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Inactivation of the DNA repair genes mutS, mutL or the anti-recombination gene mutS2 leads to activation of vitamin B1 biosynthesis genes.

ABSTRACT: Oxidative stress generates harmful reactive oxygen species (ROS) that attack biomolecules including DNA. In living cells, there are several mechanisms for detoxifying ROS and repairing oxidatively-damaged DNA. In this study, transcriptomic analyses clarified that disruption of DNA repair genes mutS and mutL, or the anti-recombination gene mutS2, in Thermus thermophilus HB8, induces the biosynthesis pathway for vitamin B(1), which can serve as an ROS scavenger. In addition, disruption of mutS, mutL, or mutS2 resulted in an increased rate of oxidative stress-induced mutagenesis. Co-immunoprecipitation and pull-down experiments revealed previously-unknown interactions of MutS2 with MutS and MutL, indicating that these proteins cooperatively participate in the repair of oxidatively damaged DNA. These results suggested that bacterial cells sense the accumulation of oxidative DNA damage or absence of DNA repair activity, and signal the information to the transcriptional regulation machinery for an ROS-detoxifying system.

SUBMITTER: Fukui K

PROVIDER: S-EPMC3084264 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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Inactivation of the DNA repair genes mutS, mutL or the anti-recombination gene mutS2 leads to activation of vitamin B1 biosynthesis genes.

Fukui Kenji K Wakamatsu Taisuke T Agari Yoshihiro Y Masui Ryoji R Kuramitsu Seiki S

PloS one 20110428 4

Oxidative stress generates harmful reactive oxygen species (ROS) that attack biomolecules including DNA. In living cells, there are several mechanisms for detoxifying ROS and repairing oxidatively-damaged DNA. In this study, transcriptomic analyses clarified that disruption of DNA repair genes mutS and mutL, or the anti-recombination gene mutS2, in Thermus thermophilus HB8, induces the biosynthesis pathway for vitamin B(1), which can serve as an ROS scavenger. In addition, disruption of mutS, mu ...[more]

PMID: 21552516

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Project description:We analyzed the expression profile of mutS, mutL, or mutS2 deletion mutant strain of Thermus thermophils HB8 during the exponential growth phase. When compared with wild type using t-test (P < 0.01), 8, 111, and 18 genes were over 2-fold up-regulated in mutS, mutL, and mutS2-lacking strains, respectively. Keywords: cell type comparison Wild-type and the mutant strains were precultured in 3 mL of rich medium for two times at 70°C and then subcultured to 1000 mL of rich medium. These cells were cultured at70°C for 300 min , and then cells were harvested from 50 ml of the culture. Total RNA were extracted from wild-type and mutant strains and used for the cDNA synthesis by SuperScript II (Invitrogen, Carlsbad, CA). The cDNA fragments were labeled with GeneChip DNA Labeling Reagent (Affymetrix, Santa Clara, CA), using terminal transferase according to the manufacturer’s instructions. The 3’-terminal-labeled cDNA was hybridized with a TTHB8401a520105F GeneChip (Affymetrix) which contained probe sets of 25-mer oligonucleotides for 2238 ORFs and 1096 intergenic regions. After washing and staining with streptavidin-phycoerythrin (Invitrogen) by GeneChip Fluidics Station 450XP (Affymetrix), the array was scanned by a GeneChip Scanner 3000 (Affymetrix). The image data was scaled to the target intensity by one-step Tukey’s biweight algorithm using GeneChip Operating software, version 1.2 (Affymetrix). The data analysis was performed on the Subio platform version 1.6 (Subio Inc., Tokyo, Japan). The genes which had detection call of “presence” more than 4 times from 8 samples were used for following analysis. The normalized intensities for the mutant strains were calculated by using the intensities for wild-type strains of each data set, and then, the average of these intensities were used. The genes which produced P value < 0.01 in the Student’s t-test were extracted. Among them, the genes whose expression level was different more than 2 fold between two strains were considered as significant. For the biological replication, above experiments were performed three times independently.

Project description:Bacterial MutS proteins are subdivided into two families, MutS1 and MutS2. MutS1 family members recognize DNA replication errors during their participation in the well-characterized mismatch repair (MMR) pathway. In contrast to the well-described function of MutS1, the function of MutS2 in bacteria has remained less clear. In Helicobacter pylori and Thermus thermophilus, MutS2 has been shown to suppress homologous recombination. The role of MutS2 is unknown in the Gram-positive bacterium Bacillus subtilis In this work, we investigated the contribution of MutS2 to maintaining genome integrity in B. subtilis We found that deletion of mutS2 renders B. subtilis sensitive to the natural antibiotic mitomycin C (MMC), which requires homologous recombination for repair. We demonstrate that the C-terminal small MutS-related (Smr) domain is necessary but not sufficient for tolerance to MMC. Further, we developed a CRISPR/Cas9 genome editing system to test if the inducible prophage PBSX was the underlying cause of the observed MMC sensitivity. Genetic analysis revealed that MMC sensitivity was dependent on recombination and not on nucleotide excision repair or a symptom of prophage PBSX replication and cell lysis. We found that deletion of mutS2 resulted in decreased transformation efficiency using both plasmid and chromosomal DNA. Further, deletion of mutS2 in a strain lacking the Holliday junction endonuclease gene recU resulted in increased MMC sensitivity and decreased transformation efficiency, suggesting that MutS2 could function redundantly with RecU. Together, our results support a model where B. subtilis MutS2 helps to promote homologous recombination, demonstrating a new function for bacterial MutS2.ImportanceCells contain pathways that promote or inhibit recombination. MutS2 homologs are Smr-endonuclease domain-containing proteins that have been shown to function in antirecombination in some bacteria. We present evidence that B. subtilis MutS2 promotes recombination, providing a new function for MutS2. We found that cells lacking mutS2 are sensitive to DNA damage that requires homologous recombination for repair and have reduced transformation efficiency. Further analysis indicates that the C-terminal Smr domain requires the N-terminal portion of MutS2 for function in vivo Moreover, we show that a mutS2 deletion is additive with a recU deletion, suggesting that these proteins have a redundant function in homologous recombination. Together, our study shows that MutS2 proteins have adapted different functions that impact recombination.

Project description:BACKGROUND:Acinetobacter baylyi ADP1 is an ideal bacterial strain for high-throughput genetic analysis as the bacterium is naturally transformable. Thus, ADP1 can be used to investigate DNA mismatch repair, a mechanism for repairing mismatched bases. We used the mutS deletion mutant (XH439) and mutL deletion mutant (XH440), and constructed a mutS mutL double deletion mutant (XH441) to investigate the role of the mismatch repair system in A. baylyi. RESULTS:We determined the survival rates after UV irradiation and measured the mutation frequencies, rates and spectra of wild-type ADP1 and mutSL mutant via rifampin resistance assay (RifR assay) and experimental evolution. In addition, transformation efficiencies of genomic DNA in ADP1 and its three mutants were determined. Lastly, the relative growth rates of the wild type strain, three constructed deletion mutants, as well as the rifampin resistant mutants obtained from RifR assays, were measured. All three mutants had higher survival rates after UV irradiation than wild type, especially the double deletion mutant. Three mutants showed higher mutation frequencies than ADP1 and favored transition mutations in RifR assay. All three mutants showed increased mutation rates in the experimental evolution. However, only XH439 and XH441 had higher mutation rates than the wild type strain in RifR assay. XH441 showed higher transformation efficiency than XH438 when donor DNA harbored transition mutations. All three mutants showed higher growth rates than wild-type, and these four strains displayed higher growth rates than almost all their rpoB mutants. The growth rate results showed different amino acid mutations in rpoB resulted in different extents of reduction in the fitness of rifampin resistant mutants. However, the fitness cost brought by the same mutation did not vary with strain background. CONCLUSIONS:We demonstrated that inactivation of both mutS and mutL increased the mutation rates and frequencies in A. baylyi, which would contribute to the evolution and acquirement of rifampicin resistance. The mutS deletion is also implicated in increased mutation rates and frequencies, suggesting that MutL may be activated even in the absence of mutS. The correlation between fitness cost and rifampin resistance mutations in A. baylyi is firstly established.

Dataset Information

Inactivation of the DNA repair genes mutS, mutL or the anti-recombination gene mutS2 leads to activation of vitamin B1 biosynthesis genes.

Publications

Inactivation of the DNA repair genes mutS, mutL or the anti-recombination gene mutS2 leads to activation of vitamin B1 biosynthesis genes.

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