DNA N7-guanine (N7-G) (N7-G)

The N7 position of guanine is the most nucleophilic site within the DNA double helix and is located in the major groove, making it highly accessible to electrophilic chemical species (Hemminki, 1993). It serves as a critical molecular target for several classes of anticancer drugs, including platinum-based agents like cisplatin and various alkylating agents (Jamieson & Lippard, 1999). When these drugs bind to the N7 position, they form stable covalent adducts that can result in DNA cross-linking, either within the same strand or between opposing strands (Lawley & Phillips, 1996). These structural distortions physically block the progression of DNA polymerase and RNA polymerase, thereby inhibiting DNA replication and gene transcription (Colvin, 2003). The resulting DNA damage, if left unrepaired by cellular pathways such as nucleotide excision repair, activates signaling cascades that lead to cell cycle arrest and apoptosis, particularly in rapidly dividing malignant cells (Siddik, 2003).

Other names

Guanine N7 positionN7-deoxyguanosineN7-alkylguanineN7-G siteN7-position of guanine in DNA

Covalent binding of electrophilic drug metabolites to the nucleophilic N7 position of guanine bases, leading to the formation of DNA adducts, intrastrand cross-links, or interstrand cross-links that inhibit DNA synthesis and transcription, triggering apoptosis (Jamieson & Lippard, 1999; Colvin, 2003).