Physical mapping of an origin of bidirectional replication at the centre of the Borrelia burgdorferi linear chromosome
Physical mapping of an origin of bidirectional replication at the centre of the Borrelia burgdorferi linear chromosome
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DOI：
10.1046/j.1365-2958.1999.01368.x
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发表时间：
1999-04-01
影响因子：
3.6
通讯作者：
Hinnebusch, BJ
中科院分区：
文献类型：
--
作者：
Picardeau, M;Lobry, JR;Hinnebusch, BJ
伯氏疏螺旋体染色体是线性的，端粒的特征在于末端反向重复序列和共价闭合的单链发夹环。这些不寻常分子的复制机制尚不清楚。以前的分析细菌染色体的完整序列已被确定，包括B，burgdorferi，揭示了一个突然的开关在极性的Co偏斜在已知的或假定的复制起点。我们使用新生DNA链分析来对B进行物理作图。Burgdorferi起源于线性染色体中心的2 kb区域内，并表明复制从该起源进行双向进行。结果是一致的复制模型，其中终止发生在端粒后，双向，对称延长从中央原点。在该螺旋体的起源处没有发现其他细菌染色体起源的典型序列。线性染色体的复制起点最可能的位置是dnaA和dnaN之间的240 bp序列，CG偏斜发生转换。
The Borrelia burgdorferi chromosome is linear, with telomeres characterized by terminal inverted repeats and covalently closed single-stranded hairpin loops. The replication mechanism of these unusual molecules is unknown. Previous analyses of bacterial chromosomes for which the complete sequence has been determined, including that of B, burgdorferi, revealed an abrupt switch in polarity of Co skew at known or putative origins of replication. We used nascent DNA strand analysis to physically map the B. burgdorferi origin to within a 2 kb region at the centre of the linear chromosome, and to show that replication proceeds bidirectionally from this origin. The results are consistent with replication models in which termination occurs at the telomeres after bidirectional, symmetrical elongation from the central origin. Sequences typical of origins of other bacterial chromosomes were not found at the origin of this spirochete. The most likely location of the replication origin of the linear chromosome is the 240 bp sequence between dnaA and dnaN where the switch in CG skew occurs.