Deshmukh Mandar V, Jones Brittnee N, Quang-Dang Duc-Uy, Flinders Jeremy, Floor Stephen N, Kim Candice, Jemielity Jacek, Kalek Marcin, Darzynkiewicz Edward, Gross John D
Department of Pharmaceutical Chemistry, University of California, San Francisco, 600 16th Street, San Francisco, CA 94107, USA.
Mol Cell. 2008 Feb 15;29(3):324-36. doi: 10.1016/j.molcel.2007.11.027.
Cap hydrolysis by Dcp2 is a critical step in several eukaryotic mRNA decay pathways. Processing requires access to cap-proximal nucleotides and the coordinated assembly of a decapping mRNP, but the mechanism of substrate recognition and regulation by protein interactions have remained elusive. Using NMR spectroscopy and kinetic analyses, we show that yeast Dcp2 resolves interactions with the cap and RNA body using a bipartite surface that forms a channel intersecting the catalytic and regulatory Dcp1-binding domains. The interaction with cap is weak but specific and requires binding of the RNA body to a dynamic interface. The catalytic step is stimulated by Dcp1 and its interaction domain, likely through a substrate-induced conformational change. Thus, activation of the decapping mRNP is restricted by access to 5'-proximal nucleotides, a feature that could act as a checkpoint in mRNA metabolism.
Dcp2介导的帽水解是几种真核生物mRNA降解途径中的关键步骤。该过程需要接近帽近端核苷酸并协调组装去帽mRNA核糖核蛋白（mRNP），但底物识别机制以及蛋白质相互作用的调控机制仍不清楚。通过核磁共振光谱和动力学分析，我们发现酵母Dcp2利用一个二分表面来解决与帽和RNA主体的相互作用，该表面形成了一个与催化和调节性Dcp1结合域相交的通道。与帽的相互作用较弱但具有特异性，并且需要RNA主体与动态界面结合。催化步骤受到Dcp1及其相互作用结构域的刺激，可能是通过底物诱导的构象变化。因此，去帽mRNP的激活受到5'-近端核苷酸可及性的限制，这一特征可能在mRNA代谢中起到检查点的作用。
