Gene amplification affecting o-alkylguanine-dna alkyltransferase activity is not detected in nitrosourea resistant or sensitive human cell lines

An attempt was made to characterize the genetic regulation of the human DNA repair protein O⁶-alkylguanine-DNA alkyltransferase (AGT) in the absence of the cloned gene. Four human cell lines, differing in AGT activity from very proficient to essentially absent, were assayed for gene amplification as a possible mediator of the methylation repair phenotype (Mer+, AGT activity and MER-, no AGT activity) using in-gel DNA renaturation and G-banded karyotype analysis. The former technique allows subsequent analysis of amplification units and cloning of observed ampliled DNA fragments, a hopeful approach to the isolation of the human AGT gene. Within the sensitivities of the techniques, no correlation between AGT activity and gene amplification was observed in the four cell lines tested.