Altmann M, Müller P P, Wittmer B, Ruchti F, Lanker S, Trachsel H
Institute of Biochemistry and Molecular Biology, University of Berne, Switzerland.
EMBO J. 1993 Oct;12(10):3997-4003. doi: 10.1002/j.1460-2075.1993.tb06077.x.
The TIF3 gene of Saccharomyces cerevisiae was cloned and sequenced. The deduced amino acid sequence shows 26% identity with the sequence of mammalian translation initiation factor eIF-4B. The TIF3 gene is not essential for growth; however, its disruption results in a slow growth and cold-sensitive phenotype. In vitro translation of total yeast RNA in an extract from a TIF3 gene-disrupted strain is reduced compared with a wild-type extract. The translational defect is more pronounced at lower temperatures and can be corrected by the addition of wild-type extract or mammalian eIF-4B, but not by addition of mutant extract. In vivo translation of beta-galactosidase reporter mRNA with varying degree of RNA secondary structure in the 5' leader region in a TIF3 gene-disrupted strain shows preferential inhibition of translation of mRNA with more stable secondary structure. This indicates that Tif3 protein is an RNA helicase or contributes to RNA helicase activity in vivo.
酿酒酵母的TIF3基因被克隆并测序。推导的氨基酸序列与哺乳动物翻译起始因子eIF-4B的序列显示出26%的同一性。TIF3基因对于生长不是必需的；然而，其缺失会导致生长缓慢和冷敏感表型。与野生型提取物相比，在TIF3基因缺失菌株的提取物中对总酵母RNA进行的体外翻译减少。翻译缺陷在较低温度下更明显，并且可以通过添加野生型提取物或哺乳动物eIF-4B来纠正，但不能通过添加突变提取物来纠正。在TIF3基因缺失菌株中对5'前导区具有不同程度RNA二级结构的β-半乳糖苷酶报告mRNA进行体内翻译，结果显示对具有更稳定二级结构的mRNA的翻译有优先抑制作用。这表明Tif3蛋白是一种RNA解旋酶或在体内有助于RNA解旋酶活性。
