However , increased amounts of breaks seem to be associated with increased deletion rates , as shown by previous studies ( 18 , 31 ) , and our demonstration that in a lexA ( def ) mutant overexpressing the translesion polymerases , removal of 3 LexA-controlled endo-nucleases ( uvrB , uvrC , and cho ) causes both a reduction in deletion formation ( Fig. 3 ) and DNA breaks ( Fig .
To examine whether lack of all four translesion DNA polymerases affects expression of other LexA-controlled functions , we used real-time PCR to measure uvrB expression in a lexA ( def ) mutant and a lexA ( def ) mutant lacking all four tranlesion DNA polymerases .
The levels of uvrB mRNA were increased 3.5-to 6-fold in both strains as compared to a lexA1 strain ( Figure S1 a ) , implying that LexA-regulated genes were expressed as normal in the multiple polymerase mutant .