The SOS response is readily triggered by replication fork stalling caused by DNA damage or a dysfunctional replicative apparatus in Escherichia coli cells. E. coli dinB encodes DinB DNA polymerase and its expression is upregulated during the SOS response. DinB catalyzes translesion DNA synthesis in place of a replicative DNA polymerase III that is stalled at a DNA lesion. We showed previously that DNA replication was suppressed without exogenous DNA damage in cells overproducing DinB. In this report, we confirm that this was due to a dose-dependent inhibition of ongoing replication forks by DinB. Interestingly, the DinB-overproducing cells did not significantly induce the SOS response even though DNA replication was perturbed. RecA protein is activated by forming a nucleoprotein filament with single-stranded DNA, which leads to the onset of the SOS response. In the DinB-overproducing cells, RecA was not activated to induce the SOS response. However, the SOS response was observed after heat-inducible activation in strain recA441 (encoding a temperature-sensitive RecA) and after replication blockage in strain dnaE486 (encoding a temperature-sensitive catalytic subunit of the replicative DNA polymerase III) at a non-permissive temperature when DinB was overproduced in these cells. Furthermore, since catalytically inactive DinB could avoid the SOS response to a DinB-promoted fork block, it is unlikely that overproduced DinB takes control of primer extension and thus limits single-stranded DNA. These observations suggest that DinB possesses a feature that suppresses DNA replication but does not abolish the cell's capacity to induce the SOS response. We conclude that DinB impedes replication fork progression in a way that does not activate RecA, in contrast to obstructive DNA lesions and dysfunctional replication machinery.

译文

:SOS响应很容易因DNA损伤或大肠杆菌细胞复制装置功能异常而引起的复制叉停转而触发。大肠杆菌dinB编码DinB DNA聚合酶,并且在SOS反应期间其表达上调。 DinB可以催化停滞在DNA病变处的复制型DNA聚合酶III,从而催化跨病变的DNA合成。我们以前表明,在过量生产DinB的细胞中,DNA复制被抑制而没有外源DNA损伤。在此报告中,我们确认这是由于DinB对正在进行的复制叉的剂量依赖性抑制。有趣的是,即使DNA复制受到干扰,DinB过量产生细胞也不会显着诱导SOS反应。 RecA蛋白通过形成具有单链DNA的核蛋白丝而被激活,从而导致SOS反应的发生。在过量产生DinB的细胞中,RecA没有被激活以诱导SOS反应。但是,在菌株recA441中的热诱导激活(编码温度敏感的RecA)之后和在菌株dnaE486中的复制受阻(编码复制性DNA聚合酶III的温度敏感催化亚基)非允许的情况下,观察到了SOS反应。 DinB在这些细胞中过量产生时的温度。此外,由于具有催化活性的DinB可以避免SOS对DinB促进的叉叉反应的应答,因此过量生产的DinB不太可能控制引物延伸并因此限制了单链DNA。这些观察结果表明,DinB具有抑制DNA复制但不会消除细胞诱导SOS反应的能力的功能。我们得出的结论是,与阻塞性DNA损伤和功能障碍的复制机制相反,DinB以不激活RecA的方式阻碍了复制叉的发展。

+1
+2
100研值 100研值 ¥99课程
检索文献一次
下载文献一次

去下载>

成功解锁2个技能,为你点赞

《SCI写作十大必备语法》
解决你的SCI语法难题!

技能熟练度+1

视频课《玩转文献检索》
让你成为检索达人!

恭喜完成新手挑战

手机微信扫一扫,添加好友领取

免费领《Endnote文献管理工具+教程》

微信扫码, 免费领取

手机登录

获取验证码
登录