O6-methylguanine (O6-MeG) (O6-MeG)

The O6 position of guanine is a critical nucleophilic site within the DNA structure that serves as a primary target for alkylating chemotherapeutic agents. When this position is alkylated, most commonly forming O6-methylguanine (O6-MeG), it creates a potent pro-mutagenic and cytotoxic DNA lesion [1]. During DNA replication, O6-MeG preferentially pairs with thymine instead of cytosine, leading to permanent G:C to A:T transition mutations if not corrected [4]. The persistence of these lesions triggers the mismatch repair (MMR) pathway, which results in futile repair cycles, double-strand breaks, and eventual programmed cell death [2]. The cellular enzyme O6-methylguanine-DNA methyltransferase (MGMT) acts as a suicide protein to remove these alkyl groups, directly impacting the efficacy of drugs like temozolomide and dacarbazine [1, 4]. Consequently, the O6 position of guanine is a focal point for cancer therapy, where the balance between DNA damage induction and enzymatic repair determines clinical outcomes in diseases such as glioblastoma [2, 3].

Other names

O6-alkylguanineO6-guanine6-O-methylguanineO6-MeGO6-methylguanine DNA lesion

Alkylating agents covalently attach alkyl groups to the O6 position of guanine, creating O6-alkylguanine adducts. These adducts cause DNA mispairing with thymine, which triggers the mismatch repair (MMR) system, leading to double-strand breaks and apoptosis [1, 2, 4].