The Human RNA Polymerase I Transcription Terminator Complex Acts as a Replication Fork Barrier That Coordinates the Progress of Replication with rRNA Transcription Activity
The Human RNA Polymerase I Transcription Terminator Complex Acts as a Replication Fork Barrier That Coordinates the Progress of Replication with rRNA Transcription Activity
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DOI：
10.1128/mcb.01521-14
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发表时间：
2015-05-01
影响因子：
5.3
通讯作者：
Kobayashi, Takehiko
中科院分区：
文献类型：
--
作者：
Akamatsu, Yufuko;Kobayashi, Takehiko
在S阶段，基因组DNA的复制和转录需要相互容纳，否则其机械碰撞，并且染色体不稳定性可能是可能的结果。在这里，我们表征了47S前RRNA基因（核糖体DNA [rDNA]）下游的人类复制叉屏障（RFB）。我们发现，最近端的转录终结器SAL Box T1充当极性RFB，而另一个SAL Box T4/T5则是双向逮捕复制叉的。这些位点的叉子列活动取决于聚合酶I（POL I）转录终止因子1（TTF-1）和一个重置组件，永恒（TIM）。我们还发现，RFB活性与rDNA副本相关，含甲基化的CpG，并与主动转录RRNA基因复制的时间相吻合。 RFB部位的叉式停滞失败导致叉子进展的放缓向相反的方向移动到rRNA转录。转录的化学抑制作用抵消了叉子的减速，表明在没有RFB活性的情况下，RRNA转录阻碍了复制。因此，我们的结果揭示了RFB在高度转录的rRNA基因中的复制和转录活性进展方面的作用。
In S phase, the replication and transcription of genomic DNA need to accommodate each other, otherwise their machineries collide, with chromosomal instability as a possible consequence. Here, we characterized the human replication fork barrier (RFB) that is present downstream from the 47S pre-rRNA gene (ribosomal DNA [rDNA]). We found that the most proximal transcription terminator, Sal box T1, acts as a polar RFB, while the other, Sal box T4/T5, arrests replication forks bidirectionally. The fork-arresting activity at these sites depends on polymerase I (Pol I) transcription termination factor 1 (TTF-1) and a replisome component, TIMELESS (TIM). We also found that the RFB activity was linked to rDNA copies with hypomethylated CpG and coincided with the time that actively transcribed rRNA genes are replicated. Failed fork arrest at RFB sites led to a slowdown of fork progression moving in the opposite direction to rRNA transcription. Chemical inhibition of transcription counteracted this deceleration of forks, indicating that rRNA transcription impedes replication in the absence of RFB activity. Thus, our results reveal a role of RFB for coordinating the progression of replication and transcription activity in highly transcribed rRNA genes.