AUTHOR=Wurihan  , Gezi  , Brambilla Elisa , Wang Shuwen , Sun Hongwei , Fan Lifei , Shi Yixin , Sclavi Bianca , Morigen  

TITLE=DnaA and LexA Proteins Regulate Transcription of the uvrB Gene in Escherichia coli: The Role of DnaA in the Control of the SOS Regulon

JOURNAL=Frontiers in Microbiology

VOLUME=Volume 9 - 2018

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.01212

DOI=10.3389/fmicb.2018.01212

ISSN=1664-302X

ABSTRACT=The uvrB gene belongs to the SOS network, encoding a key component of the nucleotide excision repair. The uvrB promoter region contains three identified promoters with four LexA binding sites, one consensus and six potential DnaA binding sites. More than 3-fold increase in transcription of the chromosomal uvrB gene is observed in both ∆lexA ∆sulA cells and dnaAA345S cells, and 5-fold increase in ∆lexA ∆sulA dnaAA345S cells relative to the wild-type cells is shown. The full activity of the uvrB promoter requires both the uvrBp1-2 and uvrBp3 promoters and is repressed by both the DnaA and LexA proteins. LexA binds tightly to LexA-box1 at the uvrBp1-2 promoter region irrespective of the presence of DnaA and this binding is important for the control of the uvrBp1-2 promoter. DnaA and LexA however compete for binding to and regulation of the uvrBp3 promoter in which DnaA-box6 overlaps with LexA-box4 and the transcription control of uvrBp3 largely depends on DnaA-box6. Transcription of other SOS regulon genes, such as recN and dinJ, is also repressed by both DnaA and LexA. Interestingly, the absence of LexA in the presence of the DnaAA345S mutant leads to production of elongated cells with incomplete replication, aberrant nucleoids and slow growth. We propose that DnaA is a modulator for maintenance of genome integrity during the SOS response by limiting the expression of the SOS regulon.