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de Moraes MH, Hsu F, Huang D, Bosch DE, Zeng J, Radey MC, Simon N, Ledvina HE, Frick JP, Wiggins PA, Peterson SB, Mougous JD. An interbacterial DNA deaminase toxin directly mutagenizes surviving target populations. eLife 2021; 10:62967. [PMID: 33448264 PMCID: PMC7901873 DOI: 10.7554/elife.62967] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 01/14/2021] [Indexed: 12/12/2022] Open
Abstract
When bacterial cells come in contact, antagonism mediated by the delivery of toxins frequently ensues. The potential for such encounters to have long-term beneficial consequences in recipient cells has not been investigated. Here, we examined the effects of intoxication by DddA, a cytosine deaminase delivered via the type VI secretion system (T6SS) of Burkholderia cenocepacia. Despite its killing potential, we observed that several bacterial species resist DddA and instead accumulate mutations. These mutations can lead to the acquisition of antibiotic resistance, indicating that even in the absence of killing, interbacterial antagonism can have profound consequences on target populations. Investigation of additional toxins from the deaminase superfamily revealed that mutagenic activity is a common feature of these proteins, including a representative we show targets single-stranded DNA and displays a markedly divergent structure. Our findings suggest that a surprising consequence of antagonistic interactions between bacteria could be the promotion of adaptation via the action of directly mutagenic toxins.
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Affiliation(s)
- Marcos H de Moraes
- Department of Microbiology, University of Washington School of Medicine, Seattle, United States
| | - FoSheng Hsu
- Department of Microbiology, University of Washington School of Medicine, Seattle, United States
| | - Dean Huang
- Department of Physics, University of Washington, Seattle, United States
| | - Dustin E Bosch
- Department of Laboratory Medicine and Pathology, University of Washington School of Medicine, Seattle, United States
| | - Jun Zeng
- Department of Microbiology, University of Washington School of Medicine, Seattle, United States
| | - Matthew C Radey
- Department of Microbiology, University of Washington School of Medicine, Seattle, United States
| | - Noah Simon
- Department of Biostatistics, University of Washington School of Public Health, Seattle, United States
| | - Hannah E Ledvina
- Department of Microbiology, University of Washington School of Medicine, Seattle, United States
| | - Jacob P Frick
- Department of Microbiology, University of Washington School of Medicine, Seattle, United States
| | - Paul A Wiggins
- Department of Physics, University of Washington, Seattle, United States
| | - S Brook Peterson
- Department of Microbiology, University of Washington School of Medicine, Seattle, United States
| | - Joseph D Mougous
- Department of Microbiology, University of Washington School of Medicine, Seattle, United States.,Department of Biochemistry, University of Washington School of Medicine, Seattle, United States.,Howard Hughes Medical Institute, University of Washington, Seattle, United States
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2
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Thapa SS, Grove A. Impaired purine homeostasis plays a primary role in trimethoprim-mediated induction of virulence genes in Burkholderia thailandensis. Mol Microbiol 2020; 115:610-622. [PMID: 33053234 DOI: 10.1111/mmi.14626] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 10/08/2020] [Accepted: 10/09/2020] [Indexed: 11/27/2022]
Abstract
One of the most commonly prescribed antibiotics against Burkholderia infections is co-trimoxazole, a cocktail of trimethoprim and sulfamethoxazole. Trimethoprim elicits an upregulation of the mal gene cluster, which encodes proteins involved in synthesis of the cytotoxic polyketide malleilactone; trimethoprim does so by increasing expression of the malR gene, which encodes the activator MalR. We report that B. thailandensis grown on trimethoprim exhibited increased virulence against Caenorhabditis elegans. This enhanced virulence correlated with an increase in expression of the mal gene cluster. Notably, inhibition of xanthine dehydrogenase by addition of allopurinol led to similar upregulation of malA and malR, with addition of trimethoprim or allopurinol also resulting in an equivalent intracellular accumulation of xanthine. Xanthine is a ligand for the transcription factor MftR that leads to attenuated DNA binding, and we show using chromatin immunoprecipitation that MftR binds directly to malR. Our gene expression data suggest that malR expression is repressed by both MftR and by a separate transcription factor, which also responds to a metabolite that accumulates on exposure to trimethoprim. Since allopurinol elicits a similar increase in malR/malA expression as trimethoprim, we suggest that impaired purine homeostasis plays a primary role in trimethoprim-mediated induction of malR and in turn malA.
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Affiliation(s)
- Sudarshan S Thapa
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA
| | - Anne Grove
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA
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3
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Fluoropyrimidine Modulation of the Anti-Tumor Immune Response-Prospects for Improved Colorectal Cancer Treatment. Cancers (Basel) 2020; 12:cancers12061641. [PMID: 32575843 PMCID: PMC7352193 DOI: 10.3390/cancers12061641] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 06/18/2020] [Accepted: 06/19/2020] [Indexed: 02/07/2023] Open
Abstract
Chemotherapy modulates the anti-tumor immune response and outcomes depend on the balance of favorable and unfavorable effects of drugs on anti-tumor immunity. 5-Florouracil (5-FU) is widely used in adjuvant chemotherapy regimens to treat colorectal cancer (CRC) and provides a survival benefit. However, survival remains poor for CRC patients with advanced and metastatic disease and immune checkpoint blockade therapy benefits only a sub-set of CRC patients. Here we discuss the effects of 5-FU-based chemotherapy regimens to the anti-tumor immune response. We consider how different aspects of 5-FU's multi-factorial mechanism differentially affect malignant and immune cell populations. We summarize recent studies with polymeric fluoropyrimidines (e.g., F10, CF10) that enhance DNA-directed effects and discuss how such approaches may be used to enhance the anti-tumor immune response and improve outcomes.
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4
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Replication Rapidly Recovers and Continues in the Presence of Hydroxyurea in Escherichia coli. J Bacteriol 2018; 200:JB.00713-17. [PMID: 29263100 DOI: 10.1128/jb.00713-17] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2017] [Accepted: 12/14/2017] [Indexed: 12/15/2022] Open
Abstract
In both prokaryotes and eukaryotes, hydroxyurea is suggested to inhibit DNA replication by inactivating ribonucleotide reductase and depleting deoxyribonucleoside triphosphate pools. In this study, we show that the inhibition of replication in Escherichia coli is transient even at concentrations of 0.1 M hydroxyurea and that replication rapidly recovers and continues in its presence. The recovery of replication does not require the alternative ribonucleotide reductases NrdEF and NrdDG or the translesion DNA polymerases II (Pol II), Pol IV, and Pol V. Ribonucleotides are incorporated at higher frequencies during replication in the presence of hydroxyurea. However, they do not contribute significantly to the observed synthesis or toxicity. Hydroxyurea toxicity was observed only under conditions where the stability of hydroxyurea was compromised and by-products known to damage DNA directly were allowed to accumulate. The results demonstrate that hydroxyurea is not a direct or specific inhibitor of DNA synthesis in vivo and that the transient inhibition observed is most likely due to a general depletion of iron cofactors from enzymes when 0.1 M hydroxyurea is initially applied. Finally, the results support previous studies suggesting that hydroxyurea toxicity is mediated primarily through direct DNA damage induced by the breakdown products of hydroxyurea, rather than by inhibition of replication or depletion of deoxyribonucleotide levels in the cell.IMPORTANCE Hydroxyurea is commonly suggested to function by inhibiting DNA replication through the inactivation of ribonucleotide reductase and depleting deoxyribonucleoside triphosphate pools. Here, we show that hydroxyurea only transiently inhibits replication in Escherichia coli before replication rapidly recovers and continues in the presence of the drug. The recovery of replication does not depend on alternative ribonucleotide reductases, translesion synthesis, or RecA. Further, we show that hydroxyurea toxicity is observed only in the presence of toxic intermediates that accumulate when hydroxyurea breaks down, damage DNA, and induce lethality. The results demonstrate that hydroxyurea toxicity is mediated indirectly by the formation of DNA damage, rather than by inhibition of replication or depletion of deoxyribonucleotide levels in the cell.
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Charbon G, Riber L, Løbner-Olesen A. Countermeasures to survive excessive chromosome replication in Escherichia coli. Curr Genet 2017; 64:71-79. [PMID: 28664289 DOI: 10.1007/s00294-017-0725-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 06/20/2017] [Accepted: 06/22/2017] [Indexed: 02/05/2023]
Abstract
In Escherichia coli, like all organisms, DNA replication is coordinated with cell cycle progression to ensure duplication of the genome prior to cell division. Chromosome replication is initiated from the replication origin, oriC, by the DnaA protein associated with ATP. Initiations take place once per cell cycle and in synchrony at all cellular origins. DnaA also binds ADP with similar affinity as ATP and in wild-type cells the majority of DnaA molecules are ADP bound. In cells where the DnaAATP/DnaAADP ratio increases or in cells where DnaAATP has increased access to oriC, premature initiations take place, often referred to as overinitiation. Overinitiating cells are generally characterized by their slow growth and in the most severe cases lethal accumulation of DNA strand breaks. Here, we review the different strategies adopted by E. coli to survive overinitiation. We propose a unifying model where all mutations that suppress overinitiation keep replication forks separated in time and, thereby, reduce the formation of strand breaks. One group of mutations does so by lowering the activity of oriC and/or DnaA to reduce the frequency of initiations to an acceptable level. In the other group of mutations, replication forks are kept apart by preventing formation of damages that would otherwise cause replication blocks, by allowing bypass of replication blocks and/or by slowing down replication forks. This group of suppressors restores viability despite excessive chromosome replication and provides new insights into mechanisms that safeguard DNA integrity.
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Affiliation(s)
- Godefroid Charbon
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, 2200, Copenhagen N, Denmark.
| | - Leise Riber
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, 2200, Copenhagen N, Denmark
| | - Anders Løbner-Olesen
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, 2200, Copenhagen N, Denmark.
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Abstract
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Phenotypic memory can predispose
cells to physiological outcomes,
contribute to heterogeneity in cellular populations, and allow computation
of environmental features, such as nutrient gradients. In bacteria
and synthetic circuits in general, memory can often be set by protein
concentrations: because of the relative stability of proteins, the
degradation rate is often dominated by the growth rate, and inheritance
is a significant factor. Cells can then be primed to respond to events
that recur with frequencies faster than the time to eliminate proteins.
Protein memory can be extended if cells reach extremely low growth
rates or no growth. Here we characterize the necessary time scales
for different quantities of protein memory, measured as relative entropy
(Kullback–Leibler divergence), for a variety of cellular growth
arrest transition dynamics. We identify a critical manifold in relative
protein degradation/growth arrest time scales where information is,
in principle, preserved indefinitely because proteins are trapped
at a concentration determined by the competing time scales as long
as nongrowth-mediated protein degradation is negligible. We next asked
what characteristics of growth arrest dynamics and initial protein
distributions best preserve or eliminate information about previous
environments. We identified that sharp growth arrest transitions with
skewed initial protein distributions optimize flexibility, with information
preservation and minimal cost of residual protein. As a result, a
nearly memoryless regime, corresponding to a form of bet-hedging,
may be an optimal strategy for storage of information by protein concentrations
in growth-arrested cells.
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Affiliation(s)
- J. Christian J. Ray
- Center for Computational
Biology Department of Molecular Biosciences, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047, United States
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7
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Gmeiner WH, Debinski W, Milligan C, Caudell D, Pardee TS. The applications of the novel polymeric fluoropyrimidine F10 in cancer treatment: current evidence. Future Oncol 2016; 12:2009-20. [PMID: 27279153 DOI: 10.2217/fon-2016-0091] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
F10 is a novel polymeric fluoropyrimidine drug candidate with strong anticancer activity in multiple preclinical models. F10 has strong potential for impacting cancer treatment because it displays high cytotoxicity toward proliferating malignant cells with minimal systemic toxicities thus providing an improved therapeutic window relative to traditional fluoropyrimidine drugs, such as 5-fluorouracil. F10 has a unique mechanism that involves dual targeting of thymidylate synthase and Top1. In this review, the authors provide an overview of the studies that revealed the novel aspects of F10's cytotoxic mechanism and summarize results obtained in preclinical models of acute myeloid leukemia, acute lymphocytic leukemia, glioblastoma and prostate cancer that demonstrate the strong potential of F10 to improve treatment outcomes.
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Affiliation(s)
- William H Gmeiner
- Wake Forest Baptist Medical Center Comprehensive Cancer Center, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA.,Department of Cancer Biology, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA
| | - Waldemar Debinski
- Wake Forest Baptist Medical Center Comprehensive Cancer Center, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA.,Department of Cancer Biology, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA.,Department of Radiation Oncology, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA
| | - Carol Milligan
- Wake Forest Baptist Medical Center Comprehensive Cancer Center, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA.,Department of Neurobiology & Anatomy, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA
| | - David Caudell
- Wake Forest Baptist Medical Center Comprehensive Cancer Center, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA.,Department of Pathology, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA
| | - Timothy S Pardee
- Wake Forest Baptist Medical Center Comprehensive Cancer Center, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA.,Department of Cancer Biology, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA.,Department of Hematology/Oncology, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA
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8
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A DinB Ortholog Enables Mycobacterial Growth under dTTP-Limiting Conditions Induced by the Expression of a Mycobacteriophage-Derived Ribonucleotide Reductase Gene. J Bacteriol 2015; 198:352-62. [PMID: 26527643 DOI: 10.1128/jb.00669-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 10/24/2015] [Indexed: 01/30/2023] Open
Abstract
UNLABELLED Mycobacterium species such as M. smegmatis and M. tuberculosis encode at least two translesion synthesis (TLS) polymerases, DinB1 and DinB2, respectively. Although predicted to be linked to DNA repair, their role in vivo remains enigmatic. M. smegmatis mc(2)155, a strain commonly used to investigate mycobacterial genetics, has two copies of dinB2, the gene that codes for DinB2, by virtue of a 56-kb chromosomal duplication. Expression of a mycobacteriophage D29 gene (gene 50) encoding a class II ribonucleotide reductase in M. smegmatis ΔDRKIN, a strain derived from mc(2)155 in which one copy of the duplication is lost, resulted in DNA replication defects and growth inhibition. The inhibitory effect could be linked to the deficiency of dTTP that resulted under these circumstances. The selective inhibition observed in the ΔDRKIN strain was found to be due solely to a reduced dosage of dinB2 in this strain. Mycobacterium bovis, which is closely related to M. tuberculosis, the tuberculosis pathogen, was found to be highly susceptible to gene 50 overexpression. Incidentally, these slow-growing pathogens harbor one copy of dinB2. The results indicate that the induction of a dTTP-limiting state can lead to growth inhibition in mycobacteria, with the effect being maximum in cells deficient in DinB2. IMPORTANCE Mycobacterium species, such as M. tuberculosis, the tuberculosis pathogen, are known to encode several Y family DNA polymerases, one of which is DinB2, an ortholog of the DNA repair-related protein DinP of Escherichia coli. Although this protein has been biochemically characterized previously and found to be capable of translesion synthesis in vitro, its in vivo function remains unknown. Using a novel method to induce dTTP deficiency in mycobacteria, we demonstrate that DinB2 can aid mycobacterial survival under such conditions. Apart from unraveling a specific role for the mycobacterial Y family DNA polymerase DinB2 for the first time, this study also paves the way for the development of drugs that can kill mycobacteria by inducing a dTTP-deficient state.
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Khodursky A, Guzmán EC, Hanawalt PC. Thymineless Death Lives On: New Insights into a Classic Phenomenon. Annu Rev Microbiol 2015; 69:247-63. [PMID: 26253395 DOI: 10.1146/annurev-micro-092412-155749] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The primary mechanisms by which bacteria lose viability when deprived of thymine have been elusive for over half a century. Early research focused on stalled replication forks and the deleterious effects of uracil incorporation into DNA from thymidine-deficient nucleotide pools. The initiation of the replication cycle and origin-proximal DNA degradation during thymine starvation have now been quantified via whole-genome microarrays and other approaches. These advances have fostered innovative models and informative experiments in bacteria since this topic was last reviewed. Given that thymineless death is similar in mammalian cells and that certain antibacterial and chemotherapeutic drugs elicit thymine deficiency, a mechanistic understanding of this phenomenon might have valuable biomedical applications.
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Affiliation(s)
- Arkady Khodursky
- Biotechnology Institute and Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, Minnesota 55108;
| | - Elena C Guzmán
- Departamento de Bioquímica Biología Molecular y Genética, Universidad de Extremadura, 06071 Badajoz, Spain;
| | - Philip C Hanawalt
- Department of Biology, Stanford University, Stanford, California 94305;
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Zaritsky A, Woldringh CL. Chromosome replication, cell growth, division and shape: a personal perspective. Front Microbiol 2015; 6:756. [PMID: 26284044 PMCID: PMC4522554 DOI: 10.3389/fmicb.2015.00756] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 07/10/2015] [Indexed: 11/13/2022] Open
Abstract
The origins of Molecular Biology and Bacterial Physiology are reviewed, from our personal standpoints, emphasizing the coupling between bacterial growth, chromosome replication and cell division, dimensions and shape. Current knowledge is discussed with historical perspective, summarizing past and present achievements and enlightening ideas for future studies. An interactive simulation program of the bacterial cell division cycle (BCD), described as "The Central Dogma in Bacteriology," is briefly represented. The coupled process of transcription/translation of genes encoding membrane proteins and insertion into the membrane (so-called transertion) is invoked as the functional relationship between the only two unique macromolecules in the cell, DNA and peptidoglycan embodying the nucleoid and the sacculus respectively. We envision that the total amount of DNA associated with the replication terminus, so called "nucleoid complexity," is directly related to cell size and shape through the transertion process. Accordingly, the primary signal for cell division transmitted by DNA dynamics (replication, transcription and segregation) to the peptidoglycan biosynthetic machinery is of a physico-chemical nature, e.g., stress in the plasma membrane, relieving nucleoid occlusion in the cell's center hence enabling the divisome to assemble and function between segregated daughter nucleoids.
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Affiliation(s)
- Arieh Zaritsky
- Faculty of Natural Sciences, Ben-Gurion University of the Negev, Be’er-Sheva, Israel
| | - Conrad L. Woldringh
- Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, Netherlands
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