ABSTRACT
This chapter describes repair reactions occurring in mammalian cells which have been investigated with the aid of cell-free preparations and for which evidence of the nature of the enzymatic reaction taking place has been obtained. It focuses on enzymes involved in the initial removal of abnormal deoxyribonucleic acid (DNA) bases and in the production of gaps in one strand of the DNA. The chapter discusses the results of comparisons with chromatin and naked DNA substrates with the enzymes. It explores two enzymes which have been purified less extensively but represent particularly efficient forms of DNA repair. The chapter describes transmethylase protein which catalyzes this reaction may be important in protection against carcinogenesis by alkylating agents and is subject to a variety of regulatory factors. It is concerned with the repair of alkylated bases in DNA. The major alkylated adenine formed by the in vivo interaction of simple alkylating agents with DNA is 3-alkyladenine.
