Elfenbein Johanna R, Knodler Leigh A, Nakayasu Ernesto S, Ansong Charles, Brewer Heather M, Bogomolnaya Lydia, Adams L Garry, McClelland Michael, Adkins Joshua N, Andrews-Polymenis Helene L
Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas, United States of America; Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, United States of America.
Paul G. Allen School of Global Animal Health, College of Veterinary Medicine, Washington State University, Pullman, Washington, United States of America.
PLoS Genet. 2015 Sep 14;11(9):e1005472. doi: 10.1371/journal.pgen.1005472. eCollection 2015 Sep.
Multicopy single-stranded DNAs (msDNAs) are hybrid RNA-DNA molecules encoded on retroelements called retrons and produced by the action of retron reverse transcriptases. Retrons are widespread in bacteria but the natural function of msDNA has remained elusive despite 30 years of study. The major roadblock to elucidation of the function of these unique molecules has been the lack of any identifiable phenotypes for mutants unable to make msDNA. We report that msDNA of the zoonotic pathogen Salmonella Typhimurium is necessary for colonization of the intestine. Similarly, we observed a defect in intestinal persistence in an enteropathogenic E. coli mutant lacking its retron reverse transcriptase. Under anaerobic conditions in the absence of msDNA, proteins of central anaerobic metabolism needed for Salmonella colonization of the intestine are dysregulated. We show that the msDNA-deficient mutant can utilize nitrate, but not other alternate electron acceptors in anaerobic conditions. Consistent with the availability of nitrate in the inflamed gut, a neutrophilic inflammatory response partially rescued the ability of a mutant lacking msDNA to colonize the intestine. These findings together indicate that the mechanistic basis of msDNA function during Salmonella colonization of the intestine is proper production of proteins needed for anaerobic metabolism. We further conclude that a natural function of msDNA is to regulate protein abundance, the first attributable function for any msDNA. Our data provide novel insight into the function of this mysterious molecule that likely represents a new class of regulatory molecules.
多拷贝单链DNA（msDNA）是一种RNA - DNA杂交分子，由称为反转录子的逆转录元件编码，并通过反转录子逆转录酶的作用产生。反转录子在细菌中广泛存在，但尽管经过30年的研究，msDNA的天然功能仍然难以捉摸。阐明这些独特分子功能的主要障碍是无法产生msDNA的突变体缺乏任何可识别的表型。我们报告说，人畜共患病原体鼠伤寒沙门氏菌的msDNA对于肠道定殖是必需的。同样，我们在缺乏反转录子逆转录酶的肠致病性大肠杆菌突变体中观察到肠道持久性缺陷。在没有msDNA的厌氧条件下，沙门氏菌在肠道定殖所需的中心厌氧代谢蛋白的表达失调。我们表明，缺乏msDNA的突变体可以利用硝酸盐，但在厌氧条件下不能利用其他替代电子受体。与炎症肠道中硝酸盐的可用性一致，嗜中性粒细胞炎症反应部分挽救了缺乏msDNA的突变体在肠道定殖的能力。这些发现共同表明，沙门氏菌在肠道定殖过程中msDNA功能的机制基础是厌氧代谢所需蛋白质的正常产生。我们进一步得出结论，msDNA的天然功能是调节蛋白质丰度，这是任何msDNA的首个可归因功能。我们的数据为这种可能代表一类新的调节分子的神秘分子的功能提供了新的见解。
