ABSTRACT
Poly-ADP-ribosylation (PARylation) is regarded as a protein-specific modification. However, some PARPs were recently shown to modify DNA termini in vitro. Here, we use ultrasensitive mass spectrometry (LC-MS/MS), anti-PAR antibodies, and anti-PAR reagents to show that mammalian DNA is physiologically PARylated and to different levels in primary tissues. Inhibition of PAR glycohydrolase (PARG) increases DNA PARylation, supporting that the modification is reversible. DNA PARylation requires PARP1 and in vitro PARP1 PARylates single-stranded DNA, while PARG reverts the modification. DNA PARylation occurs at the N1-position of adenosine residues to form N1-Poly(ADP-ribosyl)-deoxyadenosine. Through partial hydrolysis of mammalian gDNA we identify PAR-DNA via the diagnostic deamination product N1-ribosyl-deoxyinosine to occur in vivo. The discovery of N1-adenosine PARylation as a DNA modification establishes the conceptual and methodological framework to elucidate its biological relevance and extends the role of PARP enzymes.
Subject(s)
Poly ADP Ribosylation , Poly(ADP-ribose) Polymerase Inhibitors , Adenosine , Adenosine Diphosphate , Animals , Chromatography, Liquid , DNA/metabolism , DNA, Single-Stranded , Deoxyadenosines , Glycoside Hydrolases/metabolism , Mammals/genetics , Poly (ADP-Ribose) Polymerase-1/metabolism , Poly Adenosine Diphosphate Ribose/metabolism , Tandem Mass SpectrometryABSTRACT
We report the isolation, identification, and assemblies of three antibiotic-producing soil bacteria (Staphylococcus pasteuri, Peribacillus butanolivorans, and Micrococcus yunnanensis) that inhibit the growth of Neisseria commensals in coculture. With pathogenic Neisseria strains becoming increasingly resistant to antibiotics, bioprospecting for novel antimicrobials using commensal relatives may facilitate discovery of clinically useful drugs.
ABSTRACT
The proposal that N6-methyl-deoxyadenosine (m6dA) acts as an epigenetic mark in mammals remains controversial. Using isotopic labeling coupled to ultrasensitive mass spectrometry, we confirm the presence of low-level m6dA in mammalian DNA. However, the bulk of genomic m6dA originates from ribo-N6-methyladenosine, which is processed via the nucleotide-salvage pathway and misincorporated by DNA polymerases. Our results argue against m6dA acting as a heritable, epigenetic DNA mark in mammalian cells.
Subject(s)
DNA/chemistry , DNA/metabolism , Deoxyadenosines/analysis , Genomics , Isotope Labeling/methods , Amino Acids/chemistry , Animals , Cell Line , DNA Methylation , DNA-Directed DNA Polymerase/metabolism , Genome , Humans , Mass Spectrometry , Methyltransferases/metabolism , MiceABSTRACT
Base excision repair (BER) functions not only in the maintenance of genomic integrity but also in active DNA demethylation and epigenetic gene regulation. This dual role raises the question if phenotypic abnormalities resulting from deficiency of BER factors are due to DNA damage or impaired DNA demethylation. Here we investigate the bifunctional DNA glycosylases/lyases NEIL1 and NEIL2, which act in repair of oxidative lesions and in epigenetic demethylation. Neil-deficiency in Xenopus embryos and differentiating mouse embryonic stem cells (mESCs) leads to a surprisingly restricted defect in cranial neural crest cell (cNCC) development. Neil-deficiency elicits an oxidative stress-induced TP53-dependent DNA damage response, which impairs early cNCC specification. Epistasis experiments with Tdg-deficient mESCs show no involvement of epigenetic DNA demethylation. Instead, Neil-deficiency results in oxidative damage specific to mitochondrial DNA, which triggers a TP53-mediated intrinsic apoptosis. Thus, NEIL1 and NEIL2 DNA glycosylases protect mitochondrial DNA against oxidative damage during neural crest differentiation.
