Escherichia coil,Saccharomyces cerevisiae, rat and human 3-methyladenine DNA glycosylases repair 1,N⁶-ethenoadenine when present in DNA

Abstract

The human carcinogen vinyl chloride is metabolized in the liver to reactive intermediates which generate various ethenobases in DNA. It has been reported that 1,N6-ethenoadenine (epsilon A) is excised by a DNA glycosylase present in human cell extracts, whereas protein extracts from Escherichia coli and yeast were devoid of such an activity. We confirm that the human 3-methyladenine-DNA glycosylase (ANPG protein) excises epsilon A residues. This finding was extended to the rat (ADPG protein). We show, at variance with the previous report, that pure E.coli 3-methyladenine-DNA glycosylase II (AlkA protein) as well as its yeast counterpart, the MAG protein, excise epsilon A from double stranded oligodeoxynucleotides that contain a single epsilon A. Both enzymes act as DNA glycosylases. The full length and the truncated human (ANPG 70 and 40 proteins, respectively) and the rat (ADPG protein) 3-methyladenine-DNA glycosylases activities towards epsilon A are 2-3 orders of magnitude more efficient than the E.coli or yeast enzyme for the removal of epsilon A. The Km of the various proteins were measured. They are 24, 200 and 800 nM for the ANPG, MAG and AlkA proteins respectively. These three proteins efficiently cleave duplex oligonucleotides containing epsilon A positioned opposite T, G, C or epsilon A. However the MAG protein excises A opposite cytosine much faster than opposite thymine, guanine or adenine.

Urinary level of 1,N6 ‐ethenodeoxyadenosine, a marker of oxidative stress, is associated with salt excretion and ω6‐polyunsaturated fatty acid intake in postmenopausal Japanese women

“…The main repair pathway of ⑀dA is via 3-methyladenine DNA glycosylase that excises this exocyclic DNA base. 22,23 However, additional (nucleotide excision) repair pathways may operate in vivo that may liberate this adduct as deoxynucleoside, but this remains to be demonstrated. 1 Intervention group, n ϭ 29; control group, n ϭ 26.-2 Difference between pre-and post-intervention, p Ͻ 0.001.…”

Accumulation of lipid peroxidation‐derived DNA lesions in iron‐overloaded thalassemic mouse livers: Comparison with levels in the lymphocytes of thalassemia patients

“…As shown in vitro, repair by base excision repair proteins for edA occurs at a faster rate than that for edC, [43][44][45] leading to different adduct levels remaining in tissue DNA. If a nucleotide excision repair pathway eliminates the 2 etheno lesions from tissue DNA with a similar higher preference for edA, one would expect an inverse relation of the repair products in urine as was found indeed in the patients' urine.…”

Repair of exocyclic DNA adducts: rings of complexity

“…The primary activity of these glycosylases, however, has generally been thought to remove N-3-and N-7-alkylated bases. Earlier Dosanjh et al (37) reported that eA is excised 10-to 20-fold more efficiently than 3mA by hANPG, whereas data from several other studies (28,38,39) showed that hANPG prefers 3mA over …”

“…(27) This was confirmed shortly afterwards by Laval's group using a purified recombinant hANPG. (28) In addition, they showed that eA is removed by hANPG homologs in rat, yeast and E. coli. These activities are evolutionarily enhanced inasmuch as the mammalian glycosylases excise eA two to three orders of magnitude more efficiently than their yeast and bacterial functional homologs.…”

“…These activities are evolutionarily enhanced inasmuch as the mammalian glycosylases excise eA two to three orders of magnitude more efficiently than their yeast and bacterial functional homologs. (28) Both opposite base (28)(29)(30) and sequence context (30,31) can affect the eA activity of ANPGs but data from various studies differed in the magnitude of such effects. Recently, it was reported that the E. coli mismatchspecific uracil-DNA glycosylase (Mug) could remove eA but with extremely low efficiency.…”