Disease relevance of Alkylation

• When Escherichia coli is chronically exposed to very low, nontoxic doses of a monofunctional alkylating agent (notably N-methyl-N'-nitro-nitrosoguanidine, MNNG), the adaptive DNA repair pathway is induced which enables the bacteria to resist the killing and mutagenic effects of further alkylation damage [1].
• Because particle integrity was not affected by selective alkylation (as shown by electron microscopy and sucrose gradient experiments), it was reasoned that the dynamic nature of the viral capsid acts as a conduit to the interior of the particle [2].
• Others, such as ovalbumin, fetuin, bromelain, ovomucoid, alpha 1-acid glycoprotein, immunoglobulin G, and influenza virus hemagglutinin became susceptible only after reduction and alkylation or when cleavage was performed in the presence of 1% 2-mercaptoethanol [3].
• Thus, the abolition of the toxicity of extracellularly applied botulinum neurotoxin A by the cleavage of both disulfides, and the alkylation of the half-cystines involved, results from ineffective uptake [4].
• Affinity alkylation of the Trp-B4 residue of the beta -subunit of the glutaryl 7-aminocephalosporanic acid acylase of Pseudomonas sp. 130 [5].

High impact information on Alkylation

• O6-methylguanine-DNA methyltransferase directly reverses some simple alkylation adducts [6].
• The human enzyme 3-methyladenine DNA glycosylase removes a diverse group of damaged bases from DNA, including cytotoxic and mutagenic alkylation adducts of purines [7].
• The binding of DNA to gyrase confers no protection against alkylation of the DNA by dimethyl sulfate [8].
• Here we report that, under conditions favouring the H-form extrusion, guanines of the 3' half of the purine strand are protected against alkylation by dimethylsulphate, whereas adenines of the 5' half of the purine strand react with diethyl pyrocarbonate [9].
• On alkylation of DNA by chemical carcinogens such as dimethyl sulphate, methyl methanesulphonate, methylnitrosourea or methylnitrosoguanidine, the main target is the N7 of the guanosine residue, yielding 7-methylguanine (mG) [10].

Chemical compound and disease context of Alkylation

• In wild-type E. coli the adaptive response began to contribute to O6-methylguanine repair about one hour after alkylation, the time required for the full induction of the ada DNA methyltransferase [11].
• The binding of ribosomal protein L18 affects specific nucleotides in Escherichia coli 5S RNA as detected by dimethyl sulfate alkylation and RNase A digestion of the 5S-L18 complex [12].
• When expressed in a baculovirus system, recombinant VWF CK domains (residues 1957-2050) were secreted as dimers that were converted to monomers by selective reduction and alkylation of three unconserved cysteine residues: Cys(2008), Cys(2010), and Cys(2048) [13].
• The binding of catabolite activator protein and RNA polymerase to the Escherichia coli galactose and lactose promoters probed by alkylation interference studies [14].
• The structure of lipid A from the lipopolysaccharide of Rhizobium leguminosarum bv. phaseoli (wild type strain CE3) was investigated by alkylation analysis, nuclear magnetic resonance spectroscopy, and electrospray and fast atom bombardment mass spectrometry of the de-O-acylated lipid A [15].

Biological context of Alkylation

• We now show that the chronic treatment of a Chinese hamster ovary (CHO) and a SV40-transformed human skin fibroblast (GM637) cell line with non-toxic levels of MNNG renders the cells resistant to the induction of sister chromatid exchange (SCE) by further alkylation damage [1].
• Binding of alpha-bungarotoxin is to the physiologically relevant acetylcholine binding site as defined by affinity ligand alkylation [16].
• The specific inhibition of O6-methylguanine formation only in double-stranded DNA and the relatively low inhibition of 7-methylguanine formation rule out the possibility that ellagic acid prevents DNA alkylation by scavenging the electrophilic intermediate generated in the hydrolysis of MeNU [17].
• These results suggest the importance of thymidine alkylation in ENU-induced mutagenesis in vivo [18].
• Because thermal treatment of (N7 guanine)-DNA adducts leads to DNA strand breakage, we were able to determine the site of alkylation of psorospermin within the topoisomerase II gate site and infer that intercalation takes place at the gate site between base pairs at the +1 and +2 positions [19].

Anatomical context of Alkylation

• The labeling of fragments with alpha-bungarotoxin could be inhibited by prior affinity alkylation of receptor-containing membranes with 4-(N-maleimido)-alpha-benzyltrimethylammonium iodide [20].
• The essential role of Secys in TR isolated from HeLa cells was demonstrated by the alkylation studies [21].
• The quantitative alkylation of bone marrow DNA by chlorozotocin, 22.8 +/- 1.2 pmole/mg DNA, was equivalent to that produced by CCNU, 22.9 +/- 0.5 pmole/mg DNA [22].
• These results support the possibility that alkylation of liver cells would not be confined to those cells metabolizing dimethylnitrosamine but could be extended to those cells which are in close proximity to the activating cells [23].
• The initial level of 7-methylguanine, 3-methyladenine, and O6-methylguanine formation and the repair rates for these alkylated bases were the same in the resistant and in the parental cell line, indicating that the resistance to alkylation damage is not due to differences in DNA alkylation [24].

Associations of Alkylation with chemical compounds

• One of the principal mechanisms thought to be involved in initiating carcinogenesis is the alkylation of specific sites on DNA, such as the O(6) position of guanine [25].
• Alkylation of the more strongly nucleophilic ring nitrogen atoms of the purine bases, which is the main site of reaction with all these agents, appears to be much less important in alkylation carcinogenesis [26].
• Therefore, we decided to investigate the alkylation and repair of O(6)-and 7-methylguanine in the target and non-target cells following oral administration of 1,2-dimethylhydrazine [25].
• Irradiation of DNA with UV light or alkylation with N-acetoxyacetylaminofluorene (AAAF) shifts the transition to lower salt concentrations [27].
• Pulmonary bronchiolar alkylation and necrosis by 3-methylfuran, a naturally occurring potential atmospheric contaminant [28].

Gene context of Alkylation

• In these, but not in NR1-NR2A, the DTT effect was rendered insensitive to reoxidation by alkylation [29].
• MGT1 transcript levels are not increased in response to DNA alkylation damage, nor is the MGT1 MTase involved in the regulation of the yeast 3-methyladenine DNA glycosylase gene (MAG) [30].
• The NH(2)- and COOH-terminal Stat domains are generally dispensable, whereas alkylation of a single cysteine residue blocked cytokine-independent nuclear translocation and thus implicated the linker domain into the cycling of Stat1 [31].
• This was done with iodide (anion binding) and bromopyruvic acid (alkylation), and the respective assays evaluated as diagnostic tools for CA II deficiency in human red cells [32].
• The apparent Km values for addition of GalNAc to oligosaccharides on hCG alpha and hCG beta, 13.0 and 6.2 microM, respectively, are not altered by reduction and alkylation [33].

Analytical, diagnostic and therapeutic context of Alkylation

• Human O(6)-alkylguanine-DNA alkyltransferase (AGT), which directly reverses endogenous alkylation at the O(6)-position of guanine, confers resistance to alkylation chemotherapies and is therefore an active anticancer drug target [34].
• Upon reduction and alkylation, the antigen-binding GIF dissociated into a 62- to 64-kDa protein which gave positive ELISA with antibody 110BH3 but no signal with antibody 388F1, and a 15-kDa protein, which gave ELISA signal with the 388F1 but not with 110BH3 [35].
• DNA alkylation was essential for the formation of top1-mediated cleavage complexes by Et743, and the distribution of the drug-induced top1 sites was different for Et743 and camptothecin. top1-DNA complexes were also detected in Et743-treated CEM cells by using cesium chloride gradient centrifugation followed by top1 immunoblotting [36].
• Flow cytometry indicated that in vivo alkylation resistance in Aag null BM cells may be restricted to cells of the myeloid lineage [37].
• Circular dichroism studies of the ethylene adduct and of the ring D regioisomer of N-ethylprotoporphyrin IX obtained by alkylation of the prosthetic heme of hemoglobin have been used to determine which face of cytochrome P-450 heme is alkylated by the unsaturated substrates [38].

References