Dynamic interactions between the RNA chaperone Hfq, small regulatory RNAs, and mRNAs in live bacterial cells.
Dynamic interactions between the RNA chaperone Hfq, small regulatory RNAs, and mRNAs in live bacterial cells.
复制标题
作者：
Park S;Prévost K;Heideman EM;Carrier MC;Azam MS;Reyer MA;Liu W;Massé E;Fei J
RNA结合蛋白在调节RNAs和RNA介导的功能中发挥着多种作用。在细菌中，RNA伴侣Hfq是一种重要的转录后基因调节因子。使用活细胞超分辨率成像，我们可以区分Hfq与不同大小的细胞RNA的结合。我们证明，在正常生长条件下，Hfq表现出广泛的mRNA结合活性，其中Hfq的远端面在体内对mRNA结合起主要作用。此外，sRNAs既可以与Hfq以三元复合体的形式共同占据Hfq，也可以以一种结合面依赖的方式取代Hfq上的mRNA，这表明sRNAs快速进入Hfq以诱导sRNA介导的基因调控的机制。最后，我们的数据表明，HfQ通过其远端面与某些mRNAs结合可以招募RNase E以一种不依赖于SRNA的方式促进这些mRNAs的周转，并且HfQ的这种调节功能可以被在远端面强烈结合的sRNA竞争者所诱骗。信使RNAs或mRNAs是细胞用来传递存储在细胞DNA中的信息的分子，这样它就可以用来制造蛋白质。细菌可以调节它们的mRNA分子的水平，因此它们可以通过产生一种不同类型的RNA来控制蛋白质的合成，这种RNA被称为小调节RNA或sRNAs。每个sRNA可以与几个特定的mRNA靶点结合，并通过一种名为RNase E的酶来降解它们。某些细菌RNA结合蛋白，如Hfq，可以保护sRNA不被降解，并帮助它们找到它们的mRNA靶点。Hfq富含细菌。它对细菌在恶劣条件下的生长至关重要，并参与了病原菌感染细胞的过程。然而，它的数量超过了细胞中许多不同的RNA分子，这些分子竞争与蛋白质的结合。目前尚不清楚HfQ如何区分不同的RNAs的优先顺序，也不清楚HfQ与Hfq的结合如何改变RNA调控。Park、Prévost等人。对活细菌细胞进行成像，看看Hfq如何与不同大小的RNA链结合。实验表明，当细菌正常生长时，Hfq主要与mRNA分子结合，它可以招募RNase E来加速mRNA的降解，而不需要sRNA。Park、Prévost等人。还表明，sRNA可以通过取代结合的mRNA或与其共同结合来与HfQ结合。强结合Hfq的sRNA分子可以与mRNA竞争结合，从而减缓某些mRNAs的降解。Hfq可能成为治疗细菌感染的潜在药物靶点。了解它是如何与细菌中的其他分子相互作用的，可以为开发新的疗法提供帮助。这些发现表明，设计的与HfQ强烈结合的RNA可能会扰乱其在细菌中的调节作用，杀死它们。这可能是一个可行的药物设计机会，以对抗抗生素耐药性细菌的出现。
RNA-binding proteins play myriad roles in regulating RNAs and RNA-mediated functions. In bacteria, the RNA chaperone Hfq is an important post-transcriptional gene regulator. Using live-cell super-resolution imaging, we can distinguish Hfq binding to different sizes of cellular RNAs. We demonstrate that under normal growth conditions, Hfq exhibits widespread mRNA-binding activity, with the distal face of Hfq contributing mostly to the mRNA binding in vivo. In addition, sRNAs can either co-occupy Hfq with the mRNA as a ternary complex, or displace the mRNA from Hfq in a binding face-dependent manner, suggesting mechanisms through which sRNAs rapidly access Hfq to induce sRNA-mediated gene regulation. Finally, our data suggest that binding of Hfq to certain mRNAs through its distal face can recruit RNase E to promote turnover of these mRNAs in a sRNA-independent manner, and such regulatory function of Hfq can be decoyed by sRNA competitors that bind strongly at the distal face. Messenger RNAs or mRNAs are molecules that the cell uses to transfer the information stored in the cell’s DNA so it can be used to make proteins. Bacteria can regulate their levels of mRNA molecules, and they can therefore control how many proteins are being made, by producing a different type of RNA called small regulatory RNAs or sRNAs. Each sRNA can bind to several specific mRNA targets, and lead to their degradation by an enzyme called RNase E. Certain bacterial RNA-binding proteins, such as Hfq, protect sRNAs from being degraded, and help them find their mRNA targets. Hfq is abundant in bacteria. It is critical for bacterial growth under harsh conditions and it is involved in the process through which pathogenic bacteria infect cells. However, it is outnumbered by the many different RNA molecules in the cell, which compete for binding to the protein. It is not clear how Hfq prioritizes the different RNAs, or how binding to Hfq alters RNA regulation. Park, Prévost et al. imaged live bacterial cells to see how Hfq binds to RNA strands of different sizes. The experiments revealed that, when bacteria are growing normally, Hfq is mainly bound to mRNA molecules, and it can recruit RNase E to speed up mRNA degradation without the need for sRNAs. Park, Prévost et al. also showed that sRNAs could bind to Hfq by either replacing the bound mRNA or co-binding alongside it. The sRNA molecules that strongly bind Hfq can compete against mRNA for binding, and thus slow down the degradation of certain mRNAs. Hfq could be a potential drug target for treating bacterial infections. Understanding how it interacts with other molecules in bacteria could provide help in the development of new therapeutics. These findings suggest that a designed RNA that binds strongly to Hfq could disrupt its regulatory roles in bacteria, killing them. This could be a feasible drug design opportunity to counter the emergence of antibiotic-resistant bacteria.