Neff C L, Sachs A B
Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA.
Mol Cell Biol. 1999 Aug;19(8):5557-64. doi: 10.1128/MCB.19.8.5557.
The initiation of translation in eukaryotes requires several multisubunit complexes, including eukaryotic translation initiation factor 4F (eIF4F). In higher eukaryotes eIF4F is composed of the cap binding protein eIF4E, the adapter protein eIF4G, and the RNA-stimulated ATPase eIF4A. The association of eIF4A with Saccharomyces cerevisiae eIF4F has not yet been demonstrated, and therefore the degree to which eIF4A's conserved function relies upon this association has remained unclear. Here we report an interaction between yeast eIF4G and eIF4A. Specifically, we found that the growth arrest phenotype associated with three temperature-sensitive alleles of yeast eIF4G2 was suppressed by excess eIF4A and that this suppression was allele specific. In addition, in vitro translation extracts derived from an eIF4G2 mutant strain could be heat inactivated, and this inactivation could be reversed upon the addition of recombinant eIF4A. Finally, in vitro binding between yeast eIF4G and eIF4A was demonstrated, as was diminished binding between mutant eIF4G2 proteins and eIF4A. In total, these data indicate that yeast eIF4G and eIF4A physically associate and that this association performs an essential function.
真核生物中的翻译起始需要几种多亚基复合物，包括真核翻译起始因子4F（eIF4F）。在高等真核生物中，eIF4F由帽结合蛋白eIF4E、衔接蛋白eIF4G和RNA刺激的ATP酶eIF4A组成。eIF4A与酿酒酵母eIF4F的关联尚未得到证实，因此eIF4A保守功能依赖于这种关联的程度仍不清楚。在此我们报道酵母eIF4G和eIF4A之间存在相互作用。具体而言，我们发现与酵母eIF4G2的三个温度敏感等位基因相关的生长停滞表型被过量的eIF4A抑制，并且这种抑制具有等位基因特异性。此外，源自eIF4G2突变株的体外翻译提取物可被热灭活，而这种灭活在添加重组eIF4A后可被逆转。最后，证明了酵母eIF4G和eIF4A之间的体外结合，以及突变的eIF4G2蛋白与eIF4A之间结合的减少。总体而言，这些数据表明酵母eIF4G和eIF4A在物理上相互关联，并且这种关联发挥着重要功能。
