Kimmel Center for Biology and Medicine at the Skirball Institute, New York University School of Medicine, New York, NY 10016.
Department of Microbiology, New York University School of Medicine, New York, NY 10016.
Proc Natl Acad Sci U S A. 2020 Feb 18;117(7):3560-3567. doi: 10.1073/pnas.1914229117. Epub 2020 Feb 4.
Stresses that increase the cellular concentration of dinucleoside tetraphosphates (NpNs) have recently been shown to impact RNA degradation by inducing nucleoside tetraphosphate (Np) capping of bacterial transcripts. However, neither the mechanism by which such caps are acquired nor the function of NpNs in bacteria is known. Here we report that promoter sequence changes upstream of the site of transcription initiation similarly affect both the efficiency with which RNA polymerase incorporates dinucleoside polyphosphates at the 5' end of nascent transcripts in vitro and the percentage of transcripts that are Np-capped in , clear evidence for Np cap acquisition by NpN incorporation during transcription initiation in bacterial cells. RNA polymerase initiates transcription more efficiently with NpAs than with ATP, particularly when the coding strand nucleotide that immediately precedes the initiation site is a purine. Together, these findings indicate that NpNs function in bacteria as precursors to Np caps and that RNA polymerase has evolved a predilection for synthesizing capped RNA whenever such precursors are abundant.
强调指出，最近的研究表明，增加二核苷酸四磷酸（NpNs）的细胞浓度会通过诱导细菌转录物的核苷四磷酸（Np）加帽来影响 RNA 降解。然而，尚不清楚这些帽子是如何获得的，也不知道 NpNs 在细菌中的功能。在这里，我们报告说，转录起始位点上游的启动子序列变化同样会影响体外 RNA 聚合酶在新生转录本 5' 端掺入二核苷酸多磷酸的效率，以及被 Np 加帽的转录本的百分比，这清楚地表明 NpN 的掺入在细菌细胞中的转录起始过程中获得了 Np 帽。RNA 聚合酶以 NpAs 起始转录的效率高于以 ATP 起始转录的效率，特别是当起始位点前紧邻的编码链核苷酸是嘌呤时。这些发现共同表明，NpNs 在细菌中作为 Np 帽的前体发挥作用，并且 RNA 聚合酶在丰富此类前体时进化出了合成加帽 RNA 的倾向。
