title: Mycobacterial MazG safeguards genetic stability via housecleaning of 5-OH-dCTP.
abstract: Generation of reactive oxygen species and reactive nitrogen species in phagocytes is an important innate immune response mechanism to eliminate microbial pathogens. It is known that deoxynucleotides (dNTPs), the precursor nucleotides to DNA synthesis, are one group of the significant targets for these oxidants and incorporation of oxidized dNTPs into genomic DNA may cause mutations and even cell death. Here we show that the mycobacterial dNTP pyrophosphohydrolase MazG safeguards the bacilli genome by degrading 5-OH-dCTP, thereby, preventing it from incorporation into DNA. Deletion of the (d)NTP pyrophosphohydrolase-encoding mazG in mycobacteria leads to a mutator phenotype both under oxidative stress and in the stationary phase of growth, resulting in increased CG to TA mutations. Biochemical analyses demonstrate that mycobacterial MazG can efficiently hydrolyze 5-OH-dCTP, an oxidized nucleotide that induces CG to TA mutation upon incorporation by polymerase. Moreover, chemical genetic analyses show that direct incorporation of 5-OH-dCTP into mazG-null mutant strain of Mycobacterium smegmatis (Msm) leads to a dose-dependent mutagenesis phenotype, indicating that 5-OH-dCTP is a natural substrate of mycobacterial MazG. Furthermore, deletion of mazG in Mycobacterium tuberculosis (Mtb) leads to reduced survival in activated macrophages and in the spleen of infected mice. This study not only characterizes the mycobacterial MazG as a novel pyrimidine-specific housecleaning enzyme that prevents CG to TA mutation by degrading 5-OH-dCTP but also reveals a genome-safeguarding mechanism for survival of Mtb in vivo.
authors: CAS-Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China ; Department of Microbiology and Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR, China.
authors: Liang-Dong
authors: LD
authors: Lyu
authors: Bi-Kui
authors: BK
authors: Tang
authors: Xiao-Yong
authors: XY
authors: Fan
authors: Hui
authors: H
authors: Ma
authors: Guo-Ping
authors: GP
authors: Zhao
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003845:Deoxycytosine Nucleotides / Q000378:metabolism*; D005260:Female; D016680:Genome, Bacterial; D042822:Genomic Instability / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D050296:Microbial Viability / Q000235:genetics; D020125:Mutation, Missense / Q000235:genetics; D020102:Mycobacterium smegmatis / Q000235:genetics*; D009169:Mycobacterium tuberculosis / Q000235:genetics*; D030781:Organisms, Genetically Modified; D011755:Pyrophosphatases / Q000502:physiology*
chemical_list: C089929:2'-deoxy-5-hydroxycytosine triphosphate; D003845:Deoxycytosine Nucleotides; D011755:Pyrophosphatases