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Regulation of ssb Gene Expression in Escherichia coli

Feliciello, Isidoro; Đermić, Edyta; Malović, Helena; Ivanković, Siniša; Zahradka, Davor; Ljubić, Sven; Procino, Alfredo; Đermić, Damir (2022) Regulation of ssb Gene Expression in Escherichia coli. International journal of molecular sciences, 23 (18). ISSN 1422-0067

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: Bacterial SSB proteins, as well as their eukaryotic RPA analogues, are essential and ubiquitous. They avidly bind single-stranded DNA and regulate/coordinate its metabolism, hence enabling essential DNA processes such as replication, transcription, and repair. The prototypic Escherichia coli SSB protein is encoded by an ssb gene. Although the ssb gene promoters harbor an SOS box, multiple studies over several decades failed to elucidate whether ssb gene expression is inducible and SOS dependent. The SOS regulon is comprised of about 50 genes, whose transcription is coordinately induced under stress conditions. Using quantitative real-time PCR, we determined the ssb gene expression kinetics in UV- and γ-irradiated E. coli and revealed that ssb gene expression is elevated in irradiated cells in an SOS-dependent manner. Additionally, the expression of the sulA gene was determined to indicate the extent of SOS induction. In a mutant with a constitutively induced SOS regulon, the ssb gene was overexpressed in the absence of DNA damage. Furthermore, we measured ssb gene expression by droplet digital PCR during unaffected bacterial growth and revealed that ssb gene expression was equal in wild-type and SOS− bacteria, whereas sulA expression was higher in the former. This study thus reveals a complex pattern of ssb gene expression, which under stress conditions depends on the SOS regulon, whereas during normal bacterial growth it is unlinked to SOS induction. The E. coli ssb gene is SOS regulated in such a way that its basal expression is relatively high and can be increased only through stronger SOS induction. The remarkable SOS induction observed in undisturbed wild-type cells may challenge our notion of the physiological role of the SOS response in bacteria.

Item Type: Article
Uncontrolled Keywords: SOS induction ; basal ssb expression ; UV and gamma irradiation
Subjects: NATURAL SCIENCES > Biology
NATURAL SCIENCES > Biology > Biochemistry and Molecular Biology
NATURAL SCIENCES > Biology > Microbiology
NATURAL SCIENCES > Biology > Genetics, Evolution and Phylogenetics
Divisions: Division of Molecular Biology
Division of Molecular Medicine
Project titleProject leaderProject codeProject type
Regulacija popravka dvolančanog loma u genomu bakterije Escherichia coliĐermić, DamirIP-2019-04-3790HRZZ
Depositing User: Damir Đermić
Date Deposited: 07 Nov 2022 15:10
DOI: 10.3390/ijms231810917

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