Luke Brian, Azzalin Claus M, Hug Nele, Deplazes Anna, Peter Matthias, Lingner Joachim
Swiss Institute for Experimental Cancer Research (ISREC), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
Nucleic Acids Res. 2007;35(22):7688-97. doi: 10.1093/nar/gkm912. Epub 2007 Nov 4.
The Smg proteins Smg5, Smg6 and Smg7 are involved in nonsense-mediated RNA decay (NMD) in metazoans, but no orthologs have been found in the budding yeast Saccharomyces cerevisiae. Sequence alignments reveal that yeast Ebs1p is similar in structure to the human Smg5-7, with highest homology to Smg7. We demonstrate here that Ebs1p is involved in NMD and behaves similarly to human Smg proteins. Indeed, both loss and overexpression of Ebs1p results in stabilization of NMD targets. However, Ebs1-loss in yeast or Smg7-depletion in human cells only partially disrupts NMD and in the latter, Smg7-depletion is partially compensated for by Smg6. Ebs1p physically interacts with the NMD helicase Upf1p and overexpressed Ebs1p leads to recruitment of Upf1p into cytoplasmic P-bodies. Furthermore, Ebs1p localizes to P-bodies upon glucose starvation along with Upf1p. Overall our findings suggest that NMD is more conserved in evolution than previously thought, and that at least one of the Smg5-7 proteins is conserved in budding yeast.
Smg蛋白Smg5、Smg6和Smg7参与后生动物的无义介导的RNA降解（NMD），但在芽殖酵母酿酒酵母中未发现直系同源物。序列比对显示，酵母Ebs1p在结构上与人类Smg5 - 7相似，与Smg7的同源性最高。我们在此证明Ebs1p参与NMD，并且其行为与人类Smg蛋白相似。实际上，Ebs1p的缺失和过表达都会导致NMD靶标的稳定。然而，酵母中Ebs1的缺失或人类细胞中Smg7的缺失仅部分破坏NMD，并且在后者中，Smg7的缺失部分地由Smg6补偿。Ebs1p与NMD解旋酶Upf1p发生物理相互作用，过表达的Ebs1p导致Upf1p募集到细胞质中的P小体中。此外，在葡萄糖饥饿时，Ebs1p与Upf1p一起定位于P小体。总体而言，我们的研究结果表明，NMD在进化中比以前认为的更保守，并且Smg5 - 7蛋白中的至少一种在芽殖酵母中是保守的。
