biostudies-literatureGu CNCI NIH HHS3693-704https://www.ebi.ac.uk/biostudies/studies/S-EPMC1920245biostudies-literatureUnknown35(11)The cytotoxic effects of thiopurine drugs are mostly exerted through the formation of thioguanine nucleotide and its subsequent incorporation into DNA. The 6-thioguanine (6-TG) in DNA can be converted to S6-methylthio-2-aminopurine (2-AP-6-SCH3) and 2-aminopurine-6-sulfonic acid (2-AP-6-SO3H) upon reaction with S-adenosyl-L-methionine and irradiation with UVA light, respectively. Here we prepared oligodeoxynucleotides (ODNs) harboring a 6-TG, 2-AP-6-SCH3 or 2-AP-6-SO3H at a defined site and examined, by using LC-MS/MS, the in vitro replication of these substrates with yeast polymerase eta and Klenow fragment (KF-). Our results revealed that 2-AP-6-SCH3 could be bypassed by KF-, with significant misincorporation of thymine opposite the lesion. The 2-AP-6-SO3H, however, blocked markedly the Nucleic acids researchIn vitro replication and thermodynamic studies of methylation and oxidation modifications of 6-thioguanine.PMC1920245R01 CA096906R01 CA96906R01 CA101864Gu CWang YfalseIn vitro replication and thermodynamic studies of methylation and oxidation modifications of 6-thioguanine.The cytotoxic effects of thiopurine drugs are mostly exerted through the formation of thioguanine nucleotide and its subsequent incorporation into DNA. The 6-thioguanine (6-TG) in DNA can be converted to S6-methylthio-2-aminopurine (2-AP-6-SCH3) and 2-aminopurine-6-sulfonic acid (2-AP-6-SO3H) upon reaction with S-adenosyl-L-methionine and irradiation with UVA light, respectively. Here we prepared oligodeoxynucleotides (ODNs) harboring a 6-TG, 2-AP-6-SCH3 or 2-AP-6-SO3H at a defined site and examined, by using LC-MS/MS, the in vitro replication of these substrates with yeast polymerase eta and Klenow fragment (KF-). Our results revealed that 2-AP-6-SCH3 could be bypassed by KF-, with significant misincorporation of thymine opposite the lesion. The 2-AP-6-SO3H, however, blocked markedly the 2007-01-01T00:00:00Z20072025-04-26T02:20:13.233Z2019-03-27T02:04:22ZS-EPMC19202451751778610.1093/nar/gkm247