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Ma Z, Hao J, Yang Z, Zhang M, Xin J, Bi H, Guo D. Research Progress on the Role of Ubiquitination in Eye Diseases. Cell Biochem Biophys 2024:10.1007/s12013-024-01381-y. [PMID: 38913283 DOI: 10.1007/s12013-024-01381-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/19/2024] [Indexed: 06/25/2024]
Abstract
The occurrence and development of ophthalmic diseases are related to the dysfunction of eye tissues. Ubiquitin is an important form of protein post-translational modification, which plays an essential role in the occurrence and development of diseases through specific modification of target proteins. Ubiquitination governs a variety of intracellular signal transduction processes, including proteasome degradation, DNA damage repair, and cell cycle progression. Studies have found that ubiquitin can play a role in eye diseases such as cataracts, glaucoma, keratopathy, retinopathy, and eye tumors. In this paper, the role of protein ubiquitination in eye diseases was reviewed.
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Affiliation(s)
- Zhongyu Ma
- Shandong University of Traditional Chinese Medicine, Jinan, 250002, China
| | - Jiawen Hao
- Shandong University of Traditional Chinese Medicine, Jinan, 250002, China
| | - Zhaohui Yang
- Shandong University of Traditional Chinese Medicine, Jinan, 250002, China
| | - Miao Zhang
- Shandong University of Traditional Chinese Medicine, Jinan, 250002, China
| | - Jizhao Xin
- Shandong University of Traditional Chinese Medicine, Jinan, 250002, China
| | - Hongsheng Bi
- Affiliated Eye Hospital of Shandong University of Traditional Chinese Medicine, Jinan, 250002, China.
- Shandong Provincial Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Therapy of Ocular Diseases, Shandong Academy of Eye Disease Prevention and Therapy, Shandong Provincial Clinical Research Center of Ophthalmology and Children Visual Impairment Prevention and Control, Shandong Engineering Technology Research Center of Visual Intelligence, Shandong Academy of Health and Myopia Prevention and Control of Children and Adolescents, Jinan, 250002, China.
- Medical College of Optometry and Ophthalmology, Shandong University of Traditional Chinese Medicine, Jinan, 250002, China.
| | - Dadong Guo
- Affiliated Eye Hospital of Shandong University of Traditional Chinese Medicine, Jinan, 250002, China.
- Shandong Provincial Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Therapy of Ocular Diseases, Shandong Academy of Eye Disease Prevention and Therapy, Shandong Provincial Clinical Research Center of Ophthalmology and Children Visual Impairment Prevention and Control, Shandong Engineering Technology Research Center of Visual Intelligence, Shandong Academy of Health and Myopia Prevention and Control of Children and Adolescents, Jinan, 250002, China.
- Medical College of Optometry and Ophthalmology, Shandong University of Traditional Chinese Medicine, Jinan, 250002, China.
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Zegeye Y, Aredo B, Yuksel S, Kirman DC, Kumar A, Chen B, Turpin E, Shresta S, He YG, Gautron L, Tang M, Li X, DiCesare SM, Hulleman JD, Xing C, Ludwig S, Moresco EMY, Beutler BA, Ufret-Vincenty RL. E3 ubiquitin ligase Herc3 deficiency leads to accumulation of subretinal microglia and retinal neurodegeneration. Sci Rep 2024; 14:3010. [PMID: 38321224 PMCID: PMC10847449 DOI: 10.1038/s41598-024-53731-8] [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: 08/01/2023] [Accepted: 02/04/2024] [Indexed: 02/08/2024] Open
Abstract
Activated microglia have been implicated in the pathogenesis of age-related macular degeneration (AMD), diabetic retinopathy, and other neurodegenerative and neuroinflammatory disorders, but our understanding of the mechanisms behind their activation is in infant stages. With the goal of identifying novel genes associated with microglial activation in the retina, we applied a semiquantitative fundus spot scoring scale to an unbiased, state-of-the-science mouse forward genetics pipeline. A mutation in the gene encoding the E3 ubiquitin ligase Herc3 led to prominent accumulation of fundus spots. CRISPR mutagenesis was used to generate Herc3-/- mice, which developed prominent accumulation of fundus spots and corresponding activated Iba1 + /CD16 + subretinal microglia, retinal thinning on OCT and histology, and functional deficits by Optomotory and electrophysiology. Bulk RNA sequencing identified activation of inflammatory pathways and differentially expressed genes involved in the modulation of microglial activation. Thus, despite the known expression of multiple E3 ubiquitin ligases in the retina, we identified a non-redundant role for Herc3 in retinal homeostasis. Our findings are significant given that a dysregulated ubiquitin-proteasome system (UPS) is important in prevalent retinal diseases, in which activated microglia appear to play a role. This association between Herc3 deficiency, retinal microglial activation and retinal degeneration merits further study.
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Affiliation(s)
- Yeshumenesh Zegeye
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Bogale Aredo
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Seher Yuksel
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Dogan Can Kirman
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Ashwani Kumar
- McDermott Center for Human Growth and Development, UT Southwestern Medical Center, Dallas, TX, USA
| | - Bo Chen
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, USA
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Emily Turpin
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Sangita Shresta
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Yu-Guang He
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Laurent Gautron
- Center for Hypothalamic Research and Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Miao Tang
- Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Xiaohong Li
- Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Sophia M DiCesare
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, USA
| | - John D Hulleman
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Chao Xing
- McDermott Center for Human Growth and Development, UT Southwestern Medical Center, Dallas, TX, USA
- Department of Bioinformatics, UT Southwestern Medical Center, Dallas, TX, USA
| | - Sara Ludwig
- Center for Hypothalamic Research and Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Eva Marie Y Moresco
- Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Bruce A Beutler
- Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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El-Saafin F, Devys D, Johnsen SA, Vincent SD, Tora L. SAGA-Dependent Histone H2Bub1 Deubiquitination Is Essential for Cellular Ubiquitin Balance during Embryonic Development. Int J Mol Sci 2022; 23:ijms23137459. [PMID: 35806465 PMCID: PMC9267394 DOI: 10.3390/ijms23137459] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Revised: 06/30/2022] [Accepted: 06/30/2022] [Indexed: 12/24/2022] Open
Abstract
Ubiquitin (ub) is a small, highly conserved protein widely expressed in eukaryotic cells. Ubiquitination is a post-translational modification catalyzed by enzymes that activate, conjugate, and ligate ub to proteins. Substrates can be modified either by addition of a single ubiquitin molecule (monoubiquitination), or by conjugation of several ubs (polyubiquitination). Monoubiquitination acts as a signaling mark to control diverse biological processes. The cellular and spatial distribution of ub is determined by the opposing activities of ub ligase enzymes, and deubiquitinases (DUBs), which remove ub from proteins to generate free ub. In mammalian cells, 1–2% of total histone H2B is monoubiquitinated. The SAGA (Spt Ada Gcn5 Acetyl-transferase) is a transcriptional coactivator and its DUB module removes ub from H2Bub1. The mammalian SAGA DUB module has four subunits, ATXN7, ATXN7L3, USP22, and ENY2. Atxn7l3−/− mouse embryos, lacking DUB activity, have a five-fold increase in H2Bub1 retention, and die at mid-gestation. Interestingly, embryos lacking the ub encoding gene, Ubc, have a similar phenotype. Here we provide a current overview of data suggesting that H2Bub1 retention on the chromatin in Atxn7l3−/− embryos may lead to an imbalance in free ub distribution. Thus, we speculate that ATXN7L3-containing DUBs impact the free cellular ub pool during development.
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Affiliation(s)
- Farrah El-Saafin
- Olivia Newton-John Cancer Research Institute, Melbourne 3095, Australia;
| | - Didier Devys
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, 67404 Illkirch, France;
- Centre National de la Recherche Scientifique (CNRS), UMR7104, 67404 Illkirch, France
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1258, 67404 Illkirch, France
- Université de Strasbourg, 67404 Illkirch, France
| | | | - Stéphane D. Vincent
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, 67404 Illkirch, France;
- Centre National de la Recherche Scientifique (CNRS), UMR7104, 67404 Illkirch, France
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1258, 67404 Illkirch, France
- Université de Strasbourg, 67404 Illkirch, France
- Correspondence: (S.D.V.); (L.T.); Tel.: +33-3-88653425 (S.D.V.); +33-3-88653444 (L.T.)
| | - László Tora
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, 67404 Illkirch, France;
- Centre National de la Recherche Scientifique (CNRS), UMR7104, 67404 Illkirch, France
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1258, 67404 Illkirch, France
- Université de Strasbourg, 67404 Illkirch, France
- Correspondence: (S.D.V.); (L.T.); Tel.: +33-3-88653425 (S.D.V.); +33-3-88653444 (L.T.)
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Shen WY, Fu XH, Cai J, Li WC, Fan BY, Pang YL, Zhao CX, Abula M, Kong XH, Yao X, Feng SQ. Identification of key genes involved in recovery from spinal cord injury in adult zebrafish. Neural Regen Res 2021; 17:1334-1342. [PMID: 34782579 PMCID: PMC8643032 DOI: 10.4103/1673-5374.327360] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Zebrafish are an effective vertebrate model to study the mechanisms underlying recovery after spinal cord injury. The subacute phase after spinal cord injury is critical to the recovery of neurological function, which involves tissue bridging and axon regeneration. In this study, we found that zebrafish spontaneously recovered 44% of their swimming ability within the subacute phase (2 weeks) after spinal cord injury. During this period, we identified 7762 differentially expressed genes in spinal cord tissue: 2950 were up-regulated and 4812 were down-regulated. These differentially expressed genes were primarily concentrated in the biological processes of the respiratory chain, axon regeneration, and cell-component morphogenesis. The genes were also mostly involved in the regulation of metabolic pathways, the cell cycle, and gene-regulation pathways. We verified the gene expression of two differentially expressed genes, clasp2 up-regulation and h1m down-regulation, in zebrafish spinal cord tissue in vitro. Pathway enrichment analysis revealed that up-regulated clasp2 functions similarly to microtubule-associated protein, which is responsible for axon extension regulated by microtubules. Down-regulated h1m controls endogenous stem cell differentiation after spinal cord injury. This study provides new candidate genes, clasp2 and h1m, as potential therapeutic intervention targets for spinal cord injury repair by neuroregeneration. All experimental procedures and protocols were approved by the Animal Ethics Committee of Tianjin Institute of Medical & Pharmaceutical Sciences (approval No. IMPS-EAEP-Q-2019-02) on September 24, 2019.
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Affiliation(s)
- Wen-Yuan Shen
- International Science and Technology Cooperation Base of Spinal Cord Injury, Tianjin Key Laboratory of Spine and Spinal Cord, Department of Orthopedics, Tianjin Medical University General Hospital, Tianjin, China
| | - Xuan-Hao Fu
- International Science and Technology Cooperation Base of Spinal Cord Injury, Tianjin Key Laboratory of Spine and Spinal Cord, Department of Orthopedics, Tianjin Medical University General Hospital, Tianjin, China
| | - Jun Cai
- Tianjin Medicine and Health Research Center, Tianjin Institute of Medical & Pharmaceutical Sciences, Tianjin, China
| | - Wen-Chang Li
- Tianjin Medicine and Health Research Center, Tianjin Institute of Medical & Pharmaceutical Sciences, Tianjin, China
| | - Bao-You Fan
- International Science and Technology Cooperation Base of Spinal Cord Injury, Tianjin Key Laboratory of Spine and Spinal Cord, Department of Orthopedics, Tianjin Medical University General Hospital, Tianjin, China
| | - Yi-Lin Pang
- International Science and Technology Cooperation Base of Spinal Cord Injury, Tianjin Key Laboratory of Spine and Spinal Cord, Department of Orthopedics, Tianjin Medical University General Hospital, Tianjin, China
| | - Chen-Xi Zhao
- International Science and Technology Cooperation Base of Spinal Cord Injury, Tianjin Key Laboratory of Spine and Spinal Cord, Department of Orthopedics, Tianjin Medical University General Hospital, Tianjin, China
| | - Muhtidir Abula
- International Science and Technology Cooperation Base of Spinal Cord Injury, Tianjin Key Laboratory of Spine and Spinal Cord, Department of Orthopedics, Tianjin Medical University General Hospital, Tianjin, China
| | | | - Xue Yao
- International Science and Technology Cooperation Base of Spinal Cord Injury, Tianjin Key Laboratory of Spine and Spinal Cord, Department of Orthopedics, Tianjin Medical University General Hospital, Tianjin, China
| | - Shi-Qing Feng
- International Science and Technology Cooperation Base of Spinal Cord Injury, Tianjin Key Laboratory of Spine and Spinal Cord, Department of Orthopedics, Tianjin Medical University General Hospital, Tianjin, China
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Park CW, Bae JS, Ryu KY. Simultaneous Disruption of Both Polyubiquitin Genes Affects Proteasome Function and Decreases Cellular Proliferation. Cell Biochem Biophys 2020; 78:321-329. [PMID: 32705536 DOI: 10.1007/s12013-020-00933-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 07/13/2020] [Indexed: 12/26/2022]
Abstract
The ubiquitin (Ub) proteasome system is important for maintaining protein homeostasis and has various roles in cell signaling, proliferation, and cell cycle regulation. In mammals, Ub is encoded by two monoubiquitin and two polyubiquitin genes. Although reduced levels of Ub due to the disruption of one polyubiquitin gene are known to decrease cell proliferation, the effect of disrupting both polyubiquitin genes remains elusive. Polyubiquitin gene Ubc knockout mice are embryonically lethal and polyubiquitin gene Ubb knockout mice are infertile. Thus, it is difficult to study the effects of double knockouts (DKOs). In the present study, the CRISPR/Cas9 system was used to simultaneously knockout both polyubiquitin genes, UBB and UBC, in HEK293T and HeLa cells. In DKO cells, growth decreased significantly compared to the control cells. We observed reduced proteasome function and reduced levels of free Ub in DKO cells. However, the levels of purified proteasome were not different between control and DKO cells, although the mRNA levels of proteasomal subunits were significantly increased in latter. We propose that the reduction of Ub levels, by disruption of both polyubiquitin genes, resulted in an altered proteasomal status, leading to the reduced proteasome activity, and decreased cellular proliferation.
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Affiliation(s)
- Chul-Woo Park
- Department of Life Science, University of Seoul, Seoul, 02504, Republic of Korea
| | - Jin-Sil Bae
- Department of Life Science, University of Seoul, Seoul, 02504, Republic of Korea
| | - Kwon-Yul Ryu
- Department of Life Science, University of Seoul, Seoul, 02504, Republic of Korea.
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Park CW, Jung BK, Ryu KY. Disruption of the polyubiquitin gene Ubb reduces the self-renewal capacity of neural stem cells. Biochem Biophys Res Commun 2020; 527:372-378. [PMID: 32321641 DOI: 10.1016/j.bbrc.2020.04.042] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 04/10/2020] [Indexed: 02/08/2023]
Abstract
Ubiquitin (Ub) is a highly conserved eukaryotic protein that plays pivotal roles in cellular signal transduction, differentiation, and proteolysis. Although we have previously reported that disruption of the polyubiquitin gene Ubb is associated with the dysregulated differentiation of neural stem cells (NSCs) into neurons, it is unclear how gene expression patterns are altered in Ubb knockout (KO) NSCs, and whether this altered gene expression contributes to Ubb KO neural phenotypes. To answer these questions, we used RNA-Seq to compare the transcriptomes of Ubb KO NSCs and Ubb heterozygous (HT) controls. We found that the expression levels of most proliferation markers were decreased in Ubb KO NSCs. To determine whether the reduced levels of proliferation markers were due to reduced self-renewal of NSCs, such as radial glia, we measured the levels of the radial glia marker, Pax6, in mouse embryonic brains at 14.5 dpc. We found that Pax6 levels were decreased and the ventricular zone was thinner in the embryonic brains of Ubb KO mice compared to those of wild-type (WT) control mice. To determine whether the decreased self-renewal of Ubb KO NSCs was caused by cell-autonomous defects and not due to their microenvironment, we transplanted NSCs into WT mouse brains using a cannula system. In mouse brain sections, immunoreactivity of the NSC marker, nestin, was much lower in Ubb KO NSCs than in Ubb HT controls. Therefore, our data suggest that cell-autonomous defects, due to the disruption of Ubb, lead to a decrease in the self-renewal capacity of NSCs and may contribute to their dysregulated differentiation into neurons.
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Affiliation(s)
- Chul-Woo Park
- Department of Life Science, University of Seoul, Seoul, 02504, Republic of Korea
| | - Byung-Kwon Jung
- Department of Life Science, University of Seoul, Seoul, 02504, Republic of Korea
| | - Kwon-Yul Ryu
- Department of Life Science, University of Seoul, Seoul, 02504, Republic of Korea.
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Collin GB, Gogna N, Chang B, Damkham N, Pinkney J, Hyde LF, Stone L, Naggert JK, Nishina PM, Krebs MP. Mouse Models of Inherited Retinal Degeneration with Photoreceptor Cell Loss. Cells 2020; 9:cells9040931. [PMID: 32290105 PMCID: PMC7227028 DOI: 10.3390/cells9040931] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 04/05/2020] [Accepted: 04/07/2020] [Indexed: 12/12/2022] Open
Abstract
Inherited retinal degeneration (RD) leads to the impairment or loss of vision in millions of individuals worldwide, most frequently due to the loss of photoreceptor (PR) cells. Animal models, particularly the laboratory mouse, have been used to understand the pathogenic mechanisms that underlie PR cell loss and to explore therapies that may prevent, delay, or reverse RD. Here, we reviewed entries in the Mouse Genome Informatics and PubMed databases to compile a comprehensive list of monogenic mouse models in which PR cell loss is demonstrated. The progression of PR cell loss with postnatal age was documented in mutant alleles of genes grouped by biological function. As anticipated, a wide range in the onset and rate of cell loss was observed among the reported models. The analysis underscored relationships between RD genes and ciliary function, transcription-coupled DNA damage repair, and cellular chloride homeostasis. Comparing the mouse gene list to human RD genes identified in the RetNet database revealed that mouse models are available for 40% of the known human diseases, suggesting opportunities for future research. This work may provide insight into the molecular players and pathways through which PR degenerative disease occurs and may be useful for planning translational studies.
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Affiliation(s)
- Gayle B. Collin
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Navdeep Gogna
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Bo Chang
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Nattaya Damkham
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
- Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
- Siriraj Center of Excellence for Stem Cell Research, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
| | - Jai Pinkney
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Lillian F. Hyde
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Lisa Stone
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Jürgen K. Naggert
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Patsy M. Nishina
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
- Correspondence: (P.M.N.); (M.P.K.); Tel.: +1-207-2886-383 (P.M.N.); +1-207-2886-000 (M.P.K.)
| | - Mark P. Krebs
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
- Correspondence: (P.M.N.); (M.P.K.); Tel.: +1-207-2886-383 (P.M.N.); +1-207-2886-000 (M.P.K.)
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A negative feedback mechanism links UBC gene expression to ubiquitin levels by affecting RNA splicing rather than transcription. Sci Rep 2019; 9:18556. [PMID: 31811203 PMCID: PMC6898720 DOI: 10.1038/s41598-019-54973-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 11/20/2019] [Indexed: 12/16/2022] Open
Abstract
UBC gene plays a critical role in maintaining ubiquitin (Ub) homeostasis. It is upregulated under stress conditions, and herein we report that it is downregulated upon Ub overexpression. Downregulation occurs in a dose-dependent manner, suggesting the existence of a fine-tuned Ub sensing mechanism. This “sensor” requires a conjugation competent ubiquitin to detect Ub levels. Searching the sensor among the transcription factors involved in basal and stress-induced UBC gene expression was unsuccessful. Neither HSF1 and HSF2, nor Sp1 and YY1 are affected by the increased Ub levels. Moreover, mutagenesis of their binding sites in the UBC promoter-driven reporter constructs does not impair the downmodulation effect. Epigenetic studies show that H2A and H2B ubiquitination within the UBC promoter region is unchanged upon ubiquitin overexpression. Noteworthy, quantification of nascent RNA molecules excludes that the downmodulation arises in the transcription initiation step, rather pointing towards a post-transcriptional mechanism. Indeed, a significantly higher fraction of unspliced UBC mRNA is detected in ubiquitin overexpressing cells, compared to empty vector transfected cells. Our findings suggest how increasing cellular ubiquitin levels may control the expression of UBC gene by negatively affecting the splicing of its pre-mRNA, providing a straightforward feedback strategy for the homeostatic control of ubiquitin pools.
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