KSHV Activates Unfolded Protein Response Sensors but Suppresses Downstream Transcriptional Responses to Support Lytic Replication
| العنوان: | KSHV Activates Unfolded Protein Response Sensors but Suppresses Downstream Transcriptional Responses to Support Lytic Replication |
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| المؤلفون: | Benjamin P. Johnston, Eric S. Pringle, Craig McCormick |
| المصدر: | Proceedings, Vol 50, Iss 116, p 116 (2020) PLoS Pathogens, Vol 15, Iss 12, p e1008185 (2019) PLoS Pathogens |
| بيانات النشر: | MDPI AG, 2020. |
| سنة النشر: | 2020 |
| مصطلحات موضوعية: | 0209 industrial biotechnology, viruses, Gene Expression, 02 engineering and technology, Virus Replication, Pathology and Laboratory Medicine, Endoplasmic Reticulum, 01 natural sciences, Biochemistry, Virions, 020901 industrial engineering & automation, Medicine and Health Sciences, Post-Translational Modification, Phosphorylation, Biology (General), ATF6, 0303 health sciences, Secretory Pathway, Messenger RNA, 030302 biochemistry & molecular biology, Herpesviridae Infections, Kaposi's Sarcoma-Associated Herpesvirus, unfolded protein response, Endoplasmic Reticulum Stress, Cell biology, Virus Latency, Nucleic acids, Lytic cycle, Medical Microbiology, Cell Processes, Viral Pathogens, Herpesvirus 8, Human, Viruses, Pathogens, Cellular Structures and Organelles, Research Article, PERK, Herpesviruses, XBP1, QH301-705.5, Immunology, DNA transcription, lcsh:A, KSHV, IRE1, Biology, Viral Structure, Microbiology, Cell Line, 03 medical and health sciences, Virology, DNA-binding proteins, Genetics, Humans, Gene Regulation, Molecular Biology, Transcription factor, Microbial Pathogens, 030304 developmental biology, lytic, 010401 analytical chemistry, ATF4, Organisms, Biology and Life Sciences, Proteins, Cell Biology, biochemical phenomena, metabolism, and nutrition, RC581-607, Viral Replication, 0104 chemical sciences, Regulatory Proteins, Viral replication, Unfolded protein response, RNA, Parasitology, Ectopic expression, Virus Activation, Immunologic diseases. Allergy, lcsh:General Works, DNA viruses, Transcription Factors |
| الوصف: | Herpesviruses usurp host cell protein synthesis machinery to convert viral mRNAs into proteins, and the endoplasmic reticulum (ER) to ensure proper folding, post-translational modification and trafficking of secreted and transmembrane viral proteins. Overloading ER folding capacity activates the unfolded protein response (UPR), whereby sensor proteins ATF6, PERK and IRE1 initiate a stress-mitigating transcription program that accelerates catabolism of misfolded proteins while increasing ER folding capacity. Kaposi’s sarcoma-associated herpesvirus (KSHV) can be reactivated from latency by chemical induction of ER stress, which causes accumulation of the XBP1s transcription factor that transactivates the viral RTA lytic switch gene. The presence of XBP1s-responsive elements in the RTA promoter suggests that KSHV evolved a mechanism to respond to ER stress. Here, we report that ATF6, PERK and IRE1 were activated upon reactivation from latency and required for efficient KSHV lytic replication; genetic or pharmacologic inhibition of each UPR sensor diminished virion production. Despite UPR sensor activation during KSHV lytic replication, downstream UPR transcriptional responses were restricted; 1) ATF6 was cleaved to activate the ATF6(N) transcription factor but ATF6(N)-responsive genes were not transcribed; 2) PERK phosphorylated eIF2α but ATF4 did not accumulate; 3) IRE1 caused XBP1 mRNA splicing, but XBP1s protein did not accumulate and XBP1s-responsive genes were not transcribed. Ectopic expression of the KSHV host shutoff protein SOX did not affect UPR gene expression, suggesting that alternative viral mechanisms likely mediate UPR suppression during lytic replication. Complementation of XBP1s deficiency during KSHV lytic replication inhibited virion production in a dose-dependent manner in iSLK.219 cells but not in TREx-BCBL1-RTA cells. However, genetically distinct KSHV virions harvested from these two cell lines were equally susceptible to XBP1s restriction following infection of naïve iSLK cells. This suggests that cell-intrinsic properties of BCBL1 cells may circumvent the antiviral effect of ectopic XBP1s expression. Taken together, these findings indicate that while XBP1s plays an important role in reactivation from latency, it can inhibit virus replication at a later step, which the virus overcomes by preventing its synthesis. These findings suggest that KSHV hijacks UPR sensors to promote efficient viral replication while sustaining ER stress. Author summary Like all viruses, Kaposi’s sarcoma-associated herpesvirus (KSHV) uses cellular machinery to create viral proteins. Some of these proteins are folded and modified in the endoplasmic reticulum (ER) and traverse the cellular secretory apparatus. Exceeding ER protein folding capacity activates the unfolded protein response (UPR), which resolves ER stress by putting the brakes on protein synthesis and turning on stress-mitigating genes. We show that KSHV replication activates the three cellular proteins that sense ER stress, which are each required to support efficient viral replication. By contrast, KSHV blocks the UPR gene expression program downstream from each of these activated sensor proteins. The failure to resolve ER stress might normally be expected to put the virus at a disadvantage, but we demonstrate that reversal of this scenario is worse; when we supplement infected epithelial cells with the UPR transcription factor XBP1s to artificially stimulate the production of UPR-responsive gene products, virus replication is blocked at a late stage and very few viruses are released from infected cells. Taken together, these observations suggest that KSHV requires UPR sensor protein activation to replicate but has dramatically altered the outcome to prevent the synthesis of new UPR proteins and sustain stress in the ER compartment. |
| اللغة: | English |
| تدمد: | 2504-3900 |
| الوصول الحر: | https://explore.openaire.eu/search/publication?articleId=doi_dedup___::881cb569c57ca5de5926a4893a8bbe35Test https://www.mdpi.com/2504-3900/50/1/116Test |
| حقوق: | OPEN |
| رقم الانضمام: | edsair.doi.dedup.....881cb569c57ca5de5926a4893a8bbe35 |
| قاعدة البيانات: | OpenAIRE |
| تدمد: | 25043900 |
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