Dalia Triana N, Dalia Ankur B
Department of Biology, Indiana University, Bloomington, Indiana, USA.
J Bacteriol. 2025 Jan 31;207(1):e0041924. doi: 10.1128/jb.00419-24. Epub 2024 Dec 13.
Natural transformation (NT) is a conserved mechanism of horizontal gene transfer in bacterial species. During this process, DNA is taken up into the cytoplasm where it can be integrated into the host genome by homologous recombination. We have previously shown that some cytoplasmic exonucleases inhibit NT by degrading ingested DNA prior to its successful recombination. However, one exonuclease, SbcB, counterintuitively promotes NT in . Here, through a systematic analysis of the distinct steps of NT, we show that SbcB acts downstream of DNA uptake into the cytoplasm, but upstream of recombinational branch migration. Through mutational analysis, we show that SbcB promotes NT in a manner that does not rely on its exonuclease activity. Finally, we provide genetic evidence that SbcB directly interacts with the primary bacterial recombinase, RecA. Together, these data advance our molecular understanding of horizontal gene transfer in and reveal that SbcB promotes homologous recombination during NT in a manner that does not rely on its canonical exonuclease activity.
Horizontal gene transfer by natural transformation contributes to the spread of antibiotic resistance and virulence factors in bacterial species. Here, we study how one protein, SbcB, helps facilitate this process in the facultative bacterial pathogen . SbcB is a well-known for its exonuclease activity (i.e., the ability to degrade the ends of linear DNA). Through this study, we uncover that while SbcB is important for natural transformation, it does not facilitate this process using its exonuclease activity. Thus, this work helps further our understanding of the molecular events required for this conserved evolutionary process and uncovers a function for SbcB beyond its canonical exonuclease activity.
自然转化（NT）是细菌物种中水平基因转移的一种保守机制。在此过程中，DNA被摄取到细胞质中，在那里它可以通过同源重组整合到宿主基因组中。我们之前已经表明，一些细胞质核酸外切酶通过在摄入的DNA成功重组之前将其降解来抑制自然转化。然而，有一种核酸外切酶SbcB却出人意料地在[具体细菌名称未给出]中促进自然转化。在这里，通过对自然转化不同步骤的系统分析，我们表明SbcB在DNA摄取到细胞质之后、重组分支迁移之前发挥作用。通过突变分析，我们表明SbcB以一种不依赖其核酸外切酶活性的方式促进自然转化。最后，我们提供了遗传学证据，证明SbcB直接与主要的细菌重组酶RecA相互作用。总之，这些数据推进了我们对[具体细菌名称未给出]中水平基因转移的分子理解，并揭示SbcB在自然转化过程中促进同源重组的方式不依赖其典型的核酸外切酶活性。
自然转化介导的水平基因转移有助于细菌物种中抗生素抗性和毒力因子的传播。在这里，我们研究一种蛋白质SbcB如何在兼性细菌病原体[具体细菌名称未给出]中促进这一过程。SbcB以其核酸外切酶活性（即降解线性DNA末端的能力）而闻名。通过这项研究，我们发现虽然SbcB对自然转化很重要，但它并不是利用其核酸外切酶活性来促进这一过程的。因此，这项工作有助于进一步加深我们对这一保守进化过程所需分子事件的理解，并揭示了SbcB除其典型核酸外切酶活性之外的一种功能。
