Bandyopadhyay Amitabha, Lakshmanan Viswanathan, Matsumoto Tomohiro, Chang Eric C, Maitra Umadas
Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
J Biol Chem. 2002 Jan 18;277(3):2360-7. doi: 10.1074/jbc.M107790200. Epub 2001 Nov 8.
The protein encoded by the fission yeast gene, moe1(+) is the homologue of the p66/eIF3d subunit of mammalian translation initiation factor eIF3. In this study, we show that in fission yeast, Moe1 physically associates with eIF3 core subunits as well as with 40 S ribosomal particles as a constituent of the eIF3 protein complex that is similar in size to multisubunit mammalian eIF3. However, strains lacking moe1(+) (Deltamoe1) are viable and show no gross defects in translation initiation, although the rate of translation in the Deltamoe1 cells is about 30-40% slower than wild-type cells. Mutant Deltamoe1 cells are hypersensitive to caffeine and defective in spore formation. These phenotypes of Deltamoe1 cells are similar to those reported previously for deletion of the fission yeast int6(+) gene that encodes the fission yeast homologue of the p48/Int6/eIF3e subunit of mammalian eIF3. Further analysis of eIF3 subunits in Deltamoe1 or Deltaint6 cells shows that in these deletion strains, while all the eIF3 subunits are bound to 40 S particles, dissociation of ribosome-bound eIF3 results in the loss of stable association between the eIF3 subunits. In contrast, eIF3 isolated from ribosomes of wild-type cells are associated with one another in a protein complex. These observations suggest that Moe1 and spInt6 are each required for stable association of eIF3 subunits in fission yeast.
裂殖酵母基因moe1(+)编码的蛋白质是哺乳动物翻译起始因子eIF3的p66/eIF3d亚基的同源物。在本研究中，我们发现，在裂殖酵母中，Moe1作为eIF3蛋白复合体的一个组成部分，与eIF3核心亚基以及40S核糖体颗粒发生物理关联，该复合体大小与多亚基哺乳动物eIF3相似。然而，缺乏moe1(+)的菌株（Deltamoe1）能够存活，并且在翻译起始过程中没有明显缺陷，尽管Deltamoe1细胞中的翻译速率比野生型细胞慢约30 - 40%。突变的Deltamoe1细胞对咖啡因高度敏感，并且在孢子形成方面存在缺陷。Deltamoe1细胞的这些表型与之前报道的裂殖酵母int6(+)基因缺失的表型相似，int6(+)基因编码哺乳动物eIF3的p48/Int6/eIF3e亚基的裂殖酵母同源物。对Deltamoe1或Deltaint6细胞中eIF3亚基的进一步分析表明，在这些缺失菌株中，虽然所有eIF3亚基都与40S颗粒结合，但核糖体结合的eIF3解离会导致eIF3亚基之间稳定关联的丧失。相比之下，从野生型细胞核糖体中分离的eIF3在蛋白质复合体中相互关联。这些观察结果表明，Moe1和spInt6对于裂殖酵母中eIF3亚基的稳定关联都是必需的。
