The genes encoding formamidopyrimidine and MutY DNA glycosylases in Escherichia coli are transcribed as part of complex operons

Escherichia coli formamidopyrimidine (Fpg) DNA glycosylase and MutY DNA gly cosylase are base excision repair proteins that work together to protect ce lls from the mutagenic effects of the commonly oxidized guanine product 7,8 -dihydro-8-oxoguanine. The genes encoding these proteins,fpg and mutY, are both cotranscribed as part of complex operons.fpg is the terminal gene in a n operon with the gene order radC, rpmB, rpmG, and fpg. This operon has tra nscription initiation sites upstream of radC, in the radC coding region, an d immediately upstream of fpg. There is a strong attenuator in the rpmG-fpg intergenic region and three transcription termination sites downstream of fpg, There is an additional site, in the radC-rpmB intergenic region, that corresponds either to a transcription initiation site or to an RNase E or R Nase III cleavage site, mutY is the first gene in an operon with the gene o rder mutY,yggX mltC, and nupG. This operon has transcription initiation sit es upstream of mutY, in the mutY coding region, and immediately upstream of nupG. There also appear to be attenuators in the yggX-mltC and mltC-nupG i ntergenic regions. The order of genes in these operons has been conserved o r partially conserved only in other closely related gram-negative bacteria, although it is not known whether the genes are cotranscribed in these othe r organisms.