Mismatch extension ability of yeast and human DNA polymerase eta
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Updated: Oct 10, 2026
Proofreading and DNA Repair Assay Using Single Nucleotide Extension and MALDI-TOF Mass Spectrometry Analysis
Published on: June 19, 2018
M T Washington1, R E Johnson, S Prakash
1Sealy Center for Molecular Science, University of Texas Medical Branch, Galveston, Texas 77555-1061, USA.
Abstract:
DNA polymerase eta (Poleta) functions in error-free replication of UV-damaged DNA, and in vitro it efficiently bypasses a cis-syn T-T dimer by incorporating two adenines opposite the lesion. Steady state kinetic studies have shown that both yeast and human Poleta are low-fidelity enzymes, and they misincorporate nucleotides with a frequency of 10(-2)-10(-3) on both undamaged and T-T dimer-containing DNA templates. To better understand the role of Poleta in error-free translesion DNA synthesis, here we examine the ability of Poleta to extend from base mismatches. We find that both yeast and human Poleta extend from mismatched base pairs with a frequency of approximately 10(-3) relative to matched base pairs. In the absence of efficient extension of mismatched primer termini, the ensuing dissociation of Poleta from DNA may favor the excision of mismatched nucleotides by a proofreading exonuclease. Thus, we expect DNA synthesis by Poleta to be more accurate than that predicted from the fidelity of nucleotide incorporation alone.
Insights
DNA polymerase eta (Poleta) accurately replicates UV-damaged DNA. While Poleta has low fidelity, its limited extension from mismatches suggests enhanced accuracy in DNA repair.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- DNA polymerase eta (Poleta) is crucial for error-free replication of UV-damaged DNA.
- Poleta bypasses UV-induced lesions like cis-syn T-T dimers by incorporating adenines.
- Kinetic studies reveal Poleta as a low-fidelity enzyme, misincorporating nucleotides frequently.
Purpose of the Study:
- To investigate the role of Poleta in error-free translesion DNA synthesis.
- To determine Poleta's ability to extend DNA synthesis from base mismatches.
Main Methods:
- Steady state kinetic studies were employed.
- Analysis of both yeast and human Poleta was performed.
- Examination of DNA extension from mismatched base pairs was conducted.
Main Results:
- Both yeast and human Poleta exhibit low fidelity, with misincorporation rates of 10(-2)-10(-3).
- Poleta extends from mismatched base pairs at a low frequency of approximately 10(-3) relative to matched base pairs.
- Inefficient extension from mismatches leads to Poleta dissociation from DNA.
Conclusions:
- Poleta's limited extension from mismatches may promote excision of errors by proofreading exonucleases.
- DNA synthesis accuracy by Poleta is expected to be higher than predicted by nucleotide incorporation fidelity alone.
- This mechanism contributes to the overall fidelity of DNA repair pathways.
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