DNA glycosylases for 8-oxoguanine repair in Staphylococcus aureus

• Published in: DNA repair Vol. 105; p. 103160
• Main Authors: Endutkin, Anton V., Panferova, Elena P., Barmatov, Alexander E., Zharkov, Dmitry O.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-09-2021
• Subjects: 8-Oxoguanine; DNA damage; DNA glycosylases; DNA repair; GO system; Staphylococcus aureus; DNA glycosylases; GO system; DNA repair; DNA damage; Staphylococcus aureus; 8-Oxoguanine
• ISSN: 1568-7864; 1568-7856
• DOI: 10.1016/j.dnarep.2021.103160

•Fpg and MutY from S. aureus NCTC 8325 lab strain and Fpg from a multidrug-resistant C0673 isolate have been characterized.•Both Fpg homologs excise 8-oxoguanine with the highest efficiency, followed by 5-hydroxyuracil and 5,6-dihydrouracil.•S. aureus MutY has the same substrate specificity as E. coli MutY but might form different reaction intermediates.•All studied S. aureus enzymes complement the mutator phenotype of E. coli fpg mutY double knockout strains.•S. aureus seems to possess a functional GO system that could be targeted to sensitize this pathogen to oxidative stress.
GO system is part of base excision DNA repair and is required for the correct repair of 8-oxoguanine (8-oxoG), one of the most abundant oxidative lesions. Due to the ability of 8-oxoG to mispair with A, this base is highly mutagenic, and its repair requires two enzymes: Fpg that removes 8-oxoG from 8-oxoG:C pairs, and MutY that excises the normal A from 8-oxoG:A mispairs. Here we characterize the properties of putative GO system DNA glycosylases from Staphylococcus aureus, an important human opportunistic pathogen that causes hospital infections and presents a serious health concern due to quick spread of antibiotic-resistant strains. In addition to Fpg and MutY from the reference NCTC 8325 strain (SauFpg1 and SauMutY), we have also studied an Fpg homolog from a multidrug-resistant C0673 isolate (SauFpg2), which is different from SauFpg1 in its sequence. Both SauFpg enzymes showed the highest activity at pH 7.0–9.0 and NaCl concentrations 25–75 mM (SauFpg1) or 50–100 mM (SauFpg2), whereas SauMutY was active at a broad pH range and had a salt optimum at ∼75 mM NaCl. Both SauFpg1 and SauFpg2 bound and cleaved duplexes containing 8-oxoG, 5-hydroxyuracil, 5,6-dihydrouracil or apurinic/apyrimidinic site paired with C, T, or G, but not with A. For SauFpg1 and SauFpg2, 8-oxoG was the best substrate tested, and 5,6-dihydrouracil was the worst one. SauMutY efficiently excised adenine from duplex substrates containing A:8-oxoG or A:G pairs. SauFpg enzymes were readily trapped on DNA by NaBH4 treatment, indicating formation of a Schiff base reaction intermediate. Surprisingly, SauMutY was also trapped significantly better than its E. coli homolog. All three S. aureus GO glycosylases drastically reduced spontaneous mutagenesis when expressed in an fpg mutY E. coli double mutant. Overall, we conclude that S. aureus possesses an active GO system, which could possibly be targeted for sensitization of this pathogen to oxidative stress.