Okada Chimari, Yamashita Eiki, Lee Soo Jae, Shibata Satoshi, Katahira Jun, Nakagawa Atsushi, Yoneda Yoshihiro, Tsukihara Tomitake
Institute for Protein Research, Osaka University, 3-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
Science. 2009 Nov 27;326(5957):1275-9. doi: 10.1126/science.1178705.
Nuclear export of microRNAs (miRNAs) by exportin-5 (Exp-5) is an essential step in miRNA biogenesis. Here, we present the 2.9 angstrom structure of the pre-miRNA nuclear export machinery formed by pre-miRNA complexed with Exp-5 and a guanine triphosphate (GTP)-bound form of the small nuclear guanine triphosphatase (GTPase) Ran (RanGTP). The x-ray structure shows that Exp-5:RanGTP recognizes the 2-nucleotide 3' overhang structure and the double-stranded stem of the pre-miRNA. Exp-5:RanGTP shields the pre-miRNA stem from degradation in a baseball mitt-like structure where it is held by broadly distributed weak interactions, whereas a tunnel-like structure of Exp-5 interacts strongly with the 2-nucleotide 3' overhang through hydrogen bonds and ionic interactions. RNA recognition by Exp-5:RanGTP does not depend on RNA sequence, implying that Exp-5:RanGTP can recognize a variety of pre-miRNAs.
微小RNA（miRNA）通过输出蛋白5（Exp-5）进行核输出是miRNA生物合成中的关键步骤。在此，我们展示了由前体miRNA与Exp-5以及结合鸟嘌呤三磷酸（GTP）的小核鸟嘌呤三磷酸酶（GTP酶）Ran（RanGTP）形成的前体miRNA核输出机制的2.9埃结构。X射线结构表明，Exp-5:RanGTP识别前体miRNA的2个核苷酸的3'突出端结构和双链茎。Exp-5:RanGTP以类似棒球手套的结构保护前体miRNA茎免受降解，在前体miRNA茎中，它通过广泛分布的弱相互作用固定，而Exp-5的隧道样结构通过氢键和离子相互作用与2个核苷酸的3'突出端强烈相互作用。Exp-5:RanGTP对RNA的识别不依赖于RNA序列，这意味着Exp-5:RanGTP可以识别多种前体miRNA。
