Microbiology Institute Mi Kaixia team reveals the molecular mechanism of mycobacterial epigenetic regulation of isoniazid resistance

Tuberculosis is a worldwide infectious disease caused by the airborne transmission of Mycobacterium tuberculosis
.

According to the Global Tuberculosis Report released by the World Health Organization in 2021, there will be approximately 9.
9 million new cases worldwide in 2020, and approximately 1.
5 million people will die of tuberculosis
.


Affected by the COVID-19 pandemic, the cause of death from tuberculosis as a single source of infection in 2020 will drop to the second place
.

Drug-resistant tuberculosis remains a public health threat
.

Understanding how Mycobacterium tuberculosis mutates and evolves in the host to produce drug resistance will provide theoretical guidance for improving tuberculosis treatment and control strategies
.


Mycobacterium tuberculosis is genetically static, has a low mutation rate, and has evolved through single nucleotide polymorphisms
.

However, in the case of continuous chemotherapy, a small number of tuberculosis bacteria will eventually develop widespread antibiotic resistance
.

It is not yet clear why this genetically stable organism can adapt so quickly to antibiotic treatment and the immune pressure of the infected host
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Microbial epigenetics is an important emerging field for studying the formation of microbial diversity, gene regulation, evolutionary inheritance and phenotypic analysis
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The most common DNA methylation in bacteria is on adenine (N6-methyladenine, 6mA).
There are 3 types of methyltransferases in tuberculosis-MamA, MamB and HsdM
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The 6mA methylome analysis of clinically isolated Mycobacterium tuberculosis shows that DNA modification helps the bacteria quickly adapt to changing environmental pressures; different evolutionary lineages of tuberculosis come from different geographic regions, and the genetic variation of these tuberculosis subgroups affects resistance The evolution of medicinal properties
.

There are few basic researches on DNA methylation of tuberculosis.
Michelle’s team constructed different HsdM recombinant strains through genetic methods, and screened antibiotics for clinical treatment of tuberculosis including isoniazid (INH), rifampicin (RFP), Streptomycin (STR), ethambutol (EMB), ciprofloxacin (CIP) and ofloxacin (OFX) (Figure 1), compared with wild type, hsdM knockout bacteria are highly resistant to INH
.

Using Pacbio's third-generation single-molecule real-time sequencing technology (Single-Molecule Real-Time, SMRT), 219 HsdM methylated substrates were identified
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Bioinformatics analysis showed that most HsdM-modified genes are enriched in respiratory and energy-related pathways
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The results of qPCR analysis showed that the modification of HsdM affected gene transcription
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In the latent infection model, ΔhsdM has the advantage of hypoxic survival compared with wild-type BCG, and HsdM regulates the expression level of the latent resurrection-related gene trcR
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Based on the research results, we propose a new molecular mechanism for mycobacterial epigenetic regulation of isoniazid resistance--HsdM modifies the transcription level of genes through methylation modification, which changes the redox state of mycobacteria, thereby reducing tuberculosis bacteria Sensitivity to isoniazid (Figure 2)
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Research shows that epigenetics plays an important role in mycobacterial resistance, and research provides new ideas for antibiotic target selection and antibiotic development
.

Figure 1.
HsdM reduces the drug sensitivity of BCG to isoniazid Figure 2.
HsdM modulates the isoniazid resistance of tuberculosis bacteria
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The research team Assistant Researcher Hu Xinling and Assistant Researcher Zhou Xintong are the co-authors of the article.
Researcher Mi Kaixia is the corresponding author.
Researcher Zhu Baoli from the Institute of Microbiology, Chinese Academy of Sciences and Professor Hu Yongfei from China Agricultural University are co-authors
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This work was supported by the National Key Research and Development Program, the National Natural Science Foundation of China, the International Joint Research Project of the Institute of Medical Research of the University of Tokyo, and the Open Project of the Key Laboratory of Pediatric Critical Disease Research of the Ministry of Education
.