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Related Concept Videos

Inhibitors of Bacterial DNA Synthesis01:28

Inhibitors of Bacterial DNA Synthesis

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Bacterial pathogens depend on precise and efficient DNA replication to sustain infection. Two type II topoisomerases—DNA gyrase and topoisomerase IV—are critical to this process, as they resolve DNA supercoiling and unlink chromosomes during replication. Fluoroquinolones, synthetic derivatives of quinolones, exploit this mechanism by stabilizing the transient DNA–enzyme cleavage complex, preventing strand religation, and causing lethal double-strand breaks. These...
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For successful DNA replication, the unwinding of double-stranded DNA must be accompanied by stabilization and protection of the separated single strands of the DNA. This crucial task is performed by single-strand DNA-binding (SSB) proteins. They bind to the DNA in a sequence-independent manner, which means that the nitrogenous bases of the DNA need not be present in a specific order for binding of SSB proteins to it. The binding of SSB proteins straightens single-stranded DNA (ssDNA) and makes...
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Topoisomerases are enzymes that relax overwound DNA molecules during various cell processes, including DNA replication and transcription. These enzymes regulate positive and negative DNA supercoiling without changing the nucleotide sequence. DNA overwinding in a clockwise direction results in positively supercoiled DNA, whereas underwinding in a counterclockwise direction produces negatively supercoiled DNA.
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The basic reaction of homologous recombination (HR) involves two chromatids that contain DNA sequences sharing a significant stretch of identity. One of these sequences uses a strand from another as a template to synthesize DNA in an enzyme-catalyzed reaction. The final product is a novel amalgamation of the two substrates. To ensure an accurate recombination of sequences, HR is restricted to the S and G2 phases of the cell cycle. At these stages, the DNA has been replicated already and the...
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Bacteriophages, or phages, are viruses that specifically infect bacteria, utilizing their genetic material to hijack host cellular machinery for replication. DNA bacteriophages employ single-stranded DNA (ssDNA) or double-stranded DNA (dsDNA) genomes. These phages exhibit diverse replication strategies and host interactions, influencing their ecological roles and applications in biotechnology and medicine.ssDNA BacteriophagesssDNA phages, with their small genomes, utilize unique strategies to...
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DNA probes are fragments of DNA labeled with a reporter tag to enable their detection or purification. The resulting labeled DNA probes can then hybridize to target nucleic acid sequences through complementary base-pairing, and may be used to recover or identify these regions.
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Related Experiment Video

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A Simple, Rapid, and Quantitative Assay to Measure Repair of DNA-protein Crosslinks on Plasmids Transfected into Mammalian Cells
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The colibactin warhead crosslinks DNA.

Maria I Vizcaino1, Jason M Crawford2

  • 11] Department of Chemistry, Yale University, New Haven, Connecticut 06510, USA [2] Chemical Biology Institute, Yale University, West Haven, Connecticut 06516, USA.

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|April 23, 2015
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Researchers identified the unstable, DNA-damaging colibactin warhead from Escherichia coli. This finding advances understanding of how gut bacteria contribute to colorectal cancer initiation via small molecules.

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Area of Science:

  • Microbiology and Molecular Biology
  • Cancer Research
  • Metabolomics

Background:

  • Human microbiota metabolites are crucial for host-microbe interactions but remain largely uncharacterized.
  • Certain Escherichia coli strains are linked to inflammation-induced colorectal cancer via unknown small molecules.
  • Colibactin, produced by a non-ribosomal peptide-polyketide hybrid pathway, is implicated but its genotoxic small molecules are unstable and elusive.

Purpose of the Study:

  • To characterize the unstable, genotoxic small molecule responsible for DNA damage and cancer initiation by specific Escherichia coli strains.
  • To elucidate the structure of the colibactin warhead, a key component in the cancer-promoting pathway.

Main Methods:

  • Utilized metabolomic analyses to guide the research.
  • Employed Nuclear Magnetic Resonance (NMR) spectroscopy for structural determination.
  • Conducted bioinformatics-guided isotopic labeling studies.

Main Results:

  • Characterized the colibactin warhead as an unprecedented substituted spirobicyclic structure.
  • Demonstrated that the colibactin warhead crosslinks duplex DNA in vitro.
  • Provided direct experimental evidence for colibactin's DNA-damaging activity.

Conclusions:

  • The identified colibactin warhead structure provides a molecular basis for its genotoxicity.
  • The findings support novel models for both colibactin biosynthesis and its mechanism of action in promoting cancer.
  • This research deepens the understanding of microbial metabolites in human health and disease, specifically colorectal cancer.