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Updated: Sep 20, 2026

Nucleoside Triphosphates - From Synthesis to Biochemical Characterization
Published on: April 3, 2014
[Effect of 3' exonuclease activity of polymerase on extension of phosphorothioate-modified primers]
Zi-fen Guo1, Lin-ling Chen, Jia Zhang
1Department of Pharmacy and Pharmacology, Nanhua University, Hengyang, Hunan, 421001 PR China.
Objective:
To determine whether 3'phosphorothioate-modified-2 terminal mismatched primers can turn off DNA polymerization mediated by Exo(+) polymerase.
Methods:
Two-directional primer extension was performed using polymerase with and without 3' exonuclease activity. The effects of unmodified primers and 3' phosphorothioate-modified primers on primer extension were evaluated.
Results:
Exo(-) polymerase yielded products from matched and mismatched primers regardless of their modification. However, 3' phosphorothioate-modified primers with a single base mismatch at -2 position worked similarly to the terminal (-1) mismatched primers in triggering the novelly reported "off-switch" of Exo(+) polymerase.
Conclusion:
These data suggested that the "off-switch" can be of enormous application in the diagnosis of single gene diseases and in the association studies by single nucleotide polymorphism screening.
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