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North H, McLaughlin M, Fiebig A, Crosson S. The Caulobacter NtrB-NtrC two-component system bridges nitrogen assimilation and cell development. J Bacteriol 2023; 205:e0018123. [PMID: 37791753 PMCID: PMC10601693 DOI: 10.1128/jb.00181-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 09/03/2023] [Indexed: 10/05/2023] Open
Abstract
A suite of molecular sensory systems enables Caulobacter to control growth, development, and reproduction in response to levels of essential elements. The bacterial enhancer-binding protein (bEBP) NtrC and its cognate sensor histidine kinase, NtrB, are key regulators of nitrogen assimilation in many bacteria, but their roles in Caulobacter metabolism and development are not well defined. Notably, Caulobacter NtrC is an unconventional bEBP that lacks the σ54-interacting loop commonly known as the GAFTGA motif. Here we show that deletion of Caulobacter crescentus ntrC slows cell growth in complex medium and that ntrB and ntrC are essential when ammonium is the sole nitrogen source due to their requirement for glutamine synthetase expression. Random transposition of a conserved IS3-family mobile genetic element frequently rescued the growth defect of ntrC mutant strains by restoring transcription of the glnBA operon, revealing a possible role for IS3 transposition in shaping the evolution of Caulobacter populations during nutrient limitation. We further identified dozens of direct NtrC-binding sites on the C. crescentus chromosome, with a large fraction located near genes involved in polysaccharide biosynthesis. The majority of binding sites align with those of the essential nucleoid-associated protein, GapR, or the cell cycle regulator, MucR1. NtrC is therefore predicted to directly impact the regulation of cell cycle and cell development. Indeed, loss of NtrC function led to elongated polar stalks and elevated synthesis of cell envelope polysaccharides. This study establishes regulatory connections between NtrC, nitrogen metabolism, polar morphogenesis, and envelope polysaccharide synthesis in Caulobacter. IMPORTANCE Bacteria balance cellular processes with the availability of nutrients in their environment. The NtrB-NtrC two-component signaling system is responsible for controlling nitrogen assimilation in many bacteria. We have characterized the effect of ntrB and ntrC deletion on Caulobacter growth and development and uncovered a role for spontaneous IS element transposition in the rescue of transcriptional and nutritional deficiencies caused by ntrC mutation. We further defined the regulon of Caulobacter NtrC, a bacterial enhancer-binding protein, and demonstrate that it shares specific binding sites with essential proteins involved in cell cycle regulation and chromosome organization. Our work provides a comprehensive view of transcriptional regulation mediated by a distinctive NtrC protein, establishing its connection to nitrogen assimilation and developmental processes in Caulobacter.
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Affiliation(s)
- Hunter North
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Maeve McLaughlin
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Aretha Fiebig
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Sean Crosson
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
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North H, McLaughlin M, Fiebig A, Crosson S. The Caulobacter NtrB-NtrC two-component system bridges nitrogen assimilation and cell development. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.06.543975. [PMID: 37333394 PMCID: PMC10274813 DOI: 10.1101/2023.06.06.543975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
A suite of molecular sensory systems enables Caulobacter to control growth, development, and reproduction in response to levels of essential elements. The bacterial enhancer binding protein (bEBP) NtrC, and its cognate sensor histidine kinase NtrB, are key regulators of nitrogen assimilation in many bacteria, but their roles in Caulobacter metabolism and development are not well defined. Notably, Caulobacter NtrC is an unconventional bEBP that lacks the σ54-interacting loop commonly known as the GAFTGA motif. Here we show that deletion of C. crescentus ntrC slows cell growth in complex medium, and that ntrB and ntrC are essential when ammonium is the sole nitrogen source due to their requirement for glutamine synthetase (glnA) expression. Random transposition of a conserved IS3-family mobile genetic element frequently rescued the growth defect of ntrC mutant strains by restoring transcription of the glnBA operon, revealing a possible role for IS3 transposition in shaping the evolution of Caulobacter populations during nutrient limitation. We further identified dozens of direct NtrC binding sites on the C. crescentus chromosome, with a large fraction located near genes involved in polysaccharide biosynthesis. The majority of binding sites align with those of the essential nucleoid associated protein, GapR, or the cell cycle regulator, MucR1. NtrC is therefore predicted to directly impact the regulation of cell cycle and cell development. Indeed, loss of NtrC function led to elongated polar stalks and elevated synthesis of cell envelope polysaccharides. This study establishes regulatory connections between NtrC, nitrogen metabolism, polar morphogenesis, and envelope polysaccharide synthesis in Caulobacter .
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Affiliation(s)
- Hunter North
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan USA
| | - Maeve McLaughlin
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan USA
| | - Aretha Fiebig
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan USA
| | - Sean Crosson
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan USA
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3
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Sundaram K, Vajravelu LK, Paul AJ. Functional characterization of toxin-antitoxin system in Mycobacterium tuberculosis. Indian J Tuberc 2023; 70:149-157. [PMID: 37100570 DOI: 10.1016/j.ijtb.2022.05.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 05/06/2022] [Accepted: 05/20/2022] [Indexed: 04/28/2023]
Abstract
Toxin-Antitoxin (TA) system is abundant in the microbial genome, especially in bacteria and archaea. Its genetic elements and addiction modules with the role of bacterial persistence and virulence. The TA system consists of a toxin and most unstable antitoxin that could be a protein or non-encoded RNA, TA loci are chromosomally determined and their cellular functions are mostly unknown. Approximately 93 TA systems were demonstrated and more functionally available in M. tuberculosis (Mtb), the organism responsible for tuberculosis (TB). It is an airborne disease, which is causing ill-health to humans. M. tuberculosis possesses higher TA loci than other microbes and non-tubercle bacilli, the following TA types have been identified such as VapBC, MazEF, HigBA, RelBE, ParDE, DarTG, PemIK, MbcTA, and one tripartite type II TAC-Chaperone system. Toxin-antitoxin Database (TADB) brings a detailed update on Toxin-Antitoxin classification in the different pathogens such as staphylococcus aureus, streptococcus pneumonia, Vibrio cholerae, Salmonella typhimurium, Shigella flexneri, and helicobacter pylori, etc. So, this Toxin-Antitoxin system is a master regulator for bacterial growth, and an essential factor in analyzing the properties and function of disease persistence, biofilm formation, and pathogenicity. The TA system is an advanced tool to develop a new therapeutic agent against M. tuberculosis.
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Affiliation(s)
- Karthikeyan Sundaram
- Department of Microbiology, SRM Medical College Hospital and Research Centre, Kattangulathur, Chennai, 603203, Tamilnadu, India.
| | - Leela Kagithakara Vajravelu
- Department of Microbiology, SRM Medical College Hospital and Research Centre, Kattangulathur, Chennai, 603203, Tamilnadu, India
| | - Alamu Juliana Paul
- Department of Microbiology, SRM Medical College Hospital and Research Centre, Kattangulathur, Chennai, 603203, Tamilnadu, India
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Liu H, Su L, Zhu T, Zhu X, Zhu Y, Peng Y, Zhang K, Wang L, Hu C, Chen H, Chen Y, Guo A. Comparative Analysis on Proteomics Profiles of Intracellular and Extracellular M.tb and BCG From Infected Human Macrophages. Front Genet 2022; 13:847838. [PMID: 35419023 PMCID: PMC8995892 DOI: 10.3389/fgene.2022.847838] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Accepted: 02/08/2022] [Indexed: 11/22/2022] Open
Abstract
Tuberculosis is the second cause in infectious diseases leading to human death. Understanding the virulence mechanism is inevitable if the disease needs to be fully cured. Therefore, this study aimed to reveal this mechanism by comparing proteomic profiles of intracellular and extracellular virulent strain M.tb and bacille Calmette–Guérin (BCG) from infected THP-1cells. First, M.tb and BCG infected THP-1 at MOI 10:1. Twelve hours postinfection, intracellular bacteria of M.tb and BCG were collected, whereas the two bacilli cultured in 7H9 broth media were used as the control. Then four groups of bacilli were subjected to proteomic analysis, and differential proteomic profiles between M.tb and BCG were comparatively analyzed with bioinformatics tools. As a result, we identified a total of 1,557 proteins. Further, they were divided into four groups for comparison of M.tb versus BCG under 7H9 culture (shorten as out), M.tb in (intracellular) versus M.tb out, BCG in versus BCG out and M.tb in versus BCG in. Between M.tb in versus BCG in, a total of 211 differentially expressed proteins were found. Eight proteins like ESAT-6 distributed in six RDs and some known proteins related to virulence. Besides, five uncharacterized proteins were differentially expressed. Further analysis revealed enriched pathways were associated with glyoxylate and dicarboxylate metabolism pathways. In M.tb out versus BCG out, a total of 144 differential proteins were identified and mainly involved in metabolism pathways. Then, 121 differential proteins in the group of M.tb in versus M.tb out were enriched in ribosome and oxidative phosphorylation related to adaptation to the host environment. The group of BCG in versus BCG out shared the same trend of different pathways to the M.tb in versus M.tb out. Finally, 42 proteins were identified to be up-regulated only in intracellular M.tb including eight RD proteins, whereas 22 up-regulated uniquely in intracellular BCG. Besides, only two proteins (Pks13 and Rv1405c) were commonly up-regulated in intracellular M.tb and BCG. Further, some unknown proteins were uniquely up-regulated in the intracellular M.tb and BCG. These findings provide valuable data for further exploration of molecular mechanism for M.tb virulence and BCG immune response.
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Affiliation(s)
- Han Liu
- The State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China.,College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Li Su
- The State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China.,College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Tingting Zhu
- The State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China.,College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Xiaojie Zhu
- The State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China.,College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Yifan Zhu
- The State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China.,College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Yonchong Peng
- The State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China.,College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Kailun Zhang
- The State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China.,College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Longwei Wang
- College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Changmin Hu
- College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,National Animal Tuberculosis Para-Reference Laboratory (Wuhan) of Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China
| | - Huanchun Chen
- The State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China.,College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,National Animal Tuberculosis Para-Reference Laboratory (Wuhan) of Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China
| | - Yingyu Chen
- The State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China.,College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,National Animal Tuberculosis Para-Reference Laboratory (Wuhan) of Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China
| | - Aizhen Guo
- The State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China.,College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,National Animal Tuberculosis Para-Reference Laboratory (Wuhan) of Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China.,Hubei International Scientific and Technological Cooperation Base of Veterinary Epidemiology, Huazhong Agricultural University, Wuhan, China
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Andrews ESV, Patrick WM. The hypothesized role of YbeZ in 16S rRNA maturation. Arch Microbiol 2022; 204:114. [PMID: 34984547 DOI: 10.1007/s00203-021-02739-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 12/20/2021] [Accepted: 12/21/2021] [Indexed: 11/28/2022]
Abstract
Ribosomes are the protein production machines in all living cells. Yet in contrast to our understanding of how the ribosome translates DNA information into life, the steps involved in ribosome biogenesis, the assembly of the ribosomal RNA (rRNA) and protein molecules that make up the ribosome, remain incomplete. YbeY is considered one of the most physiologically critical endoribonucleases and is implicated in numerous roles involving RNA including 16S rRNA maturation, yet our existing knowledge of its biochemical function fails to explain the phenotypes that manifest when it is lost. In bacteria, it is common for functionally associated genes to be found co-localized in the genome. Across phylogenetically diverse bacteria, the gene encoding ybeZ, encoding a PhoH domain protein, sits adjacent to ybeY. Recent experimental evidence has shown that PhoH domains are RNA helicases, suggesting that this is also the role of YbeZ. The role of an RNA helicase to support the function of YbeY would help explain its reported biochemistry; therefore, we propose a model for the function of YbeZ in 16S rRNA maturation, linking it with the most recent hypotheses on the function of YbeY, that YbeY together with other ribosomal proteins, and ribosome-associated proteins, plays a role in the biogenesis of the small ribosomal subunit. Our model provides a testable hypothesis to resolve the outstanding details surrounding ribosome biogenesis in bacteria.
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Affiliation(s)
- Emma S V Andrews
- Centre for Biodiscovery, School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand.
| | - Wayne M Patrick
- Centre for Biodiscovery, School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
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Rain-Franco A, Mouquet N, Gougat-Barbera C, Bouvier T, Beier S. Niche breadth affects bacterial transcription patterns along a salinity gradient. Mol Ecol 2021; 31:1216-1233. [PMID: 34878694 DOI: 10.1111/mec.16316] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 11/04/2021] [Accepted: 11/12/2021] [Indexed: 11/29/2022]
Abstract
Understanding the molecular mechanisms that determine a species' life history is important for predicting their susceptibility to environmental change. While specialist species with a narrow niche breadth (NB) maximize their fitness in their optimum habitat, generalists with broad NB adapt to multiple environments. The main objective of this study was to identify general transcriptional patterns that would distinguish bacterial strains characterized by contrasted NBs along a salinity gradient. More specifically, we hypothesized that genes encoding fitness-related traits, such as biomass production, have a higher degree of transcriptional regulation in specialists than in generalists, because the fitness of specialists is more variable under environmental change. By contrast, we expected that generalists would exhibit enhanced transcriptional regulation of genes encoding traits that protect them against cellular damage. To test these hypotheses, we assessed the transcriptional regulation of fitness-related and adaptation-related genes of 11 bacterial strains in relation to their NB and stress exposure under changing salinity conditions. The results suggested that transcriptional regulation levels of fitness- and adaptation-related genes correlated with the NB and/or the stress exposure of the inspected strains. We further identified a shortlist of candidate stress marker genes that could be used in future studies to monitor the susceptibility of bacterial populations or communities to environmental changes.
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Affiliation(s)
- Angel Rain-Franco
- CNRS, Laboratoire d'Océanographie Microbienne, LOMIC, Sorbonne Université, Banyuls/mer, France
| | - Nicolas Mouquet
- MARBEC, CNRS, Ifremer, IRD, Université de Montpellier, Montpellier, France
| | | | - Thierry Bouvier
- MARBEC, CNRS, Ifremer, IRD, Université de Montpellier, Montpellier, France
| | - Sara Beier
- CNRS, Laboratoire d'Océanographie Microbienne, LOMIC, Sorbonne Université, Banyuls/mer, France.,Leibniz Institute for Baltic Sea Research, Warnemünde, Germany
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M. Iyer L, Anantharaman V, Krishnan A, Burroughs AM, Aravind L. Jumbo Phages: A Comparative Genomic Overview of Core Functions and Adaptions for Biological Conflicts. Viruses 2021; 13:v13010063. [PMID: 33466489 PMCID: PMC7824862 DOI: 10.3390/v13010063] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 12/31/2020] [Accepted: 12/31/2020] [Indexed: 02/07/2023] Open
Abstract
Jumbo phages have attracted much attention by virtue of their extraordinary genome size and unusual aspects of biology. By performing a comparative genomics analysis of 224 jumbo phages, we suggest an objective inclusion criterion based on genome size distributions and present a synthetic overview of their manifold adaptations across major biological systems. By means of clustering and principal component analysis of the phyletic patterns of conserved genes, all known jumbo phages can be classified into three higher-order groups, which include both myoviral and siphoviral morphologies indicating multiple independent origins from smaller predecessors. Our study uncovers several under-appreciated or unreported aspects of the DNA replication, recombination, transcription and virion maturation systems. Leveraging sensitive sequence analysis methods, we identify novel protein-modifying enzymes that might help hijack the host-machinery. Focusing on host–virus conflicts, we detect strategies used to counter different wings of the bacterial immune system, such as cyclic nucleotide- and NAD+-dependent effector-activation, and prevention of superinfection during pseudolysogeny. We reconstruct the RNA-repair systems of jumbo phages that counter the consequences of RNA-targeting host effectors. These findings also suggest that several jumbo phage proteins provide a snapshot of the systems found in ancient replicons preceding the last universal ancestor of cellular life.
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Affiliation(s)
- Lakshminarayan M. Iyer
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA; (L.M.I.); (V.A.); (A.M.B.)
| | - Vivek Anantharaman
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA; (L.M.I.); (V.A.); (A.M.B.)
| | - Arunkumar Krishnan
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Berhampur, Odisha 760010, India;
| | - A. Maxwell Burroughs
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA; (L.M.I.); (V.A.); (A.M.B.)
| | - L. Aravind
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA; (L.M.I.); (V.A.); (A.M.B.)
- Correspondence:
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Andrews ESV, Rzoska-Smith E, Arcus VL. Post-transcriptional modulation of the SigF regulon in Mycobacterium smegmatis by the PhoH2 toxin-antitoxin. PLoS One 2020; 15:e0236551. [PMID: 32726339 PMCID: PMC7390352 DOI: 10.1371/journal.pone.0236551] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Accepted: 07/06/2020] [Indexed: 01/03/2023] Open
Abstract
PhoH2 proteins are highly conserved across bacteria and archaea yet their biological function is poorly characterised. We examined the growth profiles of Mycobacterium smegmatis strains mc2155 and mc2155 ΔphoH2 and observed the same growth profile and growth rate in a variety of conditions. In light of the comparable growth, we used RNAseq to provide a snapshot of the differences between the transcriptomes of M. smegmatis mc2155 and M. smegmatis mc2155 ΔphoH2 during normal growth. At 48 hours, elevated expression of the sigF regulon was observed in ΔphoH2 relative to wild type. In biochemical assays, PhoH2 showed activity toward sigF mRNA insinuating a role of PhoH2 in modulating the pool of sigF mRNA in the cell during normal growth, adding further complexity to the repertoire of reported mechanisms of post-translational regulation. Multiple copies of the preferred target site of PhoH2 were identified in loops of the sigF mRNA structure, leading us to propose a mechanism for the activity of PhoH2 that is initiated after assembly on specific single-stranded loops of RNA. We hypothesise that PhoH2 is a toxin-antitoxin that contributes to the regulation of SigF at a post-transcriptional level through targeted activity on sigF mRNA. This work presents the first evidence for post-transcriptional regulation of SigF along with the biological function of PhoH2 from M. smegmatis. This has implications for the highly conserved PhoH2 toxin-antitoxin module across the mycobacteria including the important human pathogen M. tuberculosis.
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Affiliation(s)
- Emma S. V. Andrews
- School of Science, Division of Health, Engineering, Computing and Science, University of Waikato, Hamilton, New Zealand
- * E-mail:
| | - Elizabeth Rzoska-Smith
- School of Science, Division of Health, Engineering, Computing and Science, University of Waikato, Hamilton, New Zealand
| | - Vickery L. Arcus
- School of Science, Division of Health, Engineering, Computing and Science, University of Waikato, Hamilton, New Zealand
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Andrews ESV, Arcus VL. PhoH2 proteins couple RNA helicase and RNAse activities. Protein Sci 2020; 29:883-892. [PMID: 31886915 DOI: 10.1002/pro.3814] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 12/20/2019] [Accepted: 12/23/2019] [Indexed: 01/29/2023]
Abstract
PhoH2 proteins are found in a very diverse range of microorganisms that span bacteria and archaea. These proteins are composed of two domains: an N-terminal PIN-domain fused with a C-terminal PhoH domain. Collectively this fusion functions as an RNA helicase and ribonuclease. In other genomic contexts, PINdomains and PhoHdomains are separate but adjacent suggesting association to achieve similar function. Exclusively among the mycobacteria, PhoH2 proteins are encoded in the genome with an upstream gene, phoAT, which is thought to play the role of an antitoxin (in place of the traditional VapB antitoxin that lies upstream of the 47 other PINdomains in the mycobacterial genome). This review examines PhoH2 proteins as a whole and describes the bioinformatics, biochemical, structural, and biological properties of the two domains that make up PhoH2: PIN and PhoH. We review the transcriptional regulators of phoH2 from two mycobacterial species and speculate on the function of PhoH2 proteins in the context of a Type II toxin-antitoxin system which are thought to play a role in the stress response in bacteria.
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Affiliation(s)
- Emma S V Andrews
- School of Science, Division of Health, Engineering, Computing and Science, University of Waikato, Hamilton, New Zealand
| | - Vickery L Arcus
- School of Science, Division of Health, Engineering, Computing and Science, University of Waikato, Hamilton, New Zealand
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