How does the presence of 7-deazaguanine in DNA affect the ability of human TLS polymerases to bypass DNA-protein cross-links (DPCs)?
Label:chem
Topic
7-deazaguanine is a modified guanine base used in this study to create stable DNA-protein cross-links (DPCs) that mimic the lesions formed by antitumor nitrogen mustards. These lesions are typically labile and unsuitable for structural and biological studies. The study investigates the ability of human translesion synthesis (TLS) polymerases to bypass DPCs conjugated to the 7-deazaguanine position of DNA.
From: "Bypass of DNA-Protein Cross-links Conjugated to the 7-Deazaguanine Position of DNA by Translesion Synthesis Polymerases", JBC, Volume 291, Issue 45, November 2016, Pages 23589-23603
Answer
The presence of 7-deazaguanine in DNA allows for the creation of stable DPCs that can be used to study the bypass mechanism of TLS polymerases. Human TLS polymerases κ and ι can bypass small peptide DPCs (10-mer) conjugated to 7-deazaguanine with low efficiency but high fidelity, inserting the correct nucleotide (C) opposite the lesion. However, larger DPCs (23-mer peptides and full-length proteins) completely block DNA replication. The study suggests that the size of the peptide or protein conjugated to 7-deazaguanine is a critical factor in determining the ability of TLS polymerases to bypass these lesions.
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