Mechanisms of backtrack recovery by RNA polymerases I and II
Mechanisms of backtrack recovery by RNA polymerases I and II
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RNA 聚合酶 I 和 II 的回溯恢复机制
DOI：
10.1073/pnas.1517011113
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发表时间：
2016-03-15
影响因子：
11.1
通讯作者：
Grill, Stephan W.
中科院分区：
文献类型：
--
作者：
Lisica, Ana;Engel, Christoph;Grill, Stephan W.
在DNA转录过程中，RNA聚合酶通常采取无活性的回溯状态。从回溯的恢复可以通过回溯RNA的一维扩散或切割发生，但聚合酶如何做出这种选择是未知的。在这里，我们使用单分子光镊实验和随机理论表明，选择的回溯恢复机制是由一维扩散和RNA切割之间的动力学竞争。值得注意的是，RNA聚合酶I（Pol I）和Pol II通过1D扩散从浅的回溯中恢复，使用RNA切割从中间深度恢复，并且不能从广泛的回溯中恢复。此外，Pol I和Pol II使用不同的机制来避免不可恢复的回溯。Pol I受到其亚基A12.2的保护，这降低了1D扩散的速率，并使转录物切割高达20 nt。相反，Pol II通过与切割刺激因子TFIIS结合而得到完全保护，这使得能够通过RNA切割从任何深度快速恢复。两者合计，我们确定不同的回溯恢复策略的Pol I和Pol II，阐明这些关键酶的细胞功能的演变。
During DNA transcription, RNA polymerases often adopt inactive backtracked states. Recovery from backtracks can occur by 1D diffusion or cleavage of backtracked RNA, but how polymerases make this choice is unknown. Here, we use single-molecule optical tweezers experiments and stochastic theory to show that the choice of a backtrack recovery mechanism is determined by a kinetic competition between 1D diffusion and RNA cleavage. Notably, RNA polymerase I (Pol I) and Pol II recover from shallow backtracks by 1D diffusion, use RNA cleavage to recover from intermediary depths, and are unable to recover from extensive backtracks. Furthermore, Pol I and Pol II use distinct mechanisms to avoid nonrecoverable backtracking. Pol I is protected by its subunit A12.2, which decreases the rate of 1D diffusion and enables transcript cleavage up to 20 nt. In contrast, Pol II is fully protected through association with the cleavage stimulatory factor TFIIS, which enables rapid recovery from any depth by RNA cleavage. Taken together, we identify distinct backtrack recovery strategies of Pol I and Pol II, shedding light on the evolution of cellular functions of these key enzymes.