On the fidelity of dna polymerase α: The influence of α-thio dntps, mn2+and mismatch repair

Abstract

The X174aml6 revertant system has been used to investigate the influence of thio-dNTPs and of Mn2+on the fidelity of the 9S DNA polymerase from calf thymus. Upon substituting dGTP by thio-dGTP during the in vitro replication, a nearly tenfold decrease in the frequency of G: G and G: T mispairs is observed. The formation of all other mispairs is not changed in the presence of the corresponding thio-dNTP. Mn2+at concentrations of 0.5 mM does not influence the frequencies of the mispairs. The expression rate of errors formed during in vitro replication in the (-) strand has been determined for all mispairs detectable in the Xaml6 system. The (-) strand expression of G: T, T: T and C: T mismatches is about 50% whereas for A: G, G: G and C: A mismatches it is clearly below 50%. We conclude that the different base-base mismatches are repaired with different efficiencies. © IRL Press Limited.