新生霉素敏感的拓扑异构酶在莱茵衣藻叶绿体DNA复制中的作用

Woelfle M A, Thompson R J, Mosig G

Department of Molecular Biology, Vanderbilt University, Nashville, TN 37235.

Nucleic Acids Res. 1993 Sep 11;21(18):4231-8. doi: 10.1093/nar/21.18.4231.

We have examined DNA replication in Chlamydomonas reinhardtii chloroplasts in vivo when chloroplast type II topoisomerases are inactivated with sublethal doses of novobiocin. DNA replication is at first inhibited under these conditions. However, after a delay of several hours, chloroplast chromosomes initiate a novobiocin-insensitive mode of DNA replication. This replication starts preferentially near a hotspot of recombination in the large inverted repeats, instead of from the normal chloroplast origins, oriA and oriB. It replicates one, but not the other single-copy region of the chloroplast chromosome. We speculate that novobiocin-insensitive DNA replication in chloroplasts requires recombination in this preferred initiation region.

我们已经研究了莱茵衣藻叶绿体在体内的DNA复制情况，此时叶绿体II型拓扑异构酶被亚致死剂量的新生霉素灭活。在这些条件下，DNA复制起初受到抑制。然而，经过数小时的延迟后，叶绿体染色体启动了一种对新生霉素不敏感的DNA复制模式。这种复制优先在大的反向重复序列中的一个重组热点附近开始，而不是从正常的叶绿体起源oriA和oriB开始。它复制叶绿体染色体的一个单拷贝区域，但不是另一个。我们推测，叶绿体中对新生霉素不敏感的DNA复制需要在这个优先起始区域进行重组。