Division of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
Mol Microbiol. 2021 Jun;115(6):1138-1151. doi: 10.1111/mmi.14656. Epub 2020 Dec 18.
The H-NS-like proteins MvaT and MvaU act coordinately as global repressors in Pseudomonas aeruginosa by binding to AT-rich regions of the chromosome. Although cells can tolerate loss of either protein, identifying their combined regulatory effects has been challenging because the loss of both proteins is lethal due to induction of prophage Pf4 and subsequent superinfection of the cell. In other bacteria, H-NS promotes the cellular fitness by inhibiting intragenic transcription from AT-rich target regions, preventing them from sequestering RNA polymerase; however, it is not known whether MvaT and MvaU function similarly. Here, we utilize a parental strain that cannot be infected by Pf4 phage to define the collective MvaT and MvaU regulon and demonstrate that the combined loss of both MvaT and MvaU leads to increased intragenic transcription from loci directly controlled by these proteins. We further show that the loss of MvaT and MvaU leads to a striking redistribution of RNA polymerase containing σ to genomic regions vacated by these proteins. Our findings suggest that the ability of H-NS-like proteins to repress intragenic transcription is a universal function of these proteins and point to a second mechanism by which MvaT and MvaU may contribute to the growth of P. aeruginosa.
H-NS 样蛋白 MvaT 和 MvaU 通过与假单胞菌染色体上富含 AT 的区域结合，协调作为全局抑制剂。尽管细胞可以容忍任一蛋白的缺失，但由于 Pf4 噬菌体的诱导和随后细胞的超感染，同时缺失这两种蛋白是致命的，因此确定它们的联合调控作用具有挑战性。在其他细菌中，H-NS 通过抑制富含 AT 的靶区域的基因内转录来促进细胞适应性，防止它们结合 RNA 聚合酶；然而，目前尚不清楚 MvaT 和 MvaU 是否具有类似的功能。在这里，我们利用一种不能被 Pf4 噬菌体感染的亲本菌株来定义 MvaT 和 MvaU 的共同调控组，并证明这两种蛋白的同时缺失会导致这些蛋白直接调控的基因内转录增加。我们进一步表明，MvaT 和 MvaU 的缺失会导致 RNA 聚合酶与这些蛋白占据的基因组区域显著重新分布。我们的研究结果表明，H-NS 样蛋白抑制基因内转录的能力是这些蛋白的普遍功能，并指出了 MvaT 和 MvaU 可能有助于铜绿假单胞菌生长的第二种机制。
