Apoptosis-like death, an extreme SOS response in Escherichia coli
Authors: Ariel Erental
Yoav Smith
Hanna Engelberg-Kulka
Ziva Kalderon
Ann Saada
Journal: mBio (2014)
Discipline: MICROBIOLOGY
Keywords: SOS response; DNA damage; recA-lexA genes; cell cycle arrest; DNA repair
Affiliations: Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada (IMRIC), The Hebrew University-Hadassah Medical School, Jerusalem, Israel., Monique and Jacques Robo Department of Genetic Research, Hadassah-Hebrew University Medical Center, Jerusalem, Israel, Department of Genetic and Metabolic Diseases, Hadassah-Hebrew University Medical Center, Jerusalem, Israel, Genomic Data Analysis Unit, The Hebrew University-Hadassah Medical School, The Hebrew University of Jerusalem, Jerusalem, Israel., Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada (IMRIC), The Hebrew University-Hadassah Medical School, Jerusalem, Israel .

Abstract:  In bacteria, SOS is a global response to DNA damage, mediated by the recA-lexA genes, resulting in cell cycle arrest, DNA repair, and mutagenesis. Previously, we reported that Escherichia coli responds to DNA damage via another recA-lexA-mediated pathway resulting in programmed cell death (PCD). We called it apoptosis-like death (ALD) because it is characterized by membrane depolarization and DNA fragmentation, which are hallmarks of eukaryotic mitochondrial apoptosis. Here, we show that ALD is an extreme SOS response that occurs only under conditions of severe DNA damage. Furthermore, we found that ALD is characterized by additional hallmarks of eukaryotic mitochondrial apoptosis, including (i) rRNA degradation by the endoribonuclease YbeY, (ii) upregulation of a unique set of genes that we called extensive-damage-induced (Edin) genes, (iii) a decrease in the activities of complexes I and II of the electron transport chain, and (iv) the formation of high levels of OH˙ through the Fenton reaction, eventually resulting in cell death. Our genetic and molecular studies on ALD provide additional insight for the evolution of mitochondria and the apoptotic pathway in eukaryotes. Importance: The SOS response is the first described and the most studied bacterial response to DNA damage. It is mediated by a set of two genes, recA-lexA, and it results in DNA repair and thereby in the survival of the bacterial culture. We have shown that Escherichia coli responds to DNA damage by an additional recA-lexA-mediated pathway resulting in an apoptosis-like death (ALD). Apoptosis is a mode of cell death that has previously been reported only in eukaryotes. We found that E. coli ALD is characterized by several hallmarks of eukaryotic mitochondrial apoptosis. Altogether, our results revealed that recA-lexA is a DNA damage response coordinator that permits two opposite responses: life, mediated by the SOS, and death, mediated by the ALD. The choice seems to be a function of the degree of DNA damage in the cell. 

Retracted: No

PubPeer comments:
 A corrigendum was published for this paper :  In the Western blot analysis experiment that appeared in Fig. 4 of the original paper, an incorrect panel for the u0394mazEFlexA3 strain was pasted into the figure during our editing process. We provide here a corrected Fig. 4 including the correct u0394mazEFlexA3 panel. Here is the original figure : ![file] , 
 Panels from Fig. 2 of this paper are very similar to those of Fig. 3 of a paper from the same authors previously published in PLoS Biol. . ![file] , 
 Some highlighted similarities between the previously mentionned panels (Left : 2014 mBio ; Right : 2012 PLoS Biol.) ![file] , 
 The highlighted panel from Fig. 6H appears more similar than expected to a panel from Figure S6B of a previous PLoS Biol. paper . Could the authors check ? ![file] ,