Department of Molecular Microbiology, John Innes Centre, Norwich, NR4 7UH, UK.
Nat Commun. 2024 Jun 4;15(1):4749. doi: 10.1038/s41467-024-49114-2.
Gene Transfer Agents (GTAs) are phage-like particles that cannot self-multiply and be infectious. Caulobacter crescentus, a bacterium best known as a model organism to study bacterial cell biology and cell cycle regulation, has recently been demonstrated to produce bona fide GTA particles (CcGTA). Since C. crescentus ultimately die to release GTA particles, the production of GTA particles must be tightly regulated and integrated with the host physiology to prevent a collapse in cell population. Two direct activators of the CcGTA biosynthetic gene cluster, GafY and GafZ, have been identified, however, it is unknown how GafYZ controls transcription or how they coordinate gene expression of the CcGTA gene cluster with other accessory genes elsewhere on the genome for complete CcGTA production. Here, we show that the CcGTA gene cluster is transcriptionally co-activated by GafY, integration host factor (IHF), and by GafZ-mediated transcription anti-termination. We present evidence that GafZ is a transcription anti-terminator that likely forms an anti-termination complex with RNA polymerase, NusA, NusG, and NusE to bypass transcription terminators within the 14 kb CcGTA cluster. Overall, we reveal a two-tier regulation that coordinates the synthesis of GTA particles in C. crescentus.
基因转移因子（GTAs）是一种类似噬菌体的颗粒，不能自我复制和具有感染力。新月柄杆菌，一种以研究细菌细胞生物学和细胞周期调控的模式生物而闻名的细菌，最近被证明能产生真正的 GTA 颗粒（CcGTA）。由于新月柄杆菌最终会死亡以释放 GTA 颗粒，因此 GTA 颗粒的产生必须受到严格的调控，并与宿主生理学相整合，以防止细胞群体崩溃。已经鉴定出两个直接激活 CcGTA 生物合成基因簇的 GafY 和 GafZ，但尚不清楚 GafYZ 如何控制转录，以及它们如何协调 CcGTA 基因簇与基因组其他地方的其他辅助基因的基因表达，以完成 CcGTA 的产生。在这里，我们表明 GafY、整合宿主因子（IHF）和 GafZ 介导的转录抗终止共同激活 CcGTA 基因簇的转录。我们提供的证据表明，GafZ 是一种转录抗终止因子，可能与 RNA 聚合酶、NusA、NusG 和 NusE 形成抗终止复合物，以绕过 14kb 的 CcGTA 簇内的转录终止子。总的来说，我们揭示了一种协调新月柄杆菌中 GTA 颗粒合成的两级调控机制。
