Teixeira Daniela, Parker Roy
Department of Molecular and Cellular Biology and Howard Hughes Medical Institute, University of Arizona, Tucson, AZ 85721-0106, USA.
Mol Biol Cell. 2007 Jun;18(6):2274-87. doi: 10.1091/mbc.e07-03-0199. Epub 2007 Apr 11.
Recent experiments have defined cytoplasmic foci, referred to as processing bodies (P-bodies), that contain untranslating mRNAs in conjunction with proteins involved in translation repression and mRNA decapping and degradation. However, the order of protein assembly into P-bodies and the interactions that promote P-body assembly are unknown. To gain insight into how yeast P-bodies assemble, we examined the P-body accumulation of Dcp1p, Dcp2p, Edc3p, Dhh1p, Pat1p, Lsm1p, Xrn1p, Ccr4p, and Pop2p in deletion mutants lacking one or more P-body component. These experiments revealed that Dcp2p and Pat1p are required for recruitment of Dcp1p and of the Lsm1-7p complex to P-bodies, respectively. We also demonstrate that P-body assembly is redundant and no single known component of P-bodies is required for P-body assembly, although both Dcp2p and Pat1p contribute to P-body assembly. In addition, our results indicate that Pat1p can be a nuclear-cytoplasmic shuttling protein and acts early in P-body assembly. In contrast, the Lsm1-7p complex appears to primarily function in a rate limiting step after P-body assembly in triggering decapping. Taken together, these results provide insight both into the function of individual proteins involved in mRNA degradation and the mechanisms by which yeast P-bodies assemble.
最近的实验确定了细胞质聚集体，即加工小体（P小体），其包含未翻译的mRNA以及参与翻译抑制、mRNA脱帽和降解的蛋白质。然而，蛋白质组装到P小体中的顺序以及促进P小体组装的相互作用尚不清楚。为了深入了解酵母P小体是如何组装的，我们研究了在缺失一种或多种P小体成分的缺失突变体中Dcp1p、Dcp2p、Edc3p、Dhh1p、Pat1p、Lsm1p、Xrn1p、Ccr4p和Pop2p在P小体中的积累情况。这些实验表明，Dcp2p和Pat1p分别是将Dcp1p和Lsm1-7p复合物招募到P小体所必需的。我们还证明P小体组装是冗余的，虽然Dcp2p和Pat1p都有助于P小体组装，但P小体组装不需要任何单个已知的P小体成分。此外，我们的结果表明，Pat1p可以是一种核质穿梭蛋白，并在P小体组装的早期起作用。相比之下，Lsm1-7p复合物似乎主要在P小体组装后的限速步骤中发挥作用，触发脱帽。综上所述，这些结果为参与mRNA降解的单个蛋白质的功能以及酵母P小体的组装机制提供了深入了解。
