It has been previously shown both in vivo and in vitro that DNA synthesis past an oxidatively damaged form of ganine, 7,8-dihydro-8-oxoguanine (8-oxoG) (3, 4). Recently, it has been shown that DNA synthesis past 8-oxoG can result in the misincorporation of adenine opposite the damaged guanine (5-7) and that inactivation of the mutM (_fpg) gene leads specifically to G-C T-A transversions (4, 8).In this paper we present evidence that Escherichia coli has, at least in the case ofthe 8-oxoG lesion, a third line ofdefense against oxidative damage to DNA. Unlike the first two forms of protection, which target the active oxygen species or the damage it inflicts on nucleic acids, this activity leads to the correction of errors that are induced by replication of templates containing 8-oxoG lesions. We find that MutY protein, originally identified as an adenine glycosylase active on A/G mispairs (9) MATERIALS AND METHODSOfigodeoxynucleotides. The 23-mer oligodeoxynucleotides, including the one containing the site-specific 8-oxoG lesion, were synthesized and purified as described (6,11). The purified oligomers (4 pmol) were 32P-labeled at the 5' terminus with 10 units of T4 polynucleotide kinase in the presence of 7 pmol of [P32P] ATP (6 Ci/humol; New England Nuclear; 1 Ci = 37 GBq) for 10 min at 370C. After heat inactivation at 900C for 7 min, the labeled primers were annealed with an excess of unlabeled complementary oligodeoxynucleotide at 900C in 50 mM NaCl for 2 min, cooled to room temperature, and then incubated on ice. The sequences of the oligodeoxynucleotides are shown below (nucleotides involved in mispair formation are underlined; GO,.

The rate of seroconversion 15 days after documented SARS-COV2 on RT-PCR was therefore significantly lower in cancer patients versus HCWs (30% versus 71%, P ¼ 0.04). Importantly, six of the seven serodiagnostic-negative cancer patients had received cytotoxic therapy or major surgical intervention in the previous 4 weeks, compared with none of the five remaining patients (P ¼ 0.003). None of these patients died.In this series, 5 of 85 (5.9%) and 13 of 244 (5.4%) cancer patients and HCWs, respectively, had detectable Ab against COVID-19. However, cancer patients had a significantly lower detection rate of SARS-COV2 Ab 15 days or later after symptoms and RT-PCRþ testing. Anti-SARS-COV2 Ab were more often undetectable in patients receiving cancer treatments in the month before testing. Additional studies will be needed to confirm whether immune response to the virus is influenced by recent cancer treatments.

The mutY gene of Escherichia coli, which codes for an adenine glycosylase that excises the adenine of a G-A mispair, has been cloned and sequenced. The mutY gene codes for a protein of 350 amino acids (Mr = 39,123) and the clone genetically complements the mutY strain. The protein shows significant sequence homology to E. coli endonuclease III, an enzyme that has previously been shown to have glycosylase activity on damaged base pairs. Sequence analysis suggests that, like endonuclease III, MutY is an iron-sulfur protein with a [4Fe-4S]2+ cluster.

We have cloned chromosomal DNA bordering an insert that inactivates mutM. Sequencing of this clone has revealed that the insertion element is located between the promoter and structural gene for formamidopyrimidine-DNA glycosylase (Fapy-DNA glycosylase). An overproducing clone of Fapy-DNA glycosylase complements the original mutM strain that had been isolated after EMS mutagenesis. Thus, we conclude that MutM is actually Fapy-DNA glycosylase. mutM has previously been characterized as a mutator strain that leads specifically to G.C----T.A transversions. This in vivo characterization correlates well with the mutagenic potential of one of the lesions Fapy-DNA glycosylase removes, 8-oxo-7,8-dihydro-2'-deoxyguanine (8-OxodG).