The Escherichia coli AlkB protein protects human cells against alkylation-induced toxicity.
Escherichia coli can ameliorate the toxic effects of alkylating agents either by preventing DNA alkylation or by repairing DNA alkylation damage. The alkylation-sensitive phenotype of E. coli alkB mutants marks the alkB pathway as an extremely effective defense mechanism against the cytotoxic effects of the SN2, but not the SN1, alkylating agents. Although it is clear that AlkB helps cells to better handle alkylated DNA, no DNA alkylation repair function could be assigned to the purified AlkB protein, suggesting that AlkB either acts as part of a complex or acts to regulate the expression of other genes whose products are directly responsible for alkylation resistance. However, here we present evidence that the provision of alkylation resistance is an intrinsic function of the AlkB protein per se. We expressed the E. coli AlkB protein in two human cell lines and found that it confers the same characteristic alkylation-resistant phenotype in this foreign environment as it does in E. coli. AlkB expression rendered human cells extremely resistant to cell killing by the SN2 but not the SN1 alkylating agents but did not affect the ability of dimethyl sulfate (an SN2 agent) to alkylate the genome. We infer that SN2 agents produce a class of DNA damage that is not efficiently produced by SN1 agents and that AlkB somehow prevents this damage from killing the cell.
Chen
B J
BJ
Harvard School of Public Health, Boston, Massachusetts 02115.
Carroll
P
P
Samson
L
L
D000071498:AlkB Homolog 1, Histone H2a Dioxygenase; D000477:Alkylating Agents / Q000494:pharmacology*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D004249:DNA Damage; D004260:DNA Repair; D045643:DNA Repair Enzymes; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins; D006367:HeLa Cells; D006801:Humans; D008770:Methylnitrosourea / Q000494:pharmacology; D006899:Mixed Function Oxygenases; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000096:biosynthesis; D013463:Sulfuric Acid Esters / Q000494:pharmacology; D014162:Transfection
D000477:Alkylating Agents; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D011994:Recombinant Proteins; D013463:Sulfuric Acid Esters; D008770:Methylnitrosourea; D006899:Mixed Function Oxygenases; C466427:AlkB protein, E coli; C499236:ALKBH1 protein, human; D000071498:AlkB Homolog 1, Histone H2a Dioxygenase; D045643:DNA Repair Enzymes; C007482:dimethyl sulfate