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Halfmann CT, Scott KL, Sears RM, Roux KJ. Mechanisms by which barrier-to-autointegration factor regulates dynamics of nucleocytoplasmic leakage and membrane repair following nuclear envelope rupture. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.21.572811. [PMID: 38187776 PMCID: PMC10769424 DOI: 10.1101/2023.12.21.572811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
The nuclear envelope (NE) creates a barrier between the cytosol and nucleus during interphase that is key for cellular compartmentalization and protecting genomic DNA. NE rupture can expose genomic DNA to the cytosol and allow admixture of the nuclear and cytosolic constituents, a proposed mechanism of cancer and NE-associated diseases. Barrier-to-autointegration factor (BAF) is a DNA-binding protein that localizes to NE ruptures where it recruits LEM-domain proteins, A-type lamins, and participates in rupture repair. To further reveal the mechanisms by which BAF responds to and aids in repairing NE ruptures, we investigated known properties of BAF including LEM domain binding, lamin binding, compartmentalization, phosphoregulation of DNA binding, and BAF dimerization. We demonstrate that it is the cytosolic population of BAF that functionally repairs NE ruptures, and phosphoregulation of BAF's DNA-binding that enables its ability to facilitate that repair. Interestingly, BAF's LEM or lamin binding activity appears dispensable for its role in functional repair. Furthermore, we demonstrate that BAF functions to reduce the extent of leakage though NE ruptures, suggesting that BAF effectively forms a diffusion barrier prior to NE repair. Collectively, these results enhances our knowledge of the mechanisms by which BAF responds to NE ruptures and facilitates their repair.
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Affiliation(s)
| | - Kelsey L. Scott
- Enabling Technologies Group, Sanford Research, Sioux Falls SD
| | - Rhiannon M. Sears
- Enabling Technologies Group, Sanford Research, Sioux Falls SD
- Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD
| | - Kyle J. Roux
- Enabling Technologies Group, Sanford Research, Sioux Falls SD
- Department of Pediatrics, Sanford School of Medicine, University of South Dakota, Sioux Falls SD
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2
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Linville AC, Rico AB, Teague H, Binsted LE, Smith GL, Albarnaz JD, Wiebe MS. Dysregulation of Cellular VRK1, BAF, and Innate Immune Signaling by the Vaccinia Virus B12 Pseudokinase. J Virol 2022; 96:e0039822. [PMID: 35543552 PMCID: PMC9175622 DOI: 10.1128/jvi.00398-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 04/18/2022] [Indexed: 11/20/2022] Open
Abstract
Poxvirus proteins remodel signaling throughout the cell by targeting host enzymes for inhibition and redirection. Recently, it was discovered that early in infection the vaccinia virus (VACV) B12 pseudokinase copurifies with the cellular kinase VRK1, a proviral factor, in the nucleus. Although the formation of this complex correlates with inhibition of cytoplasmic VACV DNA replication and likely has other downstream signaling consequences, the molecular mechanisms involved are poorly understood. Here, we further characterize how B12 and VRK1 regulate one another during poxvirus infection. First, we demonstrate that B12 is stabilized in the presence of VRK1 and that VRK1 and B12 coinfluence their respective solubility and subcellular localization. In this regard, we find that B12 promotes VRK1 colocalization with cellular DNA during mitosis and that B12 and VRK1 may be tethered cooperatively to chromatin. Next, we observe that the C-terminal tail of VRK1 is unnecessary for B12-VRK1 complex formation or its proviral activity. Interestingly, we identify a point mutation of B12 capable of abrogating interaction with VRK1 and which renders B12 nonrepressive during infection. Lastly, we investigated the influence of B12 on the host factor BAF and antiviral signaling pathways and find that B12 triggers redistribution of BAF from the cytoplasm to the nucleus. In addition, B12 increases DNA-induced innate immune signaling, revealing a new functional consequence of the B12 pseudokinase. Together, this study characterizes the multifaceted roles B12 plays during poxvirus infection that impact VRK1, BAF, and innate immune signaling. IMPORTANCE Protein pseudokinases comprise a considerable fraction of the human kinome, as well as other forms of life. Recent studies have demonstrated that their lack of key catalytic residues compared to their kinase counterparts does not negate their ability to intersect with molecular signal transduction. While the multifaceted roles pseudokinases can play are known, their contribution to virus infection remains understudied. Here, we further characterize the mechanism of how the VACV B12 pseudokinase and human VRK1 kinase regulate one another in the nucleus during poxvirus infection and inhibit VACV DNA replication. We find that B12 disrupts regulation of VRK1 and its downstream target BAF, while also enhancing DNA-dependent innate immune signaling. Combined with previous data, these studies contribute to the growing field of nuclear pathways targeted by poxviruses and provide evidence of unexplored roles of B12 in the activation of antiviral immunity.
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Affiliation(s)
- Alexandria C. Linville
- Nebraska Center for Virology, University of Nebraska, Lincoln, Nebraska, USA
- School of Biological Sciences, University of Nebraska, Lincoln, Nebraska, USA
| | - Amber B. Rico
- Nebraska Center for Virology, University of Nebraska, Lincoln, Nebraska, USA
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska, Lincoln, Nebraska, USA
| | - Helena Teague
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Lucy E. Binsted
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Geoffrey L. Smith
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Jonas D. Albarnaz
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Matthew S. Wiebe
- Nebraska Center for Virology, University of Nebraska, Lincoln, Nebraska, USA
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska, Lincoln, Nebraska, USA
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3
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Abstract
Poxviruses, of which vaccinia virus is the prototype, are a large family of double-stranded DNA viruses that replicate exclusively in the cytoplasm of infected cells. This physical and genetic autonomy from the host cell nucleus necessitates that these viruses encode most, if not all, of the proteins required for replication in the cytoplasm. In this review, we follow the life of the viral genome through space and time to address some of the unique challenges that arise from replicating a 195-kb DNA genome in the cytoplasm. We focus on how the genome is released from the incoming virion and deposited into the cytoplasm; how the endoplasmic reticulum is reorganized to form a replication factory, thereby compartmentalizing and helping to protect the replicating genome from immune sensors; how the cellular milieu is tailored to support high-fidelity replication of the genome; and finally, how newly synthesized genomes are faithfully and specifically encapsidated into new virions. Expected final online publication date for the Annual Review of Virology, Volume 9 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Matthew D Greseth
- Department of Biochemistry and Molecular Biology, The Medical University of South Carolina, Charleston, South Carolina, USA;
| | - Paula Traktman
- Department of Biochemistry and Molecular Biology, The Medical University of South Carolina, Charleston, South Carolina, USA; .,Department of Microbiology and Immunology, The Medical University of South Carolina, Charleston, South Carolina, USA
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Burger M, Kaelin S, Leroux J. The TFAMoplex-Conversion of the Mitochondrial Transcription Factor A into a DNA Transfection Agent. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2104987. [PMID: 35038234 PMCID: PMC8922101 DOI: 10.1002/advs.202104987] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Indexed: 06/14/2023]
Abstract
Non-viral gene delivery agents, such as cationic lipids, polymers, and peptides, mainly rely on charge-based and hydrophobic interactions for the condensation of DNA molecules into nanoparticles. The human protein mitochondrial transcription factor A (TFAM), on the other hand, has evolved to form nanoparticles with DNA through highly specific protein-protein and protein-DNA interactions. Here, the properties of TFAM are repurposed to create a DNA transfection agent by means of protein engineering. TFAM is covalently fused to Listeria monocytogenes phospholipase C (PLC), an enzyme that lyses lipid membranes under acidic conditions, to enable endosomal escape and human vaccinia-related kinase 1 (VRK1), which is intended to protect the DNA from cytoplasmic defense mechanisms. The TFAM/DNA complexes (TFAMoplexes) are stabilized by cysteine point mutations introduced rationally in the TFAM homodimerization site, resulting in particles, which show maximal activity when formed in 80% serum and transfect HeLa cells in vitro after 30 min of incubation under challenging cell culture conditions. The herein developed TFAM-based DNA scaffolds combine interesting characteristics in an easy-to-use system and can be readily expanded with further protein factors. This makes the TFAMoplex a promising tool in protein-based gene delivery.
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Affiliation(s)
- Michael Burger
- Swiss Federal Institute of Technology Zurich (ETHZ)Department of Chemistry and Applied BiosciencesInstitute of Pharmaceutical SciencesVladimir‐Prelog‐Weg 3Zurich8093Switzerland
| | - Seraina Kaelin
- Swiss Federal Institute of Technology Zurich (ETHZ)Department of Chemistry and Applied BiosciencesInstitute of Pharmaceutical SciencesVladimir‐Prelog‐Weg 3Zurich8093Switzerland
| | - Jean‐Christophe Leroux
- Swiss Federal Institute of Technology Zurich (ETHZ)Department of Chemistry and Applied BiosciencesInstitute of Pharmaceutical SciencesVladimir‐Prelog‐Weg 3Zurich8093Switzerland
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5
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Transfected plasmid DNA is incorporated into the nucleus via nuclear envelope reformation at telophase. Commun Biol 2022; 5:78. [PMID: 35058555 PMCID: PMC8776997 DOI: 10.1038/s42003-022-03021-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Accepted: 12/27/2021] [Indexed: 12/15/2022] Open
Abstract
AbstractDNA transfection is an important technology in life sciences, wherein nuclear entry of DNA is necessary to express exogenous DNA. Non-viral vectors and their transfection reagents are useful as safe transfection tools. However, they have no effect on the transfection of non-proliferating cells, the reason for which is not well understood. This study elucidates the mechanism through which transfected DNA enters the nucleus for gene expression. To monitor the behavior of transfected DNA, we introduce plasmid bearing lacO repeats and RFP-coding sequences into cells expressing GFP-LacI and observe plasmid behavior and RFP expression in living cells. RFP expression appears only after mitosis. Electron microscopy reveals that plasmids are wrapped with nuclear envelope (NE)‒like membranes or associated with chromosomes at telophase. The depletion of BAF, which is involved in NE reformation, delays plasmid RFP expression. These results suggest that transfected DNA is incorporated into the nucleus during NE reformation at telophase.
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Marcelot A, Petitalot A, Ropars V, Le Du MH, Samson C, Dubois S, Hoffmann G, Miron S, Cuniasse P, Marquez JA, Thai R, Theillet FX, Zinn-Justin S. Di-phosphorylated BAF shows altered structural dynamics and binding to DNA, but interacts with its nuclear envelope partners. Nucleic Acids Res 2021; 49:3841-3855. [PMID: 33744941 PMCID: PMC8053085 DOI: 10.1093/nar/gkab184] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Revised: 02/05/2021] [Accepted: 03/06/2021] [Indexed: 02/07/2023] Open
Abstract
Barrier-to-autointegration factor (BAF), encoded by the BANF1 gene, is an abundant and ubiquitously expressed metazoan protein that has multiple functions during the cell cycle. Through its ability to cross-bridge two double-stranded DNA (dsDNA), it favours chromosome compaction, participates in post-mitotic nuclear envelope reassembly and is essential for the repair of large nuclear ruptures. BAF forms a ternary complex with the nuclear envelope proteins lamin A/C and emerin, and its interaction with lamin A/C is defective in patients with recessive accelerated aging syndromes. Phosphorylation of BAF by the vaccinia-related kinase 1 (VRK1) is a key regulator of BAF localization and function. Here, we demonstrate that VRK1 successively phosphorylates BAF on Ser4 and Thr3. The crystal structures of BAF before and after phosphorylation are extremely similar. However, in solution, the extensive flexibility of the N-terminal helix α1 and loop α1α2 in BAF is strongly reduced in di-phosphorylated BAF, due to interactions between the phosphorylated residues and the positively charged C-terminal helix α6. These regions are involved in DNA and lamin A/C binding. Consistently, phosphorylation causes a 5000-fold loss of affinity for dsDNA. However, it does not impair binding to lamin A/C Igfold domain and emerin nucleoplasmic region, which leaves open the question of the regulation of these interactions.
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Affiliation(s)
- Agathe Marcelot
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette Cedex, France
| | - Ambre Petitalot
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette Cedex, France
| | - Virginie Ropars
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette Cedex, France
| | - Marie-Hélène Le Du
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette Cedex, France
| | - Camille Samson
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette Cedex, France
| | | | - Guillaume Hoffmann
- High Throughput Crystallization Lab, EMBL Grenoble Outstation, Grenoble Cedex, France
| | - Simona Miron
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette Cedex, France
| | - Philippe Cuniasse
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette Cedex, France
| | - Jose Antonio Marquez
- High Throughput Crystallization Lab, EMBL Grenoble Outstation, Grenoble Cedex, France
| | | | - François-Xavier Theillet
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette Cedex, France
| | - Sophie Zinn-Justin
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette Cedex, France
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7
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Halfmann CT, Roux KJ. Barrier-to-autointegration factor: a first responder for repair of nuclear ruptures. Cell Cycle 2021; 20:647-660. [PMID: 33678126 DOI: 10.1080/15384101.2021.1892320] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
The nuclear envelope (NE) is a critical barrier between the cytosol and nucleus that is key for compartmentalization within the cell and serves an essential role in organizing and protecting genomic DNA. Rupturing of the NE through loss of constitutive NE proteins and/or mechanical force applied to the nucleus results in the unregulated mixing of cytosolic and nuclear compartments, leading to DNA damage and genomic instability. Nuclear rupture has recently gained interest as a mechanism that may participate in various NE-associated diseases as well as cancer. Remarkably, these rupturing events are often transient, with cells being capable of rapidly repairing nuclear ruptures. Recently, we identified Barrier-to-Autointegration Factor (BAF), a DNA-binding protein involved in post-mitotic NE reformation and cytosolic viral regulation, as an essential protein for nuclear rupture repair. During interphase, the highly mobile cytosolic BAF is primed to monitor for a compromised NE by rapidly binding to newly exposed nuclear DNA and subsequently recruiting the factors necessary for NE repair. This review highlights the recent findings of BAF's roles in rupture repair, and offers perspectives on how regulatory factors that control BAF activity may potentially alter the cellular response to nuclear ruptures and how BAF may participate in human disease.
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Affiliation(s)
| | - Kyle J Roux
- Enabling Technologies Group, Sanford Research, Sioux Falls, SD, USA.,Department of Pediatrics, Sanford School of Medicine, University of South Dakota, Sioux Falls, SD, USA
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8
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The Vaccinia Virus B12 Pseudokinase Represses Viral Replication via Interaction with the Cellular Kinase VRK1 and Activation of the Antiviral Effector BAF. J Virol 2021; 95:JVI.02114-20. [PMID: 33177193 DOI: 10.1128/jvi.02114-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 10/31/2020] [Indexed: 11/20/2022] Open
Abstract
The poxviral B1 and B12 proteins are a homologous kinase-pseudokinase pair, which modulates a shared host pathway governing viral DNA replication and antiviral defense. While the molecular mechanisms involved are incompletely understood, B1 and B12 seem to intersect with signaling processes mediated by their cellular homologs termed the vaccinia-related kinases (VRKs). In this study, we expand upon our previous characterization of the B1-B12 signaling axis to gain insights into B12 function. We begin our studies by demonstrating that modulation of B12 repressive activity is a conserved function of B1 orthologs from divergent poxviruses. Next, we characterize the protein interactome of B12 using multiple cell lines and expression systems and discover that the cellular kinase VRK1 is a highly enriched B12 interactor. Using complementary VRK1 knockdown and overexpression assays, we first demonstrate that VRK1 is required for the rescue of a B1-deleted virus upon mutation of B12. Second, we find that VRK1 overexpression is sufficient to overcome repressive B12 activity during B1-deleted virus replication. Interestingly, we also evince that B12 interferes with the ability of VRK1 to phosphoinactivate the host defense protein BAF. Thus, B12 restricts vaccinia virus DNA accumulation in part by repressing the ability of VRK1 to inactivate BAF. Finally, these data establish that a B12-VRK1-BAF signaling axis forms during vaccinia virus infection and is modulated via kinases B1 and/or VRK2. These studies provide novel insights into the complex mechanisms that poxviruses use to hijack homologous cellular signaling pathways during infection.IMPORTANCE Viruses from diverse families encode both positive and negative regulators of viral replication. While their functions can sometimes be enigmatic, investigation of virus-encoded, negative regulators of viral replication has revealed fascinating aspects of virology. Studies of poxvirus-encoded genes have largely concentrated on positive regulators of their replication; however, examples of fitness gains attributed to poxvirus gene loss suggests that negative regulators of poxvirus replication also impact infection dynamics. This study focuses on the vaccinia B12 pseudokinase, a protein capable of inhibiting vaccinia DNA replication. Here, we elucidate the mechanisms by which B12 inhibits vaccinia DNA replication, demonstrating that B12 activates the antiviral protein BAF by inhibiting the activity of VRK1, a cellular modulator of BAF. Combined with previous data, these studies provide evidence that poxviruses govern their replication by employing both positive and negative regulators of viral replication.
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9
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Liu LK, Gao Y, Gao RL, Li DL, Zhang QX, Wang KJ, Liu HP. A barrier-to-autointegration factor promotes white spot syndrome virus infection in a crustacean Cherax quadricarinatus. FISH & SHELLFISH IMMUNOLOGY 2020; 105:244-252. [PMID: 32693160 DOI: 10.1016/j.fsi.2020.07.031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 07/09/2020] [Accepted: 07/14/2020] [Indexed: 06/11/2023]
Abstract
Barrier-to-autointegration factor (BAF) is a highly conserved DNA binding protein that participates in a variety of biological processes such as transcription, epigenetic regulation and antiviral immunity in vertebrates. However, the function of BAF is poorly understood in crustaceans. In this study, we identified a barrier-to-autointegration factor (CqBAF) from red claw crayfish Cherax quadricarinatus, which was responsive to white spot syndrome virus (WSSV) infection. The full-length cDNA sequence of CqBAF was 544 bp, including an open reading frame of 273 bp encoding 90 amino acids, a 107 bp of 5'-Untranslated Regions (5'-UTR) and a 164 bp of 3'-UTR. Gene expression analysis showed that CqBAF was distributed in all tissues examined with the highest expression in the crayfish haematopietic tissue (Hpt), which protein expression was also significantly up-regulated by WSSV infection in Hpt cells. Furthermore, the transcripts of both an immediate early gene IE1 and a late envelope protein gene VP28 of WSSV were clearly reduced in Hpt cells after gene silencing of CqBAF. Importantly, the promoter activity of two immediate early genes of WSSV, including WSV051 and IE1, was strongly enhanced by the increased phosphorylation of CqBAF, which also facilitated the accumulation of CqBAF protein in the cytoplasm of Sf9 cells. Taken together, these data suggest that CqBAF is likely to increase the replication of WSSV by promoting the transcription of viral immediate early genes, probably regulated by phosphorylation of CqBAF, which sheds new light on the molecular mechanism of WSSV infection.
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Affiliation(s)
- Ling-Ke Liu
- State Key Laboratory of Marine Environmental Science, State-Province Joint Engineering Laboratory of Marine Bioproducts and Technology, College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361102, Fujian, China
| | - Yan Gao
- State Key Laboratory of Marine Environmental Science, State-Province Joint Engineering Laboratory of Marine Bioproducts and Technology, College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361102, Fujian, China
| | - Rui-Lin Gao
- State Key Laboratory of Marine Environmental Science, State-Province Joint Engineering Laboratory of Marine Bioproducts and Technology, College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361102, Fujian, China
| | - Dong-Li Li
- State Key Laboratory of Marine Environmental Science, State-Province Joint Engineering Laboratory of Marine Bioproducts and Technology, College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361102, Fujian, China
| | - Qiu-Xia Zhang
- State Key Laboratory of Marine Environmental Science, State-Province Joint Engineering Laboratory of Marine Bioproducts and Technology, College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361102, Fujian, China
| | - Ke-Jian Wang
- State Key Laboratory of Marine Environmental Science, State-Province Joint Engineering Laboratory of Marine Bioproducts and Technology, College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361102, Fujian, China
| | - Hai-Peng Liu
- State Key Laboratory of Marine Environmental Science, State-Province Joint Engineering Laboratory of Marine Bioproducts and Technology, College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361102, Fujian, China; Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology (Qingdao), China.
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10
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Sears RM, Roux KJ. Diverse cellular functions of barrier-to-autointegration factor and its roles in disease. J Cell Sci 2020; 133:133/16/jcs246546. [PMID: 32817163 DOI: 10.1242/jcs.246546] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Barrier-to-autointegration factor (BAF; encoded by BANF1) is a small highly conserved, ubiquitous and self-associating protein that coordinates with numerous binding partners to accomplish several key cellular processes. By interacting with double-stranded DNA, histones and various other nuclear proteins, including those enriched at the nuclear envelope, BAF appears to be essential for replicating cells to protect the genome and enable cell division. Cellular processes, such as innate immunity, post-mitotic nuclear reformation, repair of interphase nuclear envelope rupture, genomic regulation, and the DNA damage and repair response have all been shown to depend on BAF. This Review focuses on the regulation of the numerous interactions of BAF, which underlie the mechanisms by which BAF accomplishes its essential cellular functions. We will also discuss how perturbation of BAF function may contribute to human disease.
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Affiliation(s)
- Rhiannon M Sears
- Enabling Technologies Group, Sanford Research, Sioux Falls, SD 57104, USA.,Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069, USA
| | - Kyle J Roux
- Enabling Technologies Group, Sanford Research, Sioux Falls, SD 57104, USA .,Department of Pediatrics, Sanford School of Medicine, University of South Dakota, Sioux Falls, SD 57069, USA
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11
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The Vaccinia Virus (VACV) B1 and Cellular VRK2 Kinases Promote VACV Replication Factory Formation through Phosphorylation-Dependent Inhibition of VACV B12. J Virol 2019; 93:JVI.00855-19. [PMID: 31341052 DOI: 10.1128/jvi.00855-19] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 07/16/2019] [Indexed: 01/08/2023] Open
Abstract
Comparative examination of viral and host protein homologs reveals novel mechanisms governing downstream signaling effectors of both cellular and viral origin. The vaccinia virus B1 protein kinase is involved in promoting multiple facets of the virus life cycle and is a homolog of three conserved cellular enzymes called vaccinia virus-related kinases (VRKs). Recent evidence indicates that B1 and VRK2 mediate a common pathway that is largely uncharacterized but appears independent of previous VRK substrates. Interestingly, separate studies described a novel role for B1 in inhibiting vaccinia virus protein B12, which otherwise impedes an early event in the viral lifecycle. Herein, we characterize the B1/VRK2 signaling axis to better understand their shared functions. First, we demonstrate that vaccinia virus uniquely requires VRK2 for viral replication in the absence of B1, unlike other DNA viruses. Employing loss-of-function analysis, we demonstrate that vaccinia virus's dependence on VRK2 is only observed in the presence of B12, suggesting that B1 and VRK2 share a pathway controlling B12. Moreover, we substantiate a B1/VRK2/B12 signaling axis by examining coprecipitation of B12 by B1 and VRK2. Employing execution point analysis, we reveal that virus replication proceeds normally through early protein translation and uncoating but stalls at replication factory formation in the presence of B12 activity. Finally, structure/function analyses of B1 and VRK2 demonstrate that enzymatic activity is essential for B1 or VRK2 to inhibit B12. Together, these data provide novel insights into B1/VRK signaling coregulation and support a model in which these enzymes modulate B12 in a phosphorylation-dependent manner.IMPORTANCE Constraints placed on viral genome size require that these pathogens must employ sophisticated, yet parsimonious mechanisms to effectively integrate with host cell signaling pathways. Poxviruses are no exception and employ several methods to balance these goals, including encoding single proteins that impact multiple downstream pathways. This study focuses on the vaccinia virus B1 protein kinase, an enzyme that promotes virus replication at multiple phases of the viral lifecycle. Herein, we demonstrate that in addition to its previously characterized functions, B1 inhibits vaccinia virus B12 protein via a phosphorylation-dependent mechanism and that this function of B1 can be complemented by the cellular B1 homolog VRK2. Combined with previous data implicating functional overlap between B1 and an additional cellular B1 homolog, VRK1, these data provide evidence of how poxviruses can be multifaceted in their mimicry of cellular proteins through the consolidation of functions of both VRK1 and VRK2 within the viral B1 protein kinase.
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12
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Halfmann CT, Sears RM, Katiyar A, Busselman BW, Aman LK, Zhang Q, O'Bryan CS, Angelini TE, Lele TP, Roux KJ. Repair of nuclear ruptures requires barrier-to-autointegration factor. J Cell Biol 2019; 218:2136-2149. [PMID: 31147383 PMCID: PMC6605789 DOI: 10.1083/jcb.201901116] [Citation(s) in RCA: 104] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 04/29/2019] [Accepted: 05/14/2019] [Indexed: 12/31/2022] Open
Abstract
Cell nuclei rupture following exposure to mechanical force and/or upon weakening of nuclear integrity, but nuclear ruptures are repairable. Barrier-to-autointegration factor (BAF), a small DNA-binding protein, rapidly localizes to nuclear ruptures; however, its role at these rupture sites is unknown. Here, we show that it is predominantly a nonphosphorylated cytoplasmic population of BAF that binds nuclear DNA to rapidly and transiently localize to the sites of nuclear rupture, resulting in BAF accumulation in the nucleus. BAF subsequently recruits transmembrane LEM-domain proteins, causing their accumulation at rupture sites. Loss of BAF impairs recruitment of LEM-domain proteins and nuclear envelope membranes to nuclear rupture sites and prevents nuclear envelope barrier function restoration. Simultaneous depletion of multiple LEM-domain proteins similarly inhibits rupture repair. LEMD2 is required for recruitment of the ESCRT-III membrane repair machinery to ruptures; however, neither LEMD2 nor ESCRT-III is required to repair ruptures. These results reveal a new role for BAF in the response to and repair of nuclear ruptures.
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Affiliation(s)
| | - Rhiannon M Sears
- Enabling Technologies Group, Sanford Research, Sioux Falls, SD
- Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD
| | - Aditya Katiyar
- Department of Chemical Engineering, University of Florida, Gainesville, FL
| | - Brook W Busselman
- Enabling Technologies Group, Sanford Research, Sioux Falls, SD
- Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD
| | - London K Aman
- Enabling Technologies Group, Sanford Research, Sioux Falls, SD
| | - Qiao Zhang
- Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL
| | - Christopher S O'Bryan
- Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL
| | - Thomas E Angelini
- Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL
- Institute for Cell and Tissue Science and Engineering, University of Florida, Gainesville, FL
| | - Tanmay P Lele
- Department of Chemical Engineering, University of Florida, Gainesville, FL
- Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL
- Institute for Cell and Tissue Science and Engineering, University of Florida, Gainesville, FL
| | - Kyle J Roux
- Enabling Technologies Group, Sanford Research, Sioux Falls, SD
- Department of Pediatrics, Sanford School of Medicine, University of South Dakota, Sioux Falls, SD
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13
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Sun YZ, Li JF, Wei ZD, Jiang HH, Hong YX, Zheng S, Qi RQ, Gao XH. Proteomic and bioinformatic analysis of condyloma acuminata: mild hyperthermia treatment reveals compromised HPV infectivity of keratinocytes via regulation of metabolism, differentiation and anti-viral responses. Int J Hyperthermia 2019; 36:383-393. [PMID: 30909744 DOI: 10.1080/02656736.2019.1578420] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Hyperthermia has proved successful in treating cutaneous human papillomavirus infectious diseases such as plantar wart and condyloma acuminata (CA). Moreover, this treatment provides improved therapeutic efficacy in these conditions as compared with conventional therapies. OBJECTIVES To investigate the global proteome changes in CA in response to hyperthermia and achieve a better understanding of the mechanisms of hyperthermia therapy against HPV-infectious diseases. METHODS CA tissue was obtained from patients undergoing pathological examinations. Diagnosis was verified as based on results of both HE staining and HPV-DNA PCR assay. Hyperthermia was achieved with a 44 °C water bath. Differentially expressed proteins (DEPs) were identified by iTRAQ labeling, SCX chromatography and LC-MS/MS assay. Validation of proteomic results was performed using real-time qPCR and western blot, while bioinformatic analysis of DEPs was accomplished by R 3.4.1, STRING and Cytoscape softwares. RESULTS In response to hyperthermia, a total of 102 DEPs were identified with 37 being upregulated and 65 downregulated. Among these DEPs, hyperthermia induced proteins involved with anti-viral processes such as OAS1, MX1, BANF1, CANX and AP1S1, whereas it inhibited proteins that participated in cellular metabolism, such as GALT, H6PD, EXOSC4 and EXOSC6; protein translation, such as RPS4Y1; as well as keratinocyte differentiation, such as KRT5, KRT27, KRT75, KRT76 and H2AFY2. CONCLUSIONS Hyperthermia inhibited enzymes and molecules responsible for metabolism modulation and keratinocyte differentiation in CA tissue, whereas it promoted factors involved in anti-viral responses. Such effects may, in part, contribute to the efficacy of local hyperthermia therapy against HPV infection.
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Affiliation(s)
- Yu-Zhe Sun
- a Graduate School, China Medical University , Shenyang , China.,b Department of Dermatology , The First Hospital of China Medical University and Key Laboratory of Immunodermatology, Ministry of Health and Ministry of Education , Shenyang , China
| | - Jia-Feng Li
- a Graduate School, China Medical University , Shenyang , China.,c Department of Pathology , The First Hospital of China Medical University , Shenyang , China
| | - Zhen-Dong Wei
- d Department of Dermatology , the 2nd Affiliated Hospital of Dalian Medical University , Dalian , China
| | - Hang-Hang Jiang
- b Department of Dermatology , The First Hospital of China Medical University and Key Laboratory of Immunodermatology, Ministry of Health and Ministry of Education , Shenyang , China
| | - Yu-Xiao Hong
- b Department of Dermatology , The First Hospital of China Medical University and Key Laboratory of Immunodermatology, Ministry of Health and Ministry of Education , Shenyang , China
| | - Song Zheng
- b Department of Dermatology , The First Hospital of China Medical University and Key Laboratory of Immunodermatology, Ministry of Health and Ministry of Education , Shenyang , China
| | - Rui-Qun Qi
- b Department of Dermatology , The First Hospital of China Medical University and Key Laboratory of Immunodermatology, Ministry of Health and Ministry of Education , Shenyang , China
| | - Xing-Hua Gao
- a Graduate School, China Medical University , Shenyang , China.,b Department of Dermatology , The First Hospital of China Medical University and Key Laboratory of Immunodermatology, Ministry of Health and Ministry of Education , Shenyang , China
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14
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Olson AT, Wang Z, Rico AB, Wiebe MS. A poxvirus pseudokinase represses viral DNA replication via a pathway antagonized by its paralog kinase. PLoS Pathog 2019; 15:e1007608. [PMID: 30768651 PMCID: PMC6395007 DOI: 10.1371/journal.ppat.1007608] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 02/28/2019] [Accepted: 01/31/2019] [Indexed: 12/26/2022] Open
Abstract
Poxviruses employ sophisticated, but incompletely understood, signaling pathways that engage cellular defense mechanisms and simultaneously ensure viral factors are modulated properly. For example, the vaccinia B1 protein kinase plays a vital role in inactivating the cellular antiviral factor BAF, and likely orchestrates other pathways as well. In this study, we utilized experimental evolution of a B1 deletion virus to perform an unbiased search for suppressor mutations and identify novel pathways involving B1. After several passages of the ΔB1 virus we observed a robust increase in viral titer of the adapted virus. Interestingly, our characterization of the adapted viruses reveals that mutations correlating with a loss of function of the vaccinia B12 pseudokinase provide a striking fitness enhancement to this virus. In support of predictions that reductive evolution is a driver of poxvirus adaptation, this is clear experimental evidence that gene loss can be of significant benefit. Next, we present multiple lines of evidence demonstrating that expression of full length B12 leads to a fitness reduction in viruses with a defect in B1, but has no apparent impact on wild-type virus or other mutant poxviruses. From these data we infer that B12 possesses a potent inhibitory activity that can be masked by the presence of the B1 kinase. Further investigation of B12 attributes revealed that it primarily localizes to the nucleus, a characteristic only rarely found among poxviral proteins. Surprisingly, BAF phosphorylation is reduced under conditions in which B12 is present in infected cells without B1, indicating that B12 may function in part by enhancing antiviral activity of BAF. Together, our studies of B1 and B12 present novel evidence that a paralogous kinase-pseudokinase pair can exhibit a unique epistatic relationship in a virus, perhaps serving to enhance B1 conservation during poxvirus evolution and to orchestrate yet-to-be-discovered nuclear events during infection.
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Affiliation(s)
- Annabel T. Olson
- Nebraska Center for Virology, University of Nebraska, Lincoln, NE, United States of America
- School of Biological Sciences, University of Nebraska, Lincoln, NE, United States of America
| | - Zhigang Wang
- Nebraska Center for Virology, University of Nebraska, Lincoln, NE, United States of America
| | - Amber B. Rico
- Nebraska Center for Virology, University of Nebraska, Lincoln, NE, United States of America
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska, Lincoln, NE, United States of America
| | - Matthew S. Wiebe
- Nebraska Center for Virology, University of Nebraska, Lincoln, NE, United States of America
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska, Lincoln, NE, United States of America
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15
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Li J, Hu B, Fang L, Gao Y, Shi S, He H, Liu X, Yuan C. Barrier-to-autointegration factor 1: A novel biomarker for gastric cancer. Oncol Lett 2018; 16:6488-6494. [PMID: 30405787 PMCID: PMC6202538 DOI: 10.3892/ol.2018.9432] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Accepted: 06/26/2018] [Indexed: 12/30/2022] Open
Abstract
China is a country with a high incidence of gastric cancer (GC), where the GC incidence and the resultant mortality rates account for 50% of those worldwide. Surgical resection remains the primary treatment for GC. However, postoperative patients have a poor prognosis as the majority of patients present with metastases at the time of diagnosis. Therefore, the identification of novel treatment targets is required. The present study aimed to determine the effects of barrier-to-autointegration factor 1 (BANF1) on the clinical features and prognosis of GC, which may aid in discovering a novel tumor diagnostic biomarker and treatment target. The BANF1 gene expression profiles for normal and gastric tumor tissues were downloaded from the Gene Expression Omnibus GSE54129 data set to analyse the expression of BANF1 at the mRNA levels. Then, online survival analysis was performed using the GC database with the Kaplan-Meier Plotter (http://kmplot.com/analysis/) data. To examine the association between BANF1 and clinical features and prognosis, 132 postoperative GC pathological specimens were collected for immunohistochemical analyses. In the GSE54129 data sets, BANF1 expression at the mRNA level was significantly higher in the tumor tissue compared with that in the normal tissue. The same result was obtained in following the immunohistochemical analyses. In addition, BANF1 expression was associated with the patient age, tumor differentiation and infiltration depth. The survival time of BANF1 high-expression patients was shorter compared with that of the low-expression patients, and tumor differentiation status and tumor node metastasis stage were independent prognostic factors of the overall survival of patients with GC. The results of the present study suggest that BANF1 is associated with the clinical features and prognosis of GC. It may be a novel indicator of tumor prognosis and a potential therapeutic target for GC.
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Affiliation(s)
- Junjun Li
- Department of Oncology, The First Affiliated Hospital of Jinzhou Medical University, Jinzhou, Liaoning 121000, P.R. China
| | - Bingbing Hu
- Department of Infectious Diseases, The Third Affiliated Hospital of Xinxiang Medical University, Xinxiang, Henan 453000, P.R. China
| | - Lei Fang
- Department of Pathology and Pathophysiology, Jinzhou Medical University, Jinzhou, Liaoning 121001, P.R. China
| | - Yang Gao
- Department of Oncology, The First Affiliated Hospital of Jinzhou Medical University, Jinzhou, Liaoning 121000, P.R. China
| | - Shuai Shi
- Department of Pathology and Pathophysiology, Jinzhou Medical University, Jinzhou, Liaoning 121001, P.R. China
| | - Haoyu He
- Department of Oncology, The First Affiliated Hospital of Jinzhou Medical University, Jinzhou, Liaoning 121000, P.R. China
| | - Xiaomei Liu
- Department of Oncology, The First Affiliated Hospital of Jinzhou Medical University, Jinzhou, Liaoning 121000, P.R. China
| | - Caijun Yuan
- Department of Oncology, The First Affiliated Hospital of Jinzhou Medical University, Jinzhou, Liaoning 121000, P.R. China
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Deletion of the Vaccinia Virus B1 Kinase Reveals Essential Functions of This Enzyme Complemented Partly by the Homologous Cellular Kinase VRK2. J Virol 2017; 91:JVI.00635-17. [PMID: 28515294 DOI: 10.1128/jvi.00635-17] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 05/10/2017] [Indexed: 12/30/2022] Open
Abstract
The vaccinia virus B1 kinase is highly conserved among poxviruses and is essential for the viral life cycle. B1 exhibits a remarkable degree of similarity to vaccinia virus-related kinases (VRKs), a family of cellular kinases, suggesting that the viral enzyme has evolved to mimic VRK activity. Indeed, B1 and VRKs have been demonstrated to target a shared substrate, the DNA binding protein BAF, elucidating a signaling pathway important for both mitosis and the antiviral response. In this study, we further characterize the role of B1 during vaccinia infection to gain novel insights into its regulation and integration with cellular signaling pathways. We begin by describing the construction and characterization of the first B1 deletion virus (vvΔB1) produced using a complementing cell line expressing the viral kinase. Examination of vvΔB1 revealed that B1 is critical for the production of infectious virions in various cell types and is sufficient for BAF phosphorylation. Interestingly, the severity of the defect in DNA replication following the loss of B1 varied between cell types, leading us to posit that cellular VRKs partly complement for the absence of B1 in some cell lines. Using cell lines devoid of either VRK1 or VRK2, we tested this hypothesis and discovered that VRK2 expression facilitates DNA replication and allows later stages of the viral life cycle to proceed in the absence of B1. Finally, we present evidence that the impact of VRK2 on vaccinia virus is largely independent of BAF phosphorylation. These data support a model in which B1 and VRK2 share additional substrates important for the replication of cytoplasmic poxviruses.IMPORTANCE Viral mimicry of cellular signaling modulators provides clear evidence that the pathogen targets an important host pathway during infection. Poxviruses employ numerous viral homologs of cellular proteins, the study of which have yielded insights into signaling pathways used by both virus and cells alike. The vaccinia virus B1 protein is a homolog of cellular vaccinia virus-related kinases (VRKs) and is needed for viral DNA replication and likely other stages of the viral life cycle. However, much remains to be learned about how B1 and VRKs overlap functionally. This study utilizes new tools, including a B1 deletion virus and VRK knockout cells, to further characterize the functional links between the viral and cellular enzymes. As a result, we have discovered that B1 and VRK2 target a common set of substrates vital to productive infection of this large cytoplasmic DNA virus.
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17
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Hu X, Zhu M, Liang Z, Kumar D, Chen F, Zhu L, Kuang S, Xue R, Cao G, Gong C. Proteomic analysis of BmN cell lipid rafts reveals roles in Bombyx mori nucleopolyhedrovirus infection. Mol Genet Genomics 2017; 292:465-474. [DOI: 10.1007/s00438-016-1284-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 12/26/2016] [Indexed: 11/25/2022]
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18
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Molluscum Contagiosum Virus Transcriptome in Abortively Infected Cultured Cells and a Human Skin Lesion. J Virol 2016; 90:4469-4480. [PMID: 26889040 DOI: 10.1128/jvi.02911-15] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 02/12/2016] [Indexed: 12/23/2022] Open
Abstract
UNLABELLED Molluscum contagiosum virus (MOCV), the only circulating human-specific poxvirus, has a worldwide distribution and causes benign skin lesions that may persist for months in young children and severe infections in immunosuppressed adults. Studies of MOCV are restricted by the lack of an efficient animal model or a cell culture replication system. We used next-generation sequencing to analyze and compare polyadenylated RNAs from abortive MOCV infections of several cell lines and a human skin lesion. Viral RNAs were detected for 14 days after MOCV infection of cultured cells; however, there was little change in the RNA species during this time and a similar pattern occurred in the presence of an inhibitor of protein synthesis, indicating a block preventing postreplicative gene expression. Moreover, a considerable number of MOCV RNAs mapped to homologs of orthopoxvirus early genes, but few did so to homologs of intermediate or late genes. The RNAs made during in vitro infections represent a subset of RNAs detected in human skin lesions which mapped to homologs of numerous postreplicative as well as early orthopoxvirus genes. Transfection experiments using fluorescent protein and luciferase reporters demonstrated that vaccinia virus recognized MOCV intermediate and late promoters, indicating similar gene regulation. The specific recognition of the intermediate promoter in MOCV-infected cells provided evidence for the synthesis of intermediate transcription factors, which are products of early genes, but not for late transcription factors. Transcriptome sequencing (RNA-seq) and reporter gene assays may be useful for testing engineered cell lines and conditions that ultimately could provide an in vitro replication system. IMPORTANCE The inability to propagate molluscum contagiosum virus, which causes benign skin lesions in young children and more extensive infections in immunosuppressed adults, has constrained our understanding of the biology of this human-specific virus. In the present study, we characterized the RNAs synthesized in abortively infected cultured cells and a human skin lesion by next-generation sequencing. These studies provided an initial transcription map of the MOCV genome, suggested temporal regulation of gene expression, and indicated that the in vitro replication block occurs prior to intermediate and late gene expression. RNA-seq and reporter assays, as described here, may help to further evaluate MOCV gene expression and define conditions that could enable MOCV replication in vitro.
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19
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The Barrier to Autointegration Factor: Interlocking Antiviral Defense with Genome Maintenance. J Virol 2016; 90:3806-3809. [PMID: 26842478 DOI: 10.1128/jvi.00178-16] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Intrinsic defenses targeting foreign DNA are one facet of the cellular armament tasked with protecting host genomic integrity. The DNA binding protein BAF (barrier to autointegration factor) contributes to multiple aspects of genome maintenance and intercepts retrovirus, poxvirus, and herpesvirus genomes during infection. In this gem, we discuss the unique position BAF occupies at the virus-host interface and how both viral and cellular mechanisms may regulate its capacity to act as a pro- or antiviral effector targeting viral DNA.
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20
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Vaccinia Virus B1 Kinase Is Required for Postreplicative Stages of the Viral Life Cycle in a BAF-Independent Manner in U2OS Cells. J Virol 2015. [PMID: 26223647 DOI: 10.1128/jvi.01252-15] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
UNLABELLED The vaccinia virus B1R gene encodes a highly conserved protein kinase that is essential for the poxviral life cycle. As demonstrated in many cell types, B1 plays a critical role during viral DNA replication when it inactivates the cellular host defense effector barrier to autointegration factor (BAF or BANF1). To better understand the role of B1 during infection, we have characterized the growth of a B1-deficient temperature-sensitive mutant virus (Cts2 virus) in U2OS osteosarcoma cells. In contrast to all other cell lines tested to date, we found that in U2OS cells, Cts2 viral DNA replication is unimpaired at the nonpermissive temperature. However, the Cts2 viral yield in these cells was reduced more than 10-fold, thus indicating that B1 is required at another stage of the vaccinia virus life cycle. Our results further suggest that the host defense function of endogenous BAF may be absent in U2OS cells but can be recovered through either overexpression of BAF or fusion of U2OS cells with mouse cells in which the antiviral function of BAF is active. Interestingly, examination of late viral proteins during Cts2 virus infection demonstrated that B1 is required for optimal processing of the L4 protein. Finally, execution point analyses as well as electron microscopy studies uncovered a role for B1 during maturation of poxviral virions. Overall, this work demonstrates that U2OS cells are a novel model system for studying the cell type-specific regulation of BAF and reveals a role for B1 beyond DNA replication during the late stages of the viral life cycle. IMPORTANCE The most well characterized role for the vaccinia virus B1 kinase is to facilitate viral DNA replication by phosphorylating and inactivating BAF, a cellular host defense responsive to foreign DNA. Additional roles for B1 later in the viral life cycle have been postulated for decades but are difficult to examine directly due to the importance of B1 during DNA replication. Here, we demonstrate that in U2OS cells, a B1 mutant virus escapes the block in DNA replication observed in other cell types and, instead, this mutant virus exhibits impaired late protein accumulation and incomplete maturation of new virions. These data provide the clearest evidence to date that B1 is needed for multiple critical junctures in the poxviral life cycle in a manner that is both dependent on and independent of BAF.
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21
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Jamin A, Wiebe MS. Barrier to Autointegration Factor (BANF1): interwoven roles in nuclear structure, genome integrity, innate immunity, stress responses and progeria. Curr Opin Cell Biol 2015; 34:61-8. [PMID: 26072104 DOI: 10.1016/j.ceb.2015.05.006] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Revised: 05/20/2015] [Accepted: 05/27/2015] [Indexed: 11/24/2022]
Abstract
The Barrier to Autointegration Factor (BAF or BANF1) is an abundant, highly conserved DNA binding protein. BAF is involved in multiple pathways including mitosis, nuclear assembly, viral infection, chromatin and gene regulation and the DNA damage response. BAF is also essential for early development in metazoans and relevant to human physiology; BANF1 mutations cause a progeroid syndrome, placing BAF within the laminopathy disease spectrum. This review summarizes previous knowledge about BAF in the context of recent discoveries about its protein partners, posttranslational regulation, dynamic subcellular localizations and roles in disease, innate immunity, transposable elements and genome integrity.
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Affiliation(s)
- Augusta Jamin
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska, Lincoln, NE 68583-0900, USA; Nebraska Center for Virology, University of Nebraska, Lincoln, NE 68583-0900, USA
| | - Matthew S Wiebe
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska, Lincoln, NE 68583-0900, USA; Nebraska Center for Virology, University of Nebraska, Lincoln, NE 68583-0900, USA.
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22
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Jamin A, Thunuguntla P, Wicklund A, Jones C, Wiebe MS. Barrier to auto integration factor becomes dephosphorylated during HSV-1 Infection and Can Act as a host defense by impairing viral DNA replication and gene expression. PLoS One 2014; 9:e100511. [PMID: 24945635 PMCID: PMC4063967 DOI: 10.1371/journal.pone.0100511] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Accepted: 05/28/2014] [Indexed: 12/28/2022] Open
Abstract
BAF (Barrier to Autointegration Factor) is a highly conserved DNA binding protein that senses poxviral DNA in the cytoplasm and tightly binds to the viral genome to interfere with DNA replication and transcription. To counteract BAF, a poxviral-encoded protein kinase phosphorylates BAF, which renders BAF unable to bind DNA and allows efficient viral replication to occur. Herein, we examined how BAF phosphorylation is affected by herpes simplex virus type 1 (HSV-1) infection and tested the ability of BAF to interfere with HSV-1 productive infection. Interestingly, we found that BAF phosphorylation decreases markedly following HSV-1 infection. To determine whether dephosphorylated BAF impacts HSV-1 productive infection, we employed cell lines stably expressing a constitutively unphosphorylated form of BAF (BAF-MAAAQ) and cells overexpressing wild type (wt) BAF for comparison. Although HSV-1 production in cells overexpressing wtBAF was similar to that in cells expressing no additional BAF, viral growth was reduced approximately 80% in the presence of BAF-MAAAQ. Experiments were also performed to determine the mechanism of the antiviral activity of BAF with the following results. BAF-MAAAQ was localized to the nucleus, whereas wtBAF was dispersed throughout cells prior to infection. Following infection, wtBAF becomes dephosphorylated and relocalized to the nucleus. Additionally, BAF was associated with the HSV-1 genome during infection, with BAF-MAAAQ associated to a greater extent than wtBAF. Importantly, unphosphorylated BAF inhibited both viral DNA replication and gene expression. For example, expression of two regulatory proteins, ICP0 and VP16, were substantially reduced in cells expressing BAF-MAAAQ. However, other viral genes were not dramatically affected suggesting that expression of certain viral genes can be differentially regulated by unphosphorylated BAF. Collectively, these results suggest that BAF can act in a phosphorylation-regulated manner to impair HSV-1 transcription and/or DNA replication, which is similar to the antiviral activity of BAF during vaccinia infection.
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Affiliation(s)
- Augusta Jamin
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska, Lincoln, Nebraska, United States of America
- Nebraska Center for Virology, University of Nebraska, Lincoln, Nebraska, United States of America
| | - Prasanth Thunuguntla
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska, Lincoln, Nebraska, United States of America
- Nebraska Center for Virology, University of Nebraska, Lincoln, Nebraska, United States of America
| | - April Wicklund
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska, Lincoln, Nebraska, United States of America
- Nebraska Center for Virology, University of Nebraska, Lincoln, Nebraska, United States of America
| | - Clinton Jones
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska, Lincoln, Nebraska, United States of America
- Nebraska Center for Virology, University of Nebraska, Lincoln, Nebraska, United States of America
| | - Matthew S. Wiebe
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska, Lincoln, Nebraska, United States of America
- Nebraska Center for Virology, University of Nebraska, Lincoln, Nebraska, United States of America
- * E-mail:
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23
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Cell- and virus-mediated regulation of the barrier-to-autointegration factor's phosphorylation state controls its DNA binding, dimerization, subcellular localization, and antipoxviral activity. J Virol 2014; 88:5342-55. [PMID: 24600006 DOI: 10.1128/jvi.00427-14] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
UNLABELLED Barrier-to-autointegration factor (BAF) is a DNA binding protein with multiple cellular functions, including the ability to act as a potent defense against vaccinia virus infection. This antiviral function involves BAF's ability to condense double-stranded DNA and subsequently prevent viral DNA replication. In recent years, it has become increasingly evident that dynamic phosphorylation involving the vaccinia virus B1 kinase and cellular enzymes is likely a key regulator of multiple BAF functions; however, the precise mechanisms are poorly understood. Here we analyzed how phosphorylation impacts BAF's DNA binding, subcellular localization, dimerization, and antipoxviral activity through the characterization of BAF phosphomimetic and unphosphorylatable mutants. Our studies demonstrate that increased phosphorylation enhances BAF's mobilization from the nucleus to the cytosol, while dephosphorylation restricts BAF to the nucleus. Phosphorylation also impairs both BAF's dimerization and its DNA binding activity. Furthermore, our studies of BAF's antiviral activity revealed that hyperphosphorylated BAF is unable to suppress viral DNA replication or virus production. Interestingly, the unphosphorylatable BAF mutant, which is capable of binding DNA but localizes predominantly to the nucleus, was also incapable of suppressing viral replication. Thus, both DNA binding and localization are important determinants of BAF's antiviral function. Finally, our examination of how phosphatases are involved in regulating BAF revealed that PP2A dephosphorylates BAF during vaccinia infection, thus counterbalancing the activity of the B1 kinase. Altogether, these data demonstrate that phosphoregulation of BAF by viral and cellular enzymes modulates this protein at multiple molecular levels, thus determining its effectiveness as an antiviral factor and likely other functions as well. IMPORTANCE The barrier-to-autointegration factor (BAF) contributes to cellular genomic integrity in multiple ways, the best characterized of which are as a host defense against cytoplasmic DNA and as a regulator of mitotic nuclear reassembly. Although dynamic phosphorylation involving both viral and cellular enzymes is likely a key regulator of multiple BAF functions, the precise mechanisms involved are poorly understood. Here we demonstrate that phosphorylation coordinately regulates BAF's DNA binding, subcellular localization, dimerization, and antipoxviral activity. Overall, our findings provide new insights into how phosphoregulation of BAF modulates this protein at multiple levels and governs its effectiveness as an antiviral factor against foreign DNA.
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24
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Matson J, Chou W, Ngo T, Gershon PD. Static and dynamic protein phosphorylation in the Vaccinia virion. Virology 2014; 452-453:310-23. [PMID: 24606709 DOI: 10.1016/j.virol.2014.01.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 12/02/2013] [Accepted: 01/17/2014] [Indexed: 11/19/2022]
Abstract
To the best of our knowledge, two phosphorylation sites have been reported previously, among 11 known Vaccinia virus phosphoproteins. Here, via phosphopeptide mass spectrometry, up to 189 phosphorylation sites were identified among 48 proteins in preparations of purified Vaccinia mature virus (MV). 8.5% of phospho-residues were pTyr. Viral phosphoproteins were found in diverse functional classes, including structural proteins, membrane proteins and RNA polymerase subunits. Among the nine identified membrane phosphoproteins, the sites in just one, namely A14L, were deduced to be internal with respect to the accompanying membrane. Examination of sites in known substrates of the Vaccinia-encoded protein kinase VPK2, indicated VPK2 to be a proline-dependent kinase. The MV phosphoproteome was enriched in potential substrates of cellular kinases belonging to the CDK2/CDK3, CK2, and p38 groups. Quantitative mass spectrometry identified several sites that became phosphorylated during intravirion kinase activation in vitro, each showing one of two distinct pH-dependency profiles.
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Affiliation(s)
- J Matson
- University of North Carolina, Chapel Hill, NC, United States
| | - W Chou
- Department of Molecular Biology and Biochemistry, UC-Irvine, Irvine, CA 92697, United States
| | - T Ngo
- Department of Molecular Biology and Biochemistry, UC-Irvine, Irvine, CA 92697, United States
| | - P D Gershon
- Department of Molecular Biology and Biochemistry, UC-Irvine, Irvine, CA 92697, United States.
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