Ability of Pol IV mutants to tolerate MMS-induced DNA damage <i>in vivo</i>.

<p><b>(A)</b> The dependence of MMS-induced mutagenesis on Pol IV (<i>dinB</i>) and Pol V (<i>umuDC</i>) function using strains RW118, RW120 (Δ<i>umuDC</i>), VB102 (Δ<i>dinB</i>), and VB103 (Δ<i>dinB</i> Δ<i>umuDC</i>), and <b>(B)</b> the ability of ~4-fold higher than SOS-induced levels of wild type or mutant Pol IV proteins (expressed from a plasmid) to suppress the frequency of Pol V-dependent MMS-induced mutagenesis of strain RW118 by competing with Pol V was measured as described in <i>Materials and Methods</i> and [<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005507#pgen.1005507.ref033" target="_blank">33</a>]. Results represent the average of at least 4 independent experiments ± one standard deviation. Symbols are as follows: **, <i>p</i><0.0001; *, <i>p</i><0.05.