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 .