scholarly journals Comparison of Responses to Double-Strand Breaks between Escherichia coli and Bacillus subtilis Reveals Different Requirements for SOS Induction

2008 ◽  
Vol 191 (4) ◽  
pp. 1152-1161 ◽  
Author(s):  
Lyle A. Simmons ◽  
Alexi I. Goranov ◽  
Hajime Kobayashi ◽  
Bryan W. Davies ◽  
Daniel S. Yuan ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Bacillus Subtilis ◽  
Ionizing Radiation ◽  
Strand Break ◽  
Double Strand Break ◽  
Double Strand Breaks ◽  
Double Strand Break Repair ◽  
Strand Breaks ◽  
E Coli ◽  
Sos Induction

ABSTRACT DNA double-strand breaks are particularly deleterious lesions that can lead to genomic instability and cell death. We investigated the SOS response to double-strand breaks in both Escherichia coli and Bacillus subtilis. In E. coli, double-strand breaks induced by ionizing radiation resulted in SOS induction in virtually every cell. E. coli strains incapable of SOS induction were sensitive to ionizing radiation. In striking contrast, we found that in B. subtilis both ionizing radiation and a site-specific double-strand break causes induction of prophage PBSX and SOS gene expression in only a small subpopulation of cells. These results show that double-strand breaks provoke global SOS induction in E. coli but not in B. subtilis. Remarkably, RecA-GFP focus formation was nearly identical following ionizing radiation challenge in both E. coli and B. subtilis, demonstrating that formation of RecA-GFP foci occurs in response to double-strand breaks but does not require or result in SOS induction in B. subtilis. Furthermore, we found that B. subtilis cells incapable of inducing SOS had near wild-type levels of survival in response to ionizing radiation. Moreover, B. subtilis RecN contributes to maintaining low levels of SOS induction during double-strand break repair. Thus, we found that the contribution of SOS induction to double-strand break repair differs substantially between E. coli and B. subtilis.

scholarly journals Role of RAD52 Epistasis Group Genes in Homologous Recombination and Double-Strand Break Repair

2002 ◽  
Vol 66 (4) ◽  
pp. 630-670 ◽  
Author(s):  
Lorraine S. Symington
Keyword(s):  
Homologous Recombination ◽  
Ionizing Radiation ◽  
Strand Break ◽  
Double Strand Break ◽  
Dna Lesions ◽  
Double Strand Breaks ◽  
Double Strand Break Repair ◽  
Repair Pathway ◽  
Strand Breaks ◽  
Break Repair

SUMMARY The process of homologous recombination is a major DNA repair pathway that operates on DNA double-strand breaks, and possibly other kinds of DNA lesions, to promote error-free repair. Central to the process of homologous recombination are the RAD52 group genes (RAD50, RAD51, RAD52, RAD54, RDH54/TID1, RAD55, RAD57, RAD59, MRE11, and XRS2), most of which were identified by their requirement for the repair of ionizing-radiation-induced DNA damage in Saccharomyces cerevisiae. The Rad52 group proteins are highly conserved among eukaryotes, and Rad51, Mre11, and Rad50 are also conserved in prokaryotes and archaea. Recent studies showing defects in homologous recombination and double-strand break repair in several human cancer-prone syndromes have emphasized the importance of this repair pathway in maintaining genome integrity. Although sensitivity to ionizing radiation is a universal feature of rad52 group mutants, the mutants show considerable heterogeneity in different assays for recombinational repair of double-strand breaks and spontaneous mitotic recombination. Herein, I provide an overview of recent biochemical and structural analyses of the Rad52 group proteins and discuss how this information can be incorporated into genetic studies of recombination.

scholarly journals Repair System for Noncanonical Purines in Escherichia coli

2003 ◽  
Vol 185 (10) ◽  
pp. 3101-3110 ◽  
Author(s):  
Nicholas E. Burgis ◽  
Jason J. Brucker ◽  
Richard P. Cunningham
Keyword(s):  
Escherichia Coli ◽  
Strand Break ◽  
Double Strand Breaks ◽  
Repair System ◽  
Purine Base ◽  
Strand Breaks ◽  
E Coli ◽  
Endonuclease V ◽  
Sos Induction ◽  
Deoxynucleotide Triphosphate

ABSTRACT Exposure of Escherichia coli strains deficient in molybdopterin biosynthesis (moa) to the purine base N-6-hydroxylaminopurine (HAP) is mutagenic and toxic. We show that moa mutants exposed to HAP also exhibit elevated mutagenesis, a hyperrecombination phenotype, and increased SOS induction. The E. coli rdgB gene encodes a protein homologous to a deoxyribonucleotide triphosphate pyrophosphatase from Methanococcus jannaschii that shows a preference for purine base analogs. moa rdgB mutants are extremely sensitive to killing by HAP and exhibit increased mutagenesis, recombination, and SOS induction upon HAP exposure. Disruption of the endonuclease V gene, nfi, rescues the HAP sensitivity displayed by moa and moa rdgB mutants and reduces the level of recombination and SOS induction, but it increases the level of mutagenesis. Our results suggest that endonuclease V incision of DNA containing HAP leads to increased recombination and SOS induction and even cell death. Double-strand break repair mutants display an increase in HAP sensitivity, which can be reversed by an nfi mutation. This suggests that cell killing may result from an increase in double-strand breaks generated when replication forks encounter endonuclease V-nicked DNA. We propose a pathway for the removal of HAP from purine pools, from deoxynucleotide triphosphate pools, and from DNA, and we suggest a general model for excluding purine base analogs from DNA. The system for HAP removal consists of a molybdoenzyme, thought to detoxify HAP, a deoxyribonucleotide triphosphate pyrophosphatase that removes noncanonical deoxyribonucleotide triphosphates from replication precursor pools, and an endonuclease that initiates the removal of HAP from DNA.

scholarly journals T7 Single Strand DNA Binding Protein but Not T7 Helicase Is Required for DNA Double Strand Break Repair

2001 ◽  
Vol 183 (6) ◽  
pp. 1862-1869 ◽  
Author(s):  
Man Yu ◽  
Warren Masker
Keyword(s):  
Strand Break ◽  
Double Strand Break ◽  
Double Strand Breaks ◽  
Double Strand Break Repair ◽  
In Vitro System ◽  
Strand Breaks ◽  
E Coli ◽  
Break Repair ◽  
Gene 4

ABSTRACT An in vitro system based on Escherichia coliinfected with bacteriophage T7 was used to test for involvement of host and phage recombination proteins in the repair of double strand breaks in the T7 genome. Double strand breaks were placed in a uniqueXhoI site located approximately 17% from the left end of the T7 genome. In one assay, repair of these breaks was followed by packaging DNA recovered from repair reactions and determining the yield of infective phage. In a second assay, the product of the reactions was visualized after electrophoresis to estimate the extent to which the double strand breaks had been closed. Earlier work demonstrated that in this system double strand break repair takes place via incorporation of a patch of DNA into a gap formed at the break site. In the present study, it was found that extracts prepared from uninfected E. coli were unable to repair broken T7 genomes in this in vitro system, thus implying that phage rather than host enzymes are the primary participants in the predominant repair mechanism. Extracts prepared from an E. coli recA mutant were as capable of double strand break repair as extracts from a wild-type host, arguing that the E. coli recombinase is not essential to the recombinational events required for double strand break repair. In T7 strand exchange during recombination is mediated by the combined action of the helicase encoded by gene 4 and the annealing function of the gene 2.5 single strand binding protein. Although a deficiency in the gene 2.5 protein blocked double strand break repair, a gene 4 deficiency had no effect. This argues that a strand transfer step is not required during recombinational repair of double strand breaks in T7 but that the ability of the gene 2.5 protein to facilitate annealing of complementary single strands of DNA is critical to repair of double strand breaks in T7.

scholarly journals Single-molecule live-cell imaging reveals RecB-dependent function of DNA polymerase IV in double strand break repair

2020 ◽  
Vol 48 (15) ◽  
pp. 8490-8508 ◽  
Author(s):  
Sarah S Henrikus ◽  
Camille Henry ◽  
Amy E McGrath ◽  
Slobodan Jergic ◽  
John P McDonald ◽  
...  
Keyword(s):  
Dna Polymerase ◽  
Single Molecule ◽  
Strand Break ◽  
Double Strand Break ◽  
Double Strand Breaks ◽  
Strand Breaks ◽  
E Coli ◽  
Pol Iv ◽  
Dna Polymerase Iv

Abstract Several functions have been proposed for the Escherichia coli DNA polymerase IV (pol IV). Although much research has focused on a potential role for pol IV in assisting pol III replisomes in the bypass of lesions, pol IV is rarely found at the replication fork in vivo. Pol IV is expressed at increased levels in E. coli cells exposed to exogenous DNA damaging agents, including many commonly used antibiotics. Here we present live-cell single-molecule microscopy measurements indicating that double-strand breaks induced by antibiotics strongly stimulate pol IV activity. Exposure to the antibiotics ciprofloxacin and trimethoprim leads to the formation of double strand breaks in E. coli cells. RecA and pol IV foci increase after treatment and exhibit strong colocalization. The induction of the SOS response, the appearance of RecA foci, the appearance of pol IV foci and RecA-pol IV colocalization are all dependent on RecB function. The positioning of pol IV foci likely reflects a physical interaction with the RecA* nucleoprotein filaments that has been detected previously in vitro. Our observations provide an in vivo substantiation of a direct role for pol IV in double strand break repair in cells treated with double strand break-inducing antibiotics.

scholarly journals Repair of DNA Double-Strand Breaks following UV Damage in Three Sulfolobussolfataricus Strains

2010 ◽  
Vol 192 (19) ◽  
pp. 4954-4962 ◽  
Author(s):  
Michael L. Rolfsmeier ◽  
Marian F. Laughery ◽  
Cynthia A. Haseltine
Keyword(s):  
Sulfolobus Solfataricus ◽  
Strand Break ◽  
Double Strand Break ◽  
Double Strand Breaks ◽  
Double Strand Break Repair ◽  
Hyperthermophilic Archaea ◽  
Chromosomal Damage ◽  
Strand Breaks ◽  
Break Repair ◽  
Uv C

ABSTRACT DNA damage repair mechanisms have been most thoroughly explored in the eubacterial and eukaryotic branches of life. The methods by which members of the archaeal branch repair DNA are significantly less well understood but have been gaining increasing attention. In particular, the approaches employed by hyperthermophilic archaea have been a general source of interest, since these organisms thrive under conditions that likely lead to constant chromosomal damage. In this work we have characterized the responses of three Sulfolobus solfataricus strains to UV-C irradiation, which often results in double-strand break formation. We examined S. solfataricus strain P2 obtained from two different sources and S. solfataricus strain 98/2, a popular strain for site-directed mutation by homologous recombination. Cellular recovery, as determined by survival curves and the ability to return to growth after irradiation, was found to be strain specific and differed depending on the dose applied. Chromosomal damage was directly visualized using pulsed-field gel electrophoresis and demonstrated repair rate variations among the strains following UV-C irradiation-induced double-strand breaks. Several genes involved in double-strand break repair were found to be significantly upregulated after UV-C irradiation. Transcript abundance levels and temporal expression patterns for double-strand break repair genes were also distinct for each strain, indicating that these Sulfolobus solfataricus strains have differential responses to UV-C-induced DNA double-strand break damage.

scholarly journals YGR042W/MTE1 Functions in Double-Strand Break Repair with MPH1

2015 ◽  
Author(s):  
Askar Yimit ◽  
TaeHyung Kim ◽  
Ranjith Anand ◽  
Sarah Meister ◽  
Jiongwen Ou ◽  
...  
Keyword(s):  
Dna Damage ◽  
Strand Break ◽  
Double Strand Break ◽  
Dna Helicase ◽  
Double Strand Breaks ◽  
Double Strand Break Repair ◽  
Dependent Manner ◽  
Dna Breaks ◽  
Strand Breaks ◽  
Break Repair

Double-strand DNA breaks occur upon exposure of cells to agents such as ionizing radiation and ultraviolet light or indirectly through replication fork collapse at DNA damage sites. If left unrepaired double-strand breaks can cause genome instability and cell death. In response to DNA damage, proteins involved in double-strand break repair by homologous recombination re-localize into discrete nuclear foci. We identified 29 proteins that co-localize with the recombination repair protein Rad52 in response to DNA damage. Of particular interest, Ygr042w/Mte1, a protein of unknown function, showed robust colocalization with Rad52. Mte1 foci fail to form when the DNA helicase Mph1 is absent. Mte1 and Mph1 form a complex, and are recruited to double-strand breaks in vivo in a mutually dependent manner. Mte1 is important for resolution of Rad52 foci during double-strand break repair, and for suppressing break-induced replication. Together our data indicate that Mte1 functions with Mph1 in double-strand break repair.

scholarly journals In Vitro Repair of Gaps in Bacteriophage T7 DNA

1998 ◽  
Vol 180 (23) ◽  
pp. 6193-6202 ◽  
Author(s):  
Ying-Ta Lai ◽  
Warren Masker
Keyword(s):  
Strand Break ◽  
Double Strand Break ◽  
Double Strand Breaks ◽  
Double Strand Break Repair ◽  
Bacteriophage T7 ◽  
Dna Molecules ◽  
Strand Breaks ◽  
Highly Efficient ◽  
Break Repair

ABSTRACT An in vitro system based upon extracts of Escherichia coli infected with bacteriophage T7 was used to study the mechanism of double-strand break repair. Double-strand breaks were placed in T7 genomes by cutting with a restriction endonuclease which recognizes a unique site in the T7 genome. These molecules were allowed to repair under conditions where the double-strand break could be healed by (i) direct joining of the two partial genomes resulting from the break, (ii) annealing of complementary versions of 17-bp sequences repeated on either side of the break, or (iii) recombination with intact T7 DNA molecules. The data show that while direct joining and single-strand annealing contributed to repair of double-strand breaks, these mechanisms made only minor contributions. The efficiency of repair was greatly enhanced when DNA molecules that bridge the region of the double-strand break (referred to as donor DNA) were provided in the reaction mixtures. Moreover, in the presence of the donor DNA most of the repaired molecules acquired genetic markers from the donor DNA, implying that recombination between the DNA molecules was instrumental in repairing the break. Double-strand break repair in this system is highly efficient, with more than 50% of the broken molecules being repaired within 30 min under some experimental conditions. Gaps of 1,600 nucleotides were repaired nearly as well as simple double-strand breaks. Perfect homology between the DNA sequence near the break site and the donor DNA resulted in minor (twofold) improvement in the efficiency of repair. However, double-strand break repair was still highly efficient when there were inhomogeneities between the ends created by the double-strand break and the T7 genome or between the ends of the donor DNA molecules and the genome. The distance between the double-strand break and the ends of the donor DNA molecule was critical to the repair efficiency. The data argue that ends of DNA molecules formed by double-strand breaks are typically digested by between 150 and 500 nucleotides to form a gap that is subsequently repaired by recombination with other DNA molecules present in the same reaction mixture or infected cell.

scholarly journals PRDM9 losses in vertebrates are coupled to the loss of at least three other meiotic genes

2021 ◽  
Author(s):  
Maria Izabel Alves Cavassim ◽  
Zachary Baker ◽  
Carla Hoge ◽  
Mikkel Schierup ◽  
Molly Schumer ◽  
...  
Keyword(s):  
Candidate Genes ◽  
Phylogenetic Relationship ◽  
Strand Break ◽  
Double Strand Break ◽  
Double Strand Breaks ◽  
Double Strand Break Repair ◽  
Vertebrate Species ◽  
Strand Breaks ◽  
Domain Composition ◽  
Break Repair

In most mammals and likely throughout vertebrates, the gene PRDM9 specifies the locations of meiotic double strand breaks; in mice and humans at least, it also aids in their repair. For both roles, many of the molecular partners remain unknown. Here, we take a phylogenetic approach to identify genes that may be interacting with PRDM9, by leveraging the fact that PRDM9 arose before the origin of vertebrates, but was lost many times, either partially or entirely--and with it, its role in recombination. As a first step, we characterize PRDM9 domain composition across 379 vertebrate species, inferring at least eight independent losses. We then use the interdigitation of PRDM9 orthologs across vertebrates to test whether it co-evolved with any of 241 candidate genes co-expressed with PRDM9 in mice or associated with recombination phenotypes in mammals. Accounting for the phylogenetic relationship among species, we identify three genes whose presence and absence is unexpectedly coincident with that of PRDM9: ZCWPW1, which was recently shown to be recruited to sites of PRDM9 binding and to facilitate double strand break repair; TEX15, which has also been suggested to play a role in repair; and ZCWPW2, the paralog of ZCWPW1. ZCWPW2 is expected to be recruited to sites of PRDM9 binding as well; its tight coevolution with PRDM9 across vertebrates suggests that it is a key interactor, with a role either in recruiting the recombination machinery or in double strand break repair.

scholarly journals Phytotherapeutics oridonin and ponicidin show additive effects combined with irradiation in pancreatic cancer in vitro

2017 ◽  
Vol 51 (4) ◽  
pp. 407-414 ◽  
Author(s):  
Jakob Liermann ◽  
Patrick Naumann ◽  
Franco Fortunato ◽  
Thomas E. Schmid ◽  
Klaus-Josef Weber ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Strand Break ◽  
Double Strand Break ◽  
Double Strand Breaks ◽  
Double Strand Break Repair ◽  
Additive Effects ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Dna Double Strand Break

Abstract Background Chemoradiation of locally advanced non-metastatic pancreatic cancer can lead to secondary operability by tumor mass reduction. Here, we analyzed radiomodulating effects of oridonin and ponicidin in pancreatic cancer in vitro. Both agents are ent-kaurane diterpenoids, extracted from Isodon rubescens, a plant that is well known in Traditional Chinese Medicine. Cytotoxic effects have recently been shown in different tumor entities for both agents. Materials and methods Pancreatic cancer cell lines AsPC-1, BxPC-3, Panc-1 and MIA PaCa-2 were pretreated with oridonin or ponicidin and irradiated with 2 Gy to 6 Gy. Long-term survival was determined by clonogenic assay. Cell cycle effects and intensity of γH2AX as indicator for DNA double-strand breaks were investigated by flow cytometry. Western blotting was used to study the DNA double-strand break repair proteins Ku70, Ku80 and XRCC4. Results Oridonin and ponicidin lead to a dose-dependent reduction of clonogenic survival and an increase in γH2AX. Combined with irradiation we observed additive effects and a prolonged G2/M-arrest. No relevant changes in the levels of the DNA double-strand break repair proteins were detected. Conclusions Pretreatment with oridonin or ponicidin followed by irradiation lead to an additional reduction in survival of pancreatic cancer cells in vitro, presumably explained by an induced prolonged G2/M-arrest. Both agents seem to induce DNA double-strand breaks but do not interact with the non-homologous end joining (NHEJ) pathway.

Sign in / Sign up

Export Citation Format

Share Document