Chromosome Segregation and Cell Division Defects in Escherichia coli Recombination Mutants Exposed to Different DNA-Damaging Treatments

Zahradka, Ksenija; Repar, Jelena; Đermić, Damir; Zahradka, Davor (2023) Chromosome Segregation and Cell Division Defects in Escherichia coli Recombination Mutants Exposed to Different DNA-Damaging Treatments. Microorganisms, 11 (3). ISSN 2076-2607

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Official URL: https://www.mdpi.com/2076-2607/11/3/701

Abstract

Homologous recombination repairs potentially lethal DNA lesions such as double-strand DNA breaks (DSBs) and single-strand DNA gaps (SSGs). In Escherichia coli, DSB repair is initiated by the RecBCD enzyme that resects double-strand DNA ends and loads RecA recombinase to the emerging single-strand (ss) DNA tails. SSG repair is mediated by the RecFOR protein complex that loads RecA onto the ssDNA segment of gaped duplex. In both repair pathways, RecA catalyses reactions of homologous DNA pairing and strand exchange, while RuvABC complex and RecG helicase process recombination intermediates. In this work, we have characterised cytological changes in various recombination mutants of E. coli after three different DNA-damaging treatments: (i) expression of I-SceI endonuclease, (ii) gamma-irradiation, and (iii) UV-irradiation. All three treatments caused severe chromosome segregation defects and DNA-less cell formation in the ruvABC, recG, and ruvABC recG mutants. After I-SceI expression and gamma-irradiation, this phenotype was efficiently suppressed by the recB mutation, indicating that cytological defects result mostly from incomplete DSB repair. In UV-irradiated cells, the recB mutation abolished cytological defects of recG mutants and also partially suppressed the cytological defects of ruvABC recG mutants. However, neither recB nor recO mutation alone could suppress the cytological defects of UV- irradiated ruvABC mutants. The suppression was achieved only by simultaneous inactivation of the recB and recO genes. Cell survival and microscopic analysis suggest that chromosome segregation defects in UV-irradiated ruvABC mutants largely result from defective processing of stalled replication forks. The results of this study show that chromosome morphology is a valuable marker in genetic analyses of recombinational repair in E. coli.

Item Type:

Article

Uncontrolled Keywords:

recombination pathways ; DNA repair ; double-strand breaks ; single-strand gaps ; RecBCD ; RecFOR ; RuvABC ; RecG ; chromosome segregation defects ; stalled replication forks

Subjects:

NATURAL SCIENCES > Biology

Divisions:

Division of Molecular Biology

Projects:

Project title	Project leader	Project code	Project type
Rekombinacija, popravak DNA i očuvanje integriteta genoma: novi putevi	Zahradka, Davor	IP-2013-11-2978	HRZZ
Regulacija popravka dvolančanog loma u genomu bakterije Escherichia coli	Đermić, Damir	IP-2019-04-3790	HRZZ

Depositing User:

Ksenija Zahradka

Date Deposited:

20 Jun 2023 13:09

URI:

http://fulir.irb.hr/id/eprint/8043

DOI:

10.3390/microorganisms11030701