RdgB acts to avoid chromosome fragmentation in Escherichia coli
RdgB acts to avoid chromosome fragmentation in Escherichia coli
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DOI：
10.1046/j.1365-2958.2003.03540.x
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发表时间：
2003-06-01
影响因子：
3.6
通讯作者：
Kuzminov, A
中科院分区：
文献类型：
--
作者：
Bradshaw, JS;Kuzminov, A
细菌RecA蛋白是修复使整个染色体失效的双链DNA损伤所必需的。recA突变体是可行的，这表明相当大的细胞能力，以避免这些染色体致残病变。recA依赖性突变体揭示了染色体损伤避免途径。在这里，我们描述了这样一个突变体，rdgB/yggV，缺乏一个假定的肌苷/黄苷三磷酸酶，保守的整个王国的生活。通过对DNA-次黄嘌呤/黄嘌呤特异性的核酸内切酶V（gpnfi）的失活抑制rdgB recA致死性，表明RdgB要么拦截不适当的DNA前体dITP/dXTP，要么在掺入的次黄嘌呤/黄嘌呤的切除修复中在EndoV的下游起作用。我们发现，从rdgB突变体中分离的DNA含有EndoV可识别的修饰，而从nfi突变体中分离的DNA则没有，这证实了rdgB对dITP/dXTP的拦截。rdgB recBC细胞是不能存活的，而rdgB recF细胞是健康的，这表明rdgB突变体中的染色体遭受双链断裂。在rdgB recBC突变体中确实观察到染色体片段化，并且在rdgB recBC nfi突变体中受到抑制。因此，避免染色体损伤的一种方法是通过拦截dITP/dXTP来防止次黄嘌呤/黄嘌呤掺入DNA。
Bacterial RecA protein is required for repair of two-strand DNA lesions that disable whole chromosomes. recA mutants are viable, suggesting a considerable cellular capacity to avoid these chromosome-disabling lesions. recA -dependent mutants reveal chromosomal lesion avoidance pathways. Here we characterize one such mutant, rdgB/yggV, deficient in a putative inosine/xanthosine triphosphatase, conserved throughout kingdoms of life. The rdgB recA lethality is suppressed by inactivation of endonuclease V (gpnfi) specific for DNA-hypoxanthines/xanthines, suggesting that RdgB either intercepts improper DNA precursors dITP/dXTP or works downstream of EndoV in excision repair of incorporated hypoxathines/xanthines. We find that DNA isolated from rdgB mutants contains EndoV-recognizable modifications, whereas DNA from nfi mutants does not, substantiating the dITP/dXTP interception by RdgB. rdgB recBC cells are inviable, whereas rdgB recF cells are healthy, suggesting that chromosomes in rdgB mutants suffer double-strand breaks. Chromosomal fragmentation is indeed observed in rdgB recBC mutants and is suppressed in rdgB recBC nfi mutants. Thus, one way to avoid chromosomal lesions is to prevent hypoxanthine/xanthine incorporation into DNA via interception of dITP/dXTP.