scholarly journals Recombinogenic Effects of DNA-Damaging Agents Are Synergistically Increased by Transcription inSaccharomyces cerevisiae: New Insights Into Transcription-Associated Recombination

Genetics ◽  
2003 ◽  
Vol 165 (2) ◽  
pp. 457-466 ◽  
Author(s):  
M García-Rubio ◽  
P Huertas ◽  
S González-Barrera ◽  
A Aguilera
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Dna Sequence ◽  
Direct Repeat ◽  
Methyl Methanesulfonate ◽  
Immunoglobulin Genes ◽  
Developmentally Regulated ◽  
Dna Damaging Agents ◽  
Regulated Promoters ◽  
Synergistic Increase

AbstractHomologous recombination of a particular DNA sequence is strongly stimulated by transcription, a phenomenon observed from bacteria to mammals, which we refer to as transcription-associated recombination (TAR). TAR might be an accidental feature of DNA chemistry with important consequences for genetic stability. However, it is also essential for developmentally regulated processes such as class switching of immunoglobulin genes. Consequently, it is likely that TAR embraces more than one mechanism. In this study we tested the possibility that transcription induces recombination by making DNA more susceptible to recombinogenic DNA damage. Using different plasmid-chromosome and direct-repeat recombination constructs in which transcription is driven from either the PGAL1- or the Ptet-regulated promoters, we haveshown that either 4-nitroquinoline-N-oxide (4-NQO) or methyl methanesulfonate (MMS) produces a synergistic increase of recombination when combined with transcription. 4-NQO and MMS stimulated recombination of a transcriptionally active DNA sequence up to 12,800- and 130-fold above the spontaneous levels observed in the absence of transcription, whereas 4-NQO and MMS alone increased recombination 193- and 4.5-fold, respectively. Our results provide evidence that TAR is due, at least in part, to the ability of transcription to enhance the accessibility of DNA to exogenous chemicals and internal metabolites responsible for recombinogenic lesions. We discuss possible parallelisms between the mechanisms of induction of recombination and mutation by transcription.

scholarly journals Mph1p promotes gross chromosomal rearrangement through partial inhibition of homologous recombination

2008 ◽  
Vol 181 (7) ◽  
pp. 1083-1093 ◽  
Author(s):  
Soma Banerjee ◽  
Stephanie Smith ◽  
Ji-Hyun Oum ◽  
Hung-Jiun Liaw ◽  
Ji-Young Hwang ◽  
...  
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Genomic Instability ◽  
Chromosomal Rearrangement ◽  
Protein A ◽  
Replication Protein A ◽  
Dna Helicase ◽  
Double Strand Breaks ◽  
Methyl Methanesulfonate ◽  
Strand Breaks

Gross chromosomal rearrangement (GCR) is a type of genomic instability associated with many cancers. In yeast, multiple pathways cooperate to suppress GCR. In a screen for genes that promote GCR, we identified MPH1, which encodes a 3′–5′ DNA helicase. Overexpression of Mph1p in yeast results in decreased efficiency of homologous recombination (HR) as well as delayed Rad51p recruitment to double-strand breaks (DSBs), which suggests that Mph1p promotes GCR by partially suppressing HR. A function for Mph1p in suppression of HR is further supported by the observation that deletion of both mph1 and srs2 synergistically sensitize cells to methyl methanesulfonate-induced DNA damage. The GCR-promoting activity of Mph1p appears to depend on its interaction with replication protein A (RPA). Consistent with this observation, excess Mph1p stabilizes RPA at DSBs. Furthermore, spontaneous RPA foci at DSBs are destabilized by the mph1Δ mutation. Therefore, Mph1p promotes GCR formation by partially suppressing HR, likely through its interaction with RPA.

scholarly journals Genetic Recombination in Bacillus subtilis 168: Effect of ΔhelD on DNA Repair and Homologous Recombination

2001 ◽  
Vol 183 (19) ◽  
pp. 5772-5777 ◽  
Author(s):  
Begoña Carrasco ◽  
Silvia Fernández ◽  
Marie-Agnes Petit ◽  
Juan C. Alonso
Keyword(s):  
Dna Repair ◽  
Bacillus Subtilis ◽  
Homologous Recombination ◽  
Genetic Recombination ◽  
Methyl Methanesulfonate ◽  
Plasmid Transformation ◽  
Dna Damaging Agents ◽  
Bacillus Subtilis 168 ◽  
Recombination Repair ◽  
Helicase Iv

ABSTRACT The B. subtilis ΔhelD allele rendered cells proficient in transformational recombination and moderately sensitive to methyl methanesulfonate when present in an otherwise Rec+ strain. The ΔhelD allele was introduced into rec-deficient strains representative of the α (recF strain), β (addA addB), γ (recH), ɛ (ΔrecU), and ζ (ΔrecS) epistatic groups. The ΔhelDmutation increased the sensitivity to DNA-damaging agents ofaddAB, ΔrecU, and ΔrecS cells, did not affect the survival ofrecH cells, and decreased the sensitivity ofrecF cells. ΔhelD also partially suppressed the DNA repair phenotype of other mutations classified within the α epistatic group, namely the recL, ΔrecO, and recR mutations. The ΔhelD allele marginally reduced plasmid transformation (three- to sevenfold) of mutations classified within the α, β, and γ epistatic groups. Altogether, these data indicate that the loss of helicase IV might stabilize recombination repair intermediates formed in the absence of recFLOR and renderrecFLOR, addAB, andrecH cells impaired in plasmid transformation.

scholarly journals DHX9-dependent recruitment of BRCA1 to RNA is required to promote DNA end resection in homologous recombination

2019 ◽  
Author(s):  
Prasun Chakraborty ◽  
Kevin Hiom
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Pivotal Role ◽  
Dna Breaks ◽  
Early Step ◽  
Dna And Rna ◽  
Dna Damaging Agents ◽  
Mediator Protein ◽  
Dna End Resection ◽  
End Resection

AbstractDExD/H-box helicase 9 (DHX9/RNA helicaseA) is ubiquitously expressed ATP-dependent helicase that unwinds a variety of complex DNA and RNA secondary structures, suggesting it might have a role in DNA replication and the repair of DNA damage. Here we identify a pivotal role for DHX9 in homologous recombination (HR). Cells that are deficient in DHX9 are impaired in the generation of single stranded DNA (ssDNA) by DNA end resection. Consequently these cells fail to recruit RPA and RAD51 to sites of DNA damage and are hypersensitive to treatment with the DNA damaging agents camptothecin and Olaparib. A critical early step in the initiation of HR is the recruitment of BRCA1 mediator protein to DNA damage to promote DNA resection. We show here that recruitment of BRCA1 to DNA damage foci is dependent on its interaction with DHX9 to form the BRCA1-D complex, which binds to nascent RNA. Together our data identify a pivotal role for DHX9 in homologous recombination and highlight the important contribution of RNA in the recruitment of BRCA1 to DNA damage for the repair of DNA breaks

scholarly journals Actin-Related Protein 6 (Arp6) Influences Double-Strand Break Repair in Yeast

2021 ◽  
Vol 1 (2) ◽  
pp. 225-238
Author(s):  
Mohsen Hooshyar ◽  
Daniel Burnside ◽  
Maryam Hajikarimlou ◽  
Katayoun Omidi ◽  
Alexander Jesso ◽  
...  
Keyword(s):  
Dna Damage ◽  
Chromatin Remodeling ◽  
Genetic Interaction ◽  
Interaction Analysis ◽  
Strand Break ◽  
Dna Double Strand Breaks ◽  
Dsb Repair ◽  
Dna Damaging Agents ◽  
Repair Efficiency ◽  
Chromosomal Breaks

DNA double-strand breaks (DSBs) are the most deleterious form of DNA damage and are repaired through non-homologous end-joining (NHEJ) or homologous recombination (HR). Repair initiation, regulation and communication with signaling pathways require several histone-modifying and chromatin-remodeling complexes. In budding yeast, this involves three primary complexes: INO80-C, which is primarily associated with HR, SWR1-C, which promotes NHEJ, and RSC-C, which is involved in both pathways as well as the general DNA damage response. Here we identify ARP6 as a factor involved in DSB repair through an RSC-C-related pathway. The loss of ARP6 significantly reduces the NHEJ repair efficiency of linearized plasmids with cohesive ends, impairs the repair of chromosomal breaks, and sensitizes cells to DNA-damaging agents. Genetic interaction analysis indicates that ARP6, MRE11 and RSC-C function within the same pathway, and the overexpression of ARP6 rescues rsc2∆ and mre11∆ sensitivity to DNA-damaging agents. Double mutants of ARP6, and members of the INO80 and SWR1 complexes, cause a significant reduction in repair efficiency, suggesting that ARP6 functions independently of SWR1-C and INO80-C. These findings support a novel role for ARP6 in DSB repair that is independent of the SWR1 chromatin remodeling complex, through an apparent RSC-C and MRE11-associated DNA repair pathway.

kangaroo, a Mobile Element From Volvox carteri, Is a Member of a Newly Recognized Third Class of Retrotransposons

Genetics ◽  
2002 ◽  
Vol 162 (4) ◽  
pp. 1617-1630
Author(s):  
Leonard Duncan ◽  
Kristine Bouckaert ◽  
Fay Yeh ◽  
David L Kirk
Keyword(s):  
Genomic Structure ◽  
Mobile Element ◽  
Direct Repeat ◽  
Structural Features ◽  
Volvox Carteri ◽  
Developmentally Regulated ◽  
Closed Circle ◽  
Integration Mechanisms ◽  
And Function

Abstract Retrotransposons play an important role in the evolution of genomic structure and function. Here we report on the characterization of a novel retrotransposon called kangaroo from the multicellular green alga, Volvox carteri. kangaroo elements are highly mobile and their expression is developmentally regulated. They probably integrate via double-stranded, closed-circle DNA intermediates through the action of an encoded recombinase related to the λ-site-specific integrase. Phylogenetic analysis indicates that kangaroo elements are closely related to other unorthodox retrotransposons including PAT (from a nematode), DIRS-1 (from Dictyostelium), and DrDIRS1 (from zebrafish). PAT and kangaroo both contain split direct repeat (SDR) termini, and here we show that DIRS-1 and DrDIRS1 elements contain terminal features structurally related to SDRs. Thus, these mobile elements appear to define a third class of retrotransposons (the DIRS1 group) that are unified by common structural features, genes, and integration mechanisms, all of which differ from those of LTR and conventional non-LTR retrotransposons.

scholarly journals Genotoxic and oxidative effect of duloxetine on mouse brain and liver tissues

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Isela Álvarez-González ◽  
Scarlett Camacho-Cantera ◽  
Patricia Gómez-González ◽  
Michael J. Rendón Barrón ◽  
José A. Morales-González ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Dna Damage ◽  
Mouse Brain ◽  
Control Level ◽  
Dna Oxidation ◽  
Methyl Methanesulfonate ◽  
Control Group ◽  
Oxidative Potential ◽  
The Brain ◽  
Oxidative Effect

AbstractWe evaluated the duloxetine DNA damaging capacity utilizing the comet assay applied to mouse brain and liver cells, as well as its DNA, lipid, protein, and nitric oxide oxidative potential in the same cells. A kinetic time/dose strategy showed the effect of 2, 20, and 200 mg/kg of the drug administered intraperitoneally once in comparison with a control and a methyl methanesulfonate group. Each parameter was evaluated at 3, 9, 15, and 21 h postadministration in five mice per group, except for the DNA oxidation that was examined only at 9 h postadministration. Results showed a significant DNA damage mainly at 9 h postexposure in both organs. In the brain, with 20 and 200 mg/kg we found 50 and 80% increase over the control group (p ≤ 0.05), in the liver, the increase of 2, 20, and 200 mg/kg of duloxetine was 50, 80, and 135% in comparison with the control level (p ≤ 0.05). DNA, lipid, protein and nitric oxide oxidation increase was also observed in both organs. Our data established the DNA damaging capacity of duloxetine even with a dose from the therapeutic range (2 mg/kg), and suggest that this effect can be related with its oxidative potential.

scholarly journals DHX9-dependent recruitment of BRCA1 to RNA promotes DNA end resection in homologous recombination

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Prasun Chakraborty ◽  
Kevin Hiom
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Rna Polymerase Ii ◽  
Critical Role ◽  
Dna Breaks ◽  
Double Stranded Dna ◽  
Recombination Repair ◽  
Dna End Resection ◽  
End Resection ◽  
Rna Polymerase Ii Transcription

AbstractDouble stranded DNA Breaks (DSB) that occur in highly transcribed regions of the genome are preferentially repaired by homologous recombination repair (HR). However, the mechanisms that link transcription with HR are unknown. Here we identify a critical role for DHX9, a RNA helicase involved in the processing of pre-mRNA during transcription, in the initiation of HR. Cells that are deficient in DHX9 are impaired in the recruitment of RPA and RAD51 to sites of DNA damage and fail to repair DSB by HR. Consequently, these cells are hypersensitive to treatment with agents such as camptothecin and Olaparib that block transcription and generate DSB that specifically require HR for their repair. We show that DHX9 plays a critical role in HR by promoting the recruitment of BRCA1 to RNA as part of the RNA Polymerase II transcription complex, where it facilitates the resection of DSB. Moreover, defects in DHX9 also lead to impaired ATR-mediated damage signalling and an inability to restart DNA replication at camptothecin-induced DSB. Together, our data reveal a previously unknown role for DHX9 in the DNA Damage Response that provides a critical link between RNA, RNA Pol II and the repair of DNA damage by homologous recombination.

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