassing the requirement of DNA supercoiling for initiation of replication of the ColE1 ori.
质粒上的小反向重复序列（小回文序列）已被证明能介导大肠杆菌中的一种重组重排事件，导致反向二聚体（巨大回文序列）的形成。这种重组重排事件高效且独立于RecA和RecBCD。在本报告中，我们提出了一个十字形 - 哑铃模型来解释由反向重复序列介导的反向二聚体形成。在这个模型中，反向重复序列促进DNA十字形的形成，该十字形被一种内切核酸酶加工成两端带有两个发夹环的线性DNA。在DNA复制时，这种线性哑铃状DNA随后被转化为反向二聚体。为支持该模型，已构建了具有单向DNA复制起点（ColE1 ori）的线性哑铃状DNA分子，并证明其能高效转化大肠杆菌，导致反向二聚体的形成。线性哑铃状DNA转化大肠杆菌的能力表明，末端环在绕过DNA超螺旋对ColE1 ori复制起始的需求方面可能很重要。
