O6-alkylguanine DNA lesion (O6-alkG)

O6-alkylguanine lesions are specific DNA adducts formed by the covalent attachment of an alkyl group to the oxygen atom at the 6th position of the guanine base (Source: Mutation Research, 2000). These lesions are primarily generated by alkylating chemotherapeutic agents such as temozolomide and dacarbazine, which are used to treat various malignancies including glioblastoma and melanoma (Source: PubChem). If not repaired by the suicide enzyme O6-methylguanine-DNA methyltransferase (MGMT), the O6-alkylguanine base tends to mispair with thymine during DNA replication (Source: DNA Repair, 2007). This mismatch triggers the mismatch repair (MMR) pathway, which results in futile cycling, double-strand breaks, and ultimately, apoptosis (Source: Nature Reviews Cancer, 2004). Consequently, the presence and persistence of these lesions are critical for the cytotoxic efficacy of certain anticancer treatments (Source: Journal of Clinical Oncology). However, their mutagenic potential also poses a risk for secondary malignancies, and high levels of MGMT can lead to drug resistance by rapidly removing the lesions (Source: NEJM).

Other names

O6-methylguanineO6-MeGO6-alkyl-GO6-guanine DNA adduct

Alkylating agents transfer alkyl groups to the O6 position of guanine; the resulting lesion causes G:C to A:T transitions or triggers apoptosis via the mismatch repair system when paired with thymine.