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3'-terminated Overhangs Regulate DNA Double-Strand Break Processing in Escherichia coli

Đermić, Edyta; Zahradka, Davor; Vujaklija, Dušica; Ivanković, Siniša; Đermić, Damir (2017) 3'-terminated Overhangs Regulate DNA Double-Strand Break Processing in Escherichia coli. G3-Genes Genomes Genetics, 7 (9). pp. 3091-3102. ISSN 2160-1836

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Double-strand breaks (DSBs) are lethal DNA lesions, which are repaired by homologous recombination in Escherichia coli To study DSB processing in vivo, we induced DSBs into the E. coli chromosome by gamma irradiation and measured chromosomal degradation. We show that the DNA degradation is regulated by RecA protein concentration and its rate of association with ssDNA. RecA decreased DNA degradation in wild- type, recB and recD strains, indicating that it is a general phenomenon in E. coli On the other hand, DNA degradation was greatly reduced and unaffected by RecA in the recB1080 mutant (which produces long overhangs) and in a strain devoid of four exonucleases that degrade a 3' tail (ssExos). 3'-5' ssExos deficiency is epistatic to RecA deficiency concerning DNA degradation, suggesting that bound RecA is shielding 3' tail from degradation by 3'-5' ssExos. Since 3'-tail preservation is common to all these situations, we infer that RecA polymerization constitutes a subset of mechanisms for preserving the integrity of 3' tails emanating from DSBs, along with 3' tail's massive length, or prevention of their degradation by inactivation of 3'-5' ssExos. Thus, we conclude that 3' overhangs are crucial in controlling the extent of DSB processing in E. coli This study suggests a regulatory mechanism for DSB processing in E. coli, wherein 3' tails impose a negative feedback loop on DSB processing reactions, specifically on helicase reloading onto dsDNA ends.

Item Type: Article
Uncontrolled Keywords: DNA degradation ; exonuclease activity ; RecA protein ; single-strand specific exonucleases ; recB1080 mutant
Subjects: NATURAL SCIENCES > 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
Rekombinacija, popravak DNA i očuvanje integriteta genoma: novi puteviZahradka, DavorIP-2013-11-2978HRZZ
Depositing User: Damir Đermić
Date Deposited: 09 Nov 2022 12:24
DOI: 10.1534/g3.117.043521

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