Methods of assaying DNA-repairing enzymes and their alkylated derivatives

Abstract

The present invention provides methods of assaying the human DNA repair enzyme O.sup.6 -methylguanine-DNA methyltransferase (MGMT) and/or active site alkylated derivatives thereof (R-MGMT), which rely on the ability of a protease, e.g., V8 Protease (also referred to as Glu-C Protease), to distinguish between these two enzyme forms. Such a method comprises the steps of: (a) contacting the sample with a protease to which one of human MGMT and R-MGMT is preferentially sensitive; and (b) determining whether the treated sample contains one or more polypeptides selected from (I) at least one polypeptide fragment characteristic of action of the protease on the protease-sensitive form of human MGMT and (ii) the protease-resistant form of human MGMT.