Oxidative DNA adducts and DNA-protein cross-links are the major DNA lesions induced by arsenite.

Abstract

Arsenic is recognized to be a nonmutagenic carcinogen because it induces DNA damage only at very high concentrations. However, many more DNA strand breaks could be detected by digesting the DNA of arsenite-treated cells with endonuclease III, formamidopyrimidine-DNA glycosylase, and proteinase K. By doing so, arsenite could be shown to induce DNA damage in human cells within a pathologically meaningful concentration range. Oxidized guanine products were detected in all arsenite-treated human cells examined. DNA-protein cross-links were also detected in arsenite-treated NB4 and HL60 cells. In human umbilical vein endothelial cells, the induction of oxidized guanine products by arsenite was sensitive to inhibitors of nitric oxide (NO) synthase but not to oxidant modulators, whereas the opposite result was obtained in vascular smooth muscle cells. On the other hand, the arsenite-induced oxidized guanine products and DNA-protein cross-links in NB4 and HL60 cells were sensitive to modulators of calcium, NO synthase, oxidant, and myeloperoxidase. Therefore, although oxidized guanine products were detected in all the human cells treated with arsenite, the pathways could be different in different cell types. Because the sensitivity and the mechanism of arsenic intoxication are cell specific, it is important that target tissues and target cells are used for investigations. It is also important that pathologically or pharmacologically meaningful concentrations of arsenic are used. This is because in most cases we are dealing with the chronic effect rather than acute toxicity.

Error-prone Translesion Synthesis Past DNA-Peptide Cross-links Conjugated to the Major Groove of DNA via C5 of Thymidine

“…However, previous studies were conducted with model DPCs containing peptides conjugated to various positions within purine nucleobases of DNA (the N 6 of adenine and the N 2 of guanine), and no information is available on polymerase bypass of the corresponding lesions involving pyrimidine residues in DNA. Such lesions can be generated upon exposure to endogenous free radicals, UV light, and ionizing radiation (32)(33)(34)(35)(36). Furthermore, irreversible trapping of DNA methyltransferases on genomic DNA can form DPCs at the C6 position of cytosine in DNA (30,31).…”

“…The transient protein-DNA intermediate can be irreversibly trapped in the presence of antitumor DNA methyltransferase inhibitors such as aza-dC (30,31). Furthermore, reactive oxygen species formed endogenously and induced by ionizing radiation can also cause protein cross-linking to the C5 and the C6 positions of pyrimidine bases on DNA (32)(33)(34)(35)(36).…”

“…This approach generates covalent conjugates between the C5 position of thymine in DNA and azide-functionalized polypeptides (Scheme 1). The resulting conjugates are structurally related to DPCs induced by reactive oxygen species (32)(33)(34)(35)(36)38). Our preliminary polymerase bypass studies with substrates containing site-specific C5-dT conjugates to polypeptides of increasing size (a 10-mer, 23-mer, and a 28.4-kDa protein) have revealed that although DPC lesions containing larger polypeptides completely blocked replication, 10-mer peptide conjugates were bypassed by hpol and (37).…”

EGF receptor-dependent JNK activation is involved in arsenite-induced p21Cip1/Waf1 upregulation and endothelial apoptosis

“…Indeed, very low physiologically relevant doses of arsenite induce DNA strand breaks and DNA-protein cross-links in a variety of cell types (2,29). Increasing evidence now links oncogenes and tumor suppressors such as Ras and p53, typically associated with carcinogenesis, with vascular disease (13,23).…”

Bypass of DNA-Protein Cross-links Conjugated to the 7-Deazaguanine Position of DNA by Translesion Synthesis Polymerases

“…Specifically, common chemotherapeutics such as nitrogen mustards, platinum compounds, and alkylnitrosoureas (3,4,8); environmental carcinogens such as formaldehyde and 1,3-butadiene (5, 9, 10); toxic metals (11)(12)(13); nitric oxide (14); free radicals (15,16); UV light (17); and ionizing radiation (6) mediate the formation of covalent DNAprotein cross-links (DPCs). 3 Mass spectrometry-based proteomic studies have identified a large number of cellular proteins that participate in DPC formation in cells treated with cross-linking agents, including DNA repair proteins, DNA polymerases, transcription factors, and structural proteins such as histones, heat shock proteins, and tubulins (3-6, 8, 10).…”