SAMRC/NHLS/UCT Molecular Mycobacteriology Research Unit, DSI/NRF Centre of Excellence for Biomedical TB Research, Department of Pathology, University of Cape Town, Cape Town, South Africa.
Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa.
Elife. 2023 Aug 2;12:e75628. doi: 10.7554/eLife.75628.
A DNA damage-inducible mutagenic gene cassette has been implicated in the emergence of drug resistance in during anti-tuberculosis (TB) chemotherapy. However, the molecular composition and operation of the encoded 'mycobacterial mutasome' - minimally comprising DnaE2 polymerase and ImuA' and ImuB accessory proteins - remain elusive. Following exposure of mycobacteria to DNA damaging agents, we observe that DnaE2 and ImuB co-localize with the DNA polymerase III β subunit (β clamp) in distinct intracellular foci. Notably, genetic inactivation of the mutasome in an mutant containing a disrupted β clamp-binding motif abolishes ImuB-β clamp focus formation, a phenotype recapitulated pharmacologically by treating bacilli with griselimycin and in biochemical assays in which this β clamp-binding antibiotic collapses pre-formed ImuB-β clamp complexes. These observations establish the essentiality of the ImuB-β clamp interaction for mutagenic DNA repair in mycobacteria, identifying the mutasome as target for adjunctive therapeutics designed to protect anti-TB drugs against emerging resistance.
一个 DNA 损伤诱导的突变基因盒已被牵连在抗结核（TB）化疗期间药物耐药性的出现。然而，编码的“分枝杆菌突变体”的分子组成和操作——至少包括 DnaE2 聚合酶和 ImuA' 和 ImuB 辅助蛋白——仍然难以捉摸。在分枝杆菌暴露于 DNA 损伤剂后，我们观察到 DnaE2 和 ImuB 与 DNA 聚合酶 III β 亚基（β 夹）在不同的细胞内焦点中共同定位。值得注意的是，在含有破坏的β夹结合基序的突变体中突变体的遗传失活消除了 ImuB-β 夹焦点的形成，这一表型通过用格里西霉素处理杆菌并在生化测定中用这种β夹结合抗生素破坏预先形成的 ImuB-β 夹复合物来重现。这些观察结果确立了 ImuB-β 夹相互作用对于分枝杆菌中诱变 DNA 修复的必要性，将突变体鉴定为设计用于保护抗结核药物免受新出现的耐药性的辅助治疗的靶标。
