Department of Genetic Engineering and Graduate School of Biotechnology, College of Life Sciences, Kyung Hee University, Yongin 17104, South Korea.
Division of Microbiology, Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon 16419, South Korea.
Sci Rep. 2017 Feb 9;7:42098. doi: 10.1038/srep42098.
When a ribosome translates mRNA sequences, the ribosome often stalls at certain codons because it is hard to translate. Consecutive proline codons are such examples that induce ribosome stalling and elongation factor P (EF-P) is required for the stalled ribosome to continue translation at those consecutive proline codons. We found that EF-P is required for translation of the mgtB gene encoding a Mg transporter in the mgtCBR virulence operon from the intracellular pathogen Salmonella enterica serovar Typhimurium. Salmonella lacking EF-P decreases MgtB protein levels in a manner dependent on consecutive proline codons located in the mgtB coding region despite increasing transcription of the mgtCBR operon via the mgtP open reading frame in the leader RNA, resulting in an altered ratio between MgtC and MgtB proteins within the operon. Substitution of the consecutive proline codons to alanine codons eliminates EF-P-mediated control of the mgtB gene during infection and thus contributes to Salmonella's survival inside macrophages where Salmonella experiences low levels of EF-P. This suggests that this pathogen utilizes a strategy to coordinate expression of virulence genes by an evolutionarily conserved translation factor.
当核糖体翻译 mRNA 序列时，核糖体经常在某些密码子处停滞不前，因为很难翻译。连续的脯氨酸密码子就是这样的例子，它们会导致核糖体停滞不前，而延伸因子 P（EF-P）是核糖体在这些连续脯氨酸密码子上继续翻译所必需的。我们发现，EF-P 是编码内病原体沙门氏菌肠道亚种毒力操纵子中 Mg 转运蛋白的 mgtB 基因翻译所必需的。EF-P 缺失的沙门氏菌会降低 MgtB 蛋白水平，这种方式依赖于位于 mgtB 编码区的连续脯氨酸密码子，尽管通过位于前导 RNA 中的 mgtP 开放阅读框增加了 mgtCBR 操纵子的转录，但导致操纵子内 MgtC 和 MgtB 蛋白之间的比例发生改变。连续脯氨酸密码子替换为丙氨酸密码子可消除 EF-P 对感染期间 mgtB 基因的调控，从而有助于沙门氏菌在巨噬细胞内的存活，在巨噬细胞中，沙门氏菌经历低水平的 EF-P。这表明这种病原体利用一种策略来通过进化上保守的翻译因子协调毒力基因的表达。
