Effects of ribosomal proteins S1, S2 and the DeaD/CsdA DEAD-box helicase on translation of leaderless and canonical mRNAs in Escherichia coli
Effects of ribosomal proteins S1, S2 and the DeaD/CsdA DEAD-box helicase on translation of leaderless and canonical mRNAs in Escherichia coli
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DOI：
10.1046/j.1365-2958.2002.02971.x
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发表时间：
2002-06-01
影响因子：
3.6
通讯作者：
Bläsi, U
中科院分区：
文献类型：
--
作者：
Moll, I;Grill, S;Bläsi, U
以 AUG 起始密码子开始的无领导者 mRNA 存在于所有生命王国中。先前已报道，在核糖体蛋白 S2 缺陷的大肠杆菌 rpsB 突变体中，无前导序列 lambdacI mRNA 的翻译受到刺激。在这里，我们利用大肠杆菌 rpsB(ts) 突变体在分子水平上研究了这种现象。对非许可条件下分离的核糖体的分析表明，除了核糖体蛋白 S2 之外，不存在核糖体蛋白 S1，这表明 S2 对于 S1 与 30S 核糖体亚基的结合至关重要。体外翻译测定和无前导序列 mRNA 在不允许的温度下体内的选择性翻译证实并扩展了先前的体外核糖体结合研究，因为 S1 对于无前导序列 mRNA 的翻译确实是可有可无的。 deaD/csdA 基因编码“DeaD/CsdA”DEAD-box 解旋酶，已被分离为 rpsB(ts) 突变的多拷贝抑制基因。在这里，我们表明，在 rpsB(ts) 菌株中，质粒携带的 deaD/csdA 基因的表达在不允许的温度下恢复了核糖体上的 S1 和 S2，这反过来又导致影响典型 mRNA 的翻译缺陷受到抑制。这些数据根据模型进行讨论，其中 DeaD/CsdA 参与核糖体生物合成而不是直接作用于 mRNA。
Leaderless mRNAs beginning with the AUG initiating codon occur in all kingdoms of life. It has been previously reported that translation of the leaderless lambdacI mRNA is stimulated in an Escherichia coli rpsB mutant deficient in ribosomal protein S2. Here, we have studied this phenomenon at the molecular level by making use of an E. coli rpsB(ts) mutant. The analysis of the ribosomes isolated under the non-permissive conditions revealed that in addition to ribosomal protein S2, ribosomal protein S1 was absent, demonstrating that S2 is essential for binding of S1 to the 30S ribosomal subunit. In vitro translation assays and the selective translation of a leaderless mRNA in vivo at the non-permissive temperature corroborate and extend previous in vitro ribosome binding studies in that S1 is indeed dispensable for translation of leaderless mRNAs. The deaD/csdA gene, encoding the 'DeaD/CsdA' DEAD-box helicase, has been isolated as a multicopy suppressor of rpsB(ts) mutations. Here, we show that expression of a plasmid borne deaD/csdA gene restores both S1 and S2 on the ribosome at the non-permissive temperature in the rpsB(ts) strain, which in turn leads to suppression of the translational defect affecting canonical mRNAs. These data are discussed in terms of a model, wherein DeaD/CsdA is involved in ribosome biogenesis rather than acting directly on mRNA.