Artsimovitch I, Landick R
Department of Bacteriology, University of Wisconsin, Madison, WI 53706, USA.
Proc Natl Acad Sci U S A. 2000 Jun 20;97(13):7090-5. doi: 10.1073/pnas.97.13.7090.
Transcript elongation by RNA polymerase is discontinuous and interrupted by pauses that play key regulatory roles. We show here that two different classes of pause signals punctuate elongation. Class I pauses, discovered in enteric bacteria, depend on interaction of a nascent RNA structure with RNA polymerase to displace the 3' OH away from the catalytic center. Class II pauses, which may predominate in eukaryotes, cause RNA polymerase to slide backwards along DNA and RNA and to occlude the active site with nascent RNA. These pauses differ in their responses to antisense oligonucleotides, pyrophosphate, GreA, and general elongation factors NusA and NusG. In contrast, substitutions in RNA polymerase that increase or decrease the rate of RNA synthesis affect both pause classes similarly. We propose that both pause classes, as well as arrest and termination, arise from a common intermediate that itself binds NTP substrate weakly.
RNA聚合酶介导的转录延伸是不连续的，会被发挥关键调控作用的暂停所打断。我们在此表明，两类不同的暂停信号间断了延伸过程。在肠道细菌中发现的I类暂停，依赖新生RNA结构与RNA聚合酶的相互作用，将3'羟基从催化中心移开。II类暂停可能在真核生物中占主导，会使RNA聚合酶沿DNA和RNA向后滑动，并用新生RNA封闭活性位点。这些暂停对反义寡核苷酸、焦磷酸、GreA以及一般延伸因子NusA和NusG的反应有所不同。相比之下，RNA聚合酶中增加或降低RNA合成速率的替换对两类暂停的影响相似。我们提出，两类暂停以及停滞和终止均源于一个共同的中间体，该中间体自身与NTP底物的结合较弱。
