CNRS, Centre de Génétique Moléculaire, FRE 3144, Gif-sur-Yvette, France.
EMBO J. 2010 Jan 6;29(1):145-57. doi: 10.1038/emboj.2009.308. Epub 2009 Oct 22.
How living cells deal with head-on collisions of the replication and transcription complexes has been debated for a long time. Even in the widely studied model bacteria Escherichia coli, the enzymes that take care of such collisions are still unknown. We report here that in vivo, the DinG, Rep and UvrD helicases are essential for efficient replication across highly transcribed regions. We show that when rRNA operons (rrn) are inverted to face replication, the viability of the dinG mutant is affected and over-expression of RNase H rescues the growth defect, showing that DinG acts in vivo to remove R-loops. In addition, DinG, Rep and UvrD exert a common function, which requires the presence of two of these three helicases. After replication blockage by an inverted rrn, Rep in conjunction with DinG or UvrD removes RNA polymerase, a task that is fulfilled in its absence by the SOS-induced DinG and UvrD helicases. Finally, Rep and UvrD also act at inverted sequences other than rrn, and promote replication through highly transcribed regions in wild-type E. coli.
长期以来，人们一直在争论活细胞如何应对复制和转录复合物的正面碰撞。即使在广泛研究的模式细菌大肠杆菌中，负责处理此类碰撞的酶仍然未知。我们在这里报告，在体内，DinG、Rep 和 UvrD 解旋酶对于在高度转录区域进行有效的复制是必不可少的。我们表明，当 rRNA 操纵子（rrn）倒置以面对复制时，dinG 突变体的存活率受到影响，并且 RNase H 的过表达可挽救生长缺陷，表明 DinG 在体内起作用以去除 R 环。此外，DinG、Rep 和 UvrD 发挥共同的功能，这需要这三种解旋酶中的两种存在。在 rrn 倒置引起复制受阻后，Rep 与 DinG 或 UvrD 一起去除 RNA 聚合酶，如果没有 SOS 诱导的 DinG 和 UvrD 解旋酶，该任务就无法完成。最后，Rep 和 UvrD 也在 rrn 以外的其他倒置序列中起作用，并促进野生型大肠杆菌中高度转录区域的复制。
