Repair in Escherichia coli alkB mutants of abasic sites and 3-methyladenine residues in DNA.

Escherichia coli alkB mutants are sensitive to methyl methanesulfonate and dimethylsulphate, and are defective in the processing of methylated DNA. The function of the AlkB protein has not been determined. Here, we show that alkB mutants are not defective in repairing several different types of potentially toxic DNA lesions that are known to be generated by MMS, including apyrimidinic and apurinic sites, and secondary lesions that could arise at these sites (DNA-protein cross-links and DNA interstrand cross-links). Also, alkB mutants were not sensitive to MeOSO2-(CH2)2-Lex, a compound that alkylates the minor groove of DNA generating primarily 3-methyladenine.