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Updated: May 27, 2026

Proofreading and DNA Repair Assay Using Single Nucleotide Extension and MALDI-TOF Mass Spectrometry Analysis
Published on: June 19, 2018
A new proofreading mechanism for lesion bypass by DNA polymerase-λ
Emmanuele Crespan1, Giovanni Maga, Ulrich Hübscher
1Institute of Molecular Genetics IGM-CNR, via Abbiategrasso 207, I-27100 Pavia, Italy.
Abstract:
Replicative DNA polymerases (DNA pols) increase their fidelity by removing misincorporated nucleotides with their 3' → 5' exonuclease activity. Exonuclease activity reduces translesion synthesis (TLS) efficiency and TLS DNA pols lack 3' → 5' exonuclease activity. Here we show that physiological concentrations of pyrophosphate (PP(i)) activate the pyrophosphorolytic activity by DNA pol-λ, allowing the preferential excision of the incorrectly incorporated A opposite a 7,8-dihydro-8-oxoguanine lesion, or T opposite a 6-methyl-guanine, with respect to the correct C. This is the first example of an alternative proofreading mechanism used during TLS.
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