Phosphorylation induces sequence-specific conformational switches in the RNA polymerase II C-terminal domain.
Phosphorylation induces sequence-specific conformational switches in the RNA polymerase II C-terminal domain.
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DOI：
10.1038/ncomms15233
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发表时间：
2017-05-12
影响因子：
16.6
通讯作者：
Showalter SA
中科院分区：
文献类型：
--
作者：
Gibbs EB;Lu F;Portz B;Fisher MJ;Medellin BP;Laremore TN;Zhang YJ;Gilmour DS;Showalter SA
RNA聚合酶II （Pol II）的羧基末端结构域（CTD）通过磷酸化状态循环，与转录周期的进展相关，并调节新生mRNA的加工。酵母和哺乳动物CTD的结构分析受到其重复序列的阻碍。在这里，我们确定了黑腹果蝇CTD的一个区域，该区域对体内Pol II功能至关重要，并利用其内部的自然序列变化来促进结构分析。质谱和核磁共振谱显示，超ser5磷酸化通过脯氨酸异构化改变了该区域的局部结构。该开关的序列上下文调节磷酸酶Ssu72的活性，导致特定七元体的优先去磷酸化。综上所述，环境依赖的构象开关和偏倚的去磷酸化提示了一种选择性募集顺式脯氨酸特异性调节因子和区域特异性调节CTD编码的机制，这可能会增强发育复杂生物体中的基因调控。RNA聚合酶II c端结构域作为协调转录和新生mRNA加工的枢纽。在这里，作者确定了在CTD七磷酸重复序列中脯氨酸反式到顺式异构化的磷酸化依赖开关，使这些重复序列容易受到调节酶的进一步修饰。
The carboxy-terminal domain (CTD) of the RNA polymerase II (Pol II) large subunit cycles through phosphorylation states that correlate with progression through the transcription cycle and regulate nascent mRNA processing. Structural analyses of yeast and mammalian CTD are hampered by their repetitive sequences. Here we identify a region of the Drosophila melanogaster CTD that is essential for Pol II function in vivo and capitalize on natural sequence variations within it to facilitate structural analysis. Mass spectrometry and NMR spectroscopy reveal that hyper-Ser5 phosphorylation transforms the local structure of this region via proline isomerization. The sequence context of this switch tunes the activity of the phosphatase Ssu72, leading to the preferential de-phosphorylation of specific heptads. Together, context-dependent conformational switches and biased dephosphorylation suggest a mechanism for the selective recruitment of cis-proline-specific regulatory factors and region-specific modulation of the CTD code that may augment gene regulation in developmentally complex organisms. The RNA polymerase II C-terminal domain acts as a hub to coordinate transcription and nascent mRNA processing. Here the authors identify a phosphorylation-dependent switch in the trans-to-cis isomerization of proline in the CTD heptad repeats that make those repeats susceptible to further modifications by regulatory enzymes.