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Zhang B, Wang Z, Zhang S, Zhong S, Sun Y, Liu X. N6-methyloxyadenine-mediated detoxification and ferroptosis confer a trade-off between multi-fungicide resistance and fitness. mBio 2024; 15:e0317723. [PMID: 38294217 PMCID: PMC10936191 DOI: 10.1128/mbio.03177-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2023] [Accepted: 12/14/2023] [Indexed: 02/01/2024] Open
Abstract
Multi-fungicide resistance (MFR) is a serious environmental problem, which results in the excessive use of fungicides. Fitness penalty, as a common phenomenon in MFR, can partially counteract the issue of resistance due to the weakened vigor of MFR pathogens. Their underlying mechanism and relationship remain unexplained. By Oxford Nanopore Technologies sequencing and dot blot, we found that N6-methyloxyadenine (6mA) modification, the dominate epigenetic marker in Phytophthora capsici, was significantly altered after MFR emerged. Among the differently methylated genes, PcGSTZ1 could efficiently detoxify SYP-14288, a novel uncoupler, through complexing the fungicide with glutathione and induce MFR. Interestingly, PcGSTZ1 overexpression was induced by elevated 6mA levels and chromatin accessibility to its genomic loci. Moreover, the overexpression led to reactive oxygen species burst and ferroptosis in SYP-14288-resistant mutants, which enhanced the resistance and induced fitness penalty in P. capsici through triggering low energy shock adaptive response. Furthermore, this study revealed that the 6mA-PcGSTZ1-ferroptosis axis could mediate intergenerational resistance memory transmission and enabled adaptive advantage to P. capsici. In conclusion, the findings provide new insights into the biological role of 6mA as well as the mechanisms underlying the trade-off between MFR and fitness. These could also benefit disease control through the blockade of the epigenetic axis to resensitize resistant isolates.IMPORTANCEN6-methyloxyadenine (6mA) modification on DNA is correlated with tolerance under different stress in prokaryotes. However, the role of 6mA in eukaryotes remains poorly understood. Our current study reveals that DNA adenine methyltransferase 1 (DAMT1)-mediated 6mA modification at the upstream region of GST zeta 1 (GSTZ1) is elevated in the resistant strain. This elevation promotes the detoxification uncoupler and induces multifungicide resistance (MFR). Moreover, the overexpression led to reactive oxygen species burst and ferroptosis in SYP-14288-resistant mutants, which enhanced the resistance and induced fitness penalty in Phytophthora capsici through triggering low energy shock adaptive response. Furthermore, this study revealed that the 6mA-PcGSTZ1-ferroptosis axis could mediate intergenerational resistance memory transmission and enabled adaptive advantage to P. capsici. Overall, our findings uncover an innovative mechanism underlying 6mA modification in regulating PcGSTZ1 transcription and the ferroptosis pathway in P. capsici.
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Affiliation(s)
- Borui Zhang
- China Agricultural University, Beijing, China
| | - Zhiwen Wang
- China Agricultural University, Beijing, China
- Sanya Institute of China Agricultural University, Sanya, China
| | | | - Shan Zhong
- China Agricultural University, Beijing, China
| | - Ye Sun
- China Agricultural University, Beijing, China
| | - Xili Liu
- China Agricultural University, Beijing, China
- State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, China
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Sommese L, Zullo A, Mancini FP, Fabbricini R, Soricelli A, Napoli C. Clinical relevance of epigenetics in the onset and management of type 2 diabetes mellitus. Epigenetics 2017; 12:401-415. [PMID: 28059593 DOI: 10.1080/15592294.2016.1278097] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Epigenetics is involved in the altered expression of gene networks that underlie insulin resistance and insufficiency. Major genes controlling β-cell differentiation and function, such as PAX4, PDX1, and GLP1 receptor, are epigenetically controlled. Epigenetics can cause insulin resistance through immunomediated pro-inflammatory actions related to several factors, such as NF-kB, osteopontin, and Toll-like receptors. Hereafter, we provide a critical and comprehensive summary on this topic with a particular emphasis on translational and clinical aspects. We discuss the effect of epigenetics on β-cell regeneration for cell replacement therapy, the emerging bioinformatics approaches for analyzing the epigenetic contribution to type 2 diabetes mellitus (T2DM), the epigenetic core of the transgenerational inheritance hypothesis in T2DM, and the epigenetic clinical trials on T2DM. Therefore, prevention or reversion of the epigenetic changes occurring during T2DM development may reduce the individual and societal burden of the disease.
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Affiliation(s)
- Linda Sommese
- a U.O.C. Clinical Immunology, Immunohematology, Transfusion Medicine and Transplant Immunology, Regional Reference Laboratory of Transplant Immunology , Department of Internal and Specialty Medicine , Azienda Ospedaliera Universitaria (AOU), Università degli Studi della Campania "Luigi Vanvitelli ," Italy.,b Department of Experimental Medicine , Second University of Naples , Italy
| | - Alberto Zullo
- c Department of Sciences and Technologies , University of Sannio , Benevento , Italy.,d CEINGE-Advanced Biotechnologies , Naples , Italy
| | | | - Rossella Fabbricini
- a U.O.C. Clinical Immunology, Immunohematology, Transfusion Medicine and Transplant Immunology, Regional Reference Laboratory of Transplant Immunology , Department of Internal and Specialty Medicine , Azienda Ospedaliera Universitaria (AOU), Università degli Studi della Campania "Luigi Vanvitelli ," Italy
| | - Andrea Soricelli
- e IRCCS Research Institute SDN , Naples , Italy.,f Department of Studies of Institutions and Territorial Systems , University of Naples Parthenope , Naples , Italy
| | - Claudio Napoli
- a U.O.C. Clinical Immunology, Immunohematology, Transfusion Medicine and Transplant Immunology, Regional Reference Laboratory of Transplant Immunology , Department of Internal and Specialty Medicine , Azienda Ospedaliera Universitaria (AOU), Università degli Studi della Campania "Luigi Vanvitelli ," Italy.,e IRCCS Research Institute SDN , Naples , Italy.,g Department of Medical, Surgical, Neurological, Metabolic and Geriatric Sciences , Second University of Naples , Italy
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Bastidas M, Showalter SA. Thermodynamic and structural determinants of differential Pdx1 binding to elements from the insulin and IAPP promoters. J Mol Biol 2013; 425:3360-77. [PMID: 23796517 DOI: 10.1016/j.jmb.2013.06.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Revised: 06/11/2013] [Accepted: 06/13/2013] [Indexed: 10/26/2022]
Abstract
In adult mammals, the production of insulin and other peptide hormones, such as the islet amyloid polypeptide (IAPP), is limited to β-cells due to tissue-specific expression of a set of transcription factors, the best known of which is pancreatic duodenal homeobox protein 1 (Pdx1). Like many homeodomain transcription factors, Pdx1 binds to a core DNA recognition sequence containing the tetranucleotide 5'-TAAT-3'; its consensus recognition element is 5'-CTCTAAT(T/G)AG-3'. Currently, a complete thermodynamic profile of Pdx1 binding to near-consensus and native promoter sequences has not been established, obscuring the mechanism of target site selection by this critical transcription factor. Strikingly, while Pdx1 responsive elements in the human insulin promoter conform to the pentanucleotide 5'-CTAAT-3' sequence, the Pdx1 responsive elements in the human iapp promoter all contain a substitution to 5'-TTAAT-3'. The crystal structure of Pdx1 bound to the consensus nucleotide sequence does not explain how Pdx1 identifies this natural variation, if it does at all. Here we report a combination of isothermal calorimetric titrations, NMR spectroscopy, and extensive multi-microsecond molecular dynamics calculations of Pdx1 that define its interactions with a panel of natural promoter elements and consensus-derived sequences. Our results show a small preference of Pdx1 for a C base 5' relative to the core TAAT promoter element. Molecular mechanics calculations, corroborated by experimental NMR data, lead to a rational explanation for sequence discrimination at this position. Taken together, our results suggest a molecular mechanism for differential Pdx1 affinity to elements from the insulin and iapp promoter sequences.
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Affiliation(s)
- Monique Bastidas
- Department of Chemistry, Pennsylvania State University, 104 Chemistry Building, University Park, PA 16802, USA.
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Reddy MA, Park JT, Natarajan R. Epigenetic modifications and diabetic nephropathy. Kidney Res Clin Pract 2012; 31:139-50. [PMID: 26894019 PMCID: PMC4716094 DOI: 10.1016/j.krcp.2012.07.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 06/30/2012] [Accepted: 07/09/2012] [Indexed: 01/15/2023] Open
Abstract
Diabetic nephropathy (DN) is a major complication associated with both type 1 and type 2 diabetes, and a leading cause of end-stage renal disease. Conventional therapeutic strategies are not fully efficacious in the treatment of DN, suggesting an incomplete understanding of the gene regulation mechanisms involved in its pathogenesis. Furthermore, evidence from clinical trials has demonstrated a "metabolic memory" of prior exposure to hyperglycemia that continues to persist despite subsequent glycemic control. This remains a major challenge in the treatment of DN and other vascular complications. Epigenetic mechanisms such as DNA methylation, nucleosomal histone modifications, and noncoding RNAs control gene expression through regulation of chromatin structure and function and post-transcriptional mechanisms without altering the underlying DNA sequence. Emerging evidence indicates that multiple factors involved in the etiology of diabetes can alter epigenetic mechanisms and regulate the susceptibility to diabetes complications. Recent studies have demonstrated the involvement of histone lysine methylation in the regulation of key fibrotic and inflammatory genes related to diabetes complications including DN. Interestingly, histone lysine methylation persisted in vascular cells even after withdrawal from the diabetic milieu, demonstrating a potential role of epigenetic modifications in metabolic memory. Rapid advances in high-throughput technologies in the fields of genomics and epigenomics can lead to the identification of genome-wide alterations in key epigenetic modifications in vascular and renal cells in diabetes. Altogether, these findings can lead to the identification of potential predictive biomarkers and development of novel epigenetic therapies for diabetes and its associated complications.
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Affiliation(s)
| | | | - Rama Natarajan
- Department of Diabetes, Beckman Research Institute of City of Hope, Duarte, California, USA
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Lu ZM, Zhou J, Wang X, Guan Z, Bai H, Liu ZJ, Su N, Pan K, Ji J, Deng D. Nucleosomes correlate with in vivo progression pattern of de novo methylation of p16 CpG islands in human gastric carcinogenesis. PLoS One 2012; 7:e35928. [PMID: 22558275 PMCID: PMC3338478 DOI: 10.1371/journal.pone.0035928] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Accepted: 03/23/2012] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND The exact relationship between nucleosome positioning and methylation of CpG islands in human pathogenesis is unknown. METHODOLOGY/PRINCIPAL FINDINGS In the present study, we characterized the nucleosome position within the p16 CpG island and established a seeding methylation-specific PCR (sMSP) assay based on bisulfite modification to enrich the p16 alleles containing methylated-CpG at the methylation "seeding" sites within its intron-1 in gastric carcinogenesis. The sMSP-positive rate in primary gastric carcinoma (GC) samples (36/40) was significantly higher than that observed in gastritis (19/45) or normal samples (7/13) (P<0.01). Extensive clone sequencing of these sMSP products showed that the density of methylated-CpGs in p16 CpG islands increased gradually along with the severity of pathological changes in gastric tissues. In gastritis lesions the methylation was frequently observed in the region corresponding to the exon-1 coding-nucleosome and the 5'UTR-nucleosome; the methylation was further extended to the region corresponding to the promoter-nucleosome in GC samples. Only few methylated-CpG sites were randomly detected within p16 CpG islands in normal tissues. The significantly inversed relationship between the p16 exon-1 methylation and its transcription was observed in GC samples. An exact p16 promoter-specific 83 bp-MSP assay confirms the result of sMSP (33/55 vs. 1/6, P<0.01). In addition, p16 methylation in chronic gastritis lesions significantly correlated with H. pylori infection; however, such correlation was not observed in GC specimens. CONCLUSIONS/SIGNIFICANCE It was determined that de novo methylation was initiated in the coding region of p16 exon-1 in gastritis, then progressed to its 5'UTR, and ultimately to the proximal promoter in GCs. Nucleosomes may function as the basic extension/progression unit of de novo methylation of p16 CpG islands in vivo.
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Affiliation(s)
- Zhe-Ming Lu
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Division of Cancer Etiology, Peking University Cancer Hospital and Institute, Beijing, China
| | - Jing Zhou
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Division of Cancer Etiology, Peking University Cancer Hospital and Institute, Beijing, China
| | - Xiuhong Wang
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Division of Cancer Etiology, Peking University Cancer Hospital and Institute, Beijing, China
| | - Zhenpo Guan
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Division of Cancer Etiology, Peking University Cancer Hospital and Institute, Beijing, China
| | - Hua Bai
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Division of Cancer Etiology, Peking University Cancer Hospital and Institute, Beijing, China
| | - Zhao-Jun Liu
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Division of Cancer Etiology, Peking University Cancer Hospital and Institute, Beijing, China
| | - Na Su
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Division of Cancer Etiology, Peking University Cancer Hospital and Institute, Beijing, China
| | - Kaifeng Pan
- Department of Epidemiology, Peking University Cancer Hospital and Institute, Beijing, China
| | - Jiafu Ji
- Department of Surgery, Peking University Cancer Hospital and Institute, Beijing, China
| | - Dajun Deng
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Division of Cancer Etiology, Peking University Cancer Hospital and Institute, Beijing, China
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6
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Wilson LM, Wong SHK, Yu N, Geras-Raaka E, Raaka BM, Gershengorn MC. Insulin but not glucagon gene is silenced in human pancreas-derived mesenchymal stem cells. Stem Cells 2010; 27:2703-11. [PMID: 19785038 DOI: 10.1002/stem.229] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
We previously characterized human islet-derived precursor cells (hIPCs) as a specific type of mesenchymal stem cell capable of differentiating to insulin (INS)- and glucagon (GCG)-expressing cells. However, during proliferative expansion, INS transcript becomes undetectable and then cannot be induced, a phenomenon consistent with silencing of the INS gene. We explored this possibility by determining whether ectopic expression of transcription factors known to induce transcription of this gene in beta cells, pancreatic and duodenal homeobox factor 1 (Pdx1), V-maf musculoaponeurotic fibrosarcoma oncogene homolog A (Mafa), and neurogenic differentiation 1 (Neurod1), would activate INS gene expression in long-term hIPC cultures. Coexpression of all three transcription factors had little effect on INS mRNA levels but unexpectedly increased GCG mRNA at least 100,000-fold. In contrast to the endogenous promoter, an exogenous rat INS promoter was activated by expression of Pdx1 and Mafa in hIPCs. Chromatin immunoprecipitation (ChIP) assays using antibodies directed at posttranslationally modified histones show that regions of the INS and GCG genes have similar levels of activation-associated modifications but the INS gene has higher levels of repression-associated modifications. Furthermore, the INS gene was found to be less accessible to micrococcal nuclease digestion than the GCG gene. Lastly, ChIP assays show that exogenously expressed Pdx1 and Mafa bind at very low levels to the INS promoter and at 20- to 25-fold higher levels to the GCG promoter in hIPCs. We conclude that the INS gene in hIPCs is modified epigenetically ("silenced") so that it is resistant to activation by transcription factors.
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Affiliation(s)
- Leah M Wilson
- Clinical Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-8029, USA
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7
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Aviv V, Meivar-Levy I, Rachmut IH, Rubinek T, Mor E, Ferber S. Exendin-4 promotes liver cell proliferation and enhances the PDX-1-induced liver to pancreas transdifferentiation process. J Biol Chem 2009; 284:33509-20. [PMID: 19755420 DOI: 10.1074/jbc.m109.017608] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Over the last few years, evidence has accumulated revealing the unexpected potential of committed mammalian cells to convert to a different phenotype via a process called transdifferentiation or adult cell reprogramming. These findings may have major practical implications because this process may facilitate the generation of functional autologous tissues that can be used for replacing malfunctioning organs. An instructive role for transcription factors in diverting the developmental fate of cells in adult tissues has been demonstrated when adult human liver cells were induced to transdifferentiate to the pancreatic endocrine lineage upon ectopic expression of the pancreatic master regulator PDX-1 (pancreatic and duodenal homeobox gene 1). Since organogenesis and lineage commitment are affected also by developmental signals generated in response to environmental triggers, we have now analyzed whether the hormone GLP-1 (glucogen-like peptide-1) documented to play a role in pancreatic beta cell differentiation, maturation, and survival, can also increase the efficiency of liver to pancreas transdifferentiation. We demonstrate that the GLP-1R agonist, exendin-4, significantly improves the efficiency of PDX-1-mediated transdifferentiation. Exendin-4 affects the transdifferentiation process at two distinct steps; it increases the proliferation of liver cells predisposed to transdifferentiated in response to PDX-1 and promotes the maturation of transdifferentiated cells along the pancreatic lineage. Liver cell reprogramming toward the pancreatic beta cell lineage has been suggested as a strategy for functional replacement of the ablated insulin-producing cells in diabetics. Understanding the cellular and molecular basis of the transdifferentiation process will allow us to increase the efficiency of the reprogramming process and optimize its therapeutic merit.
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Affiliation(s)
- Vered Aviv
- Endocrine Institute, Sheba Medical Center, Tel-Hashomer 52621, Israel
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8
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Abstract
Background Insulin is a critical component of metabolic control, and as such, insulin gene expression has been the focus of extensive study. DNA sequences that regulate transcription of the insulin gene and the majority of regulatory factors have already been identified. However, only recently have other components of insulin gene expression been investigated, and in this study we examine the role of DNA methylation in the regulation of mouse and human insulin gene expression. Methodology/Principal Findings Genomic DNA samples from several tissues were bisulfite-treated and sequenced which revealed that cytosine-guanosine dinucleotide (CpG) sites in both the mouse Ins2 and human INS promoters are uniquely demethylated in insulin-producing pancreatic beta cells. Methylation of these CpG sites suppressed insulin promoter-driven reporter gene activity by almost 90% and specific methylation of the CpG site in the cAMP responsive element (CRE) in the promoter alone suppressed insulin promoter activity by 50%. Methylation did not directly inhibit factor binding to the CRE in vitro, but inhibited ATF2 and CREB binding in vivo and conversely increased the binding of methyl CpG binding protein 2 (MeCP2). Examination of the Ins2 gene in mouse embryonic stem cell cultures revealed that it is fully methylated and becomes demethylated as the cells differentiate into insulin-expressing cells in vitro. Conclusions/Significance Our findings suggest that insulin promoter CpG demethylation may play a crucial role in beta cell maturation and tissue-specific insulin gene expression.
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9
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Affiliation(s)
- Douglas R Cavener
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania, USA.
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10
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Sun F, Xie Q, Ma J, Yang S, Chen Q, Hong A. Nuclear factor Y is required for basal activation and chromatin accessibility of fibroblast growth factor receptor 2 promoter in osteoblast-like cells. J Biol Chem 2008; 284:3136-3147. [PMID: 19047043 PMCID: PMC2631964 DOI: 10.1074/jbc.m808992200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Fibroblast growth factor receptor 2 (FGFR2) plays an important regulatory
role in bone development. However, the regulatory mechanisms controlling FGFR2
expression remain poorly understood. Here we have identified a role for the
nuclear factor Y (NF-Y) in constitutive activation of FGFR2. A unique DNase I
hypersensitive site was detected in the region encompassing nucleotides -270
to +230 after scanning a large range covering 33.3 kilobases around the
transcription start site of FGFR2. Using a PCR-based chromatin accessibility
assay, an open chromatin conformation was detected around the proximal
5′ fragment of FGFR2 gene. Deletion constructs of the 5′-flanking
region of FGFR2 were fused to a luciferase reporter gene. After transient
transfection in C3H10T1/2, ME3T3-E1, and C2C12 as well as primary osteoblasts,
a minimal region -86/+139 that is highly homologous to the human sequence and
bears a CCAAT box was identified as the core promoter. Electrophoretic
mobility shift assay supershift and chromatin immunoprecipitation demonstrated
that the CCAAT box was the binding site for NF-Y. Deletion of NF-Y consensus
sequence resulted in the total loss of NF-Y promoter activity. Overexpression
of NF-Y protein and transfection of NF-Y small interfering RNAs in the cells
substantially changed the promoter activity. Moreover, NF-Y small interfering
RNAs greatly inhibited the endogenous FGFR2 transcription level and the
chromatin accessibility and H3 acetylation across the promoter. Taken
together, our results demonstrate that interaction of NF-Y at the CCAAT box is
pivotal to FGFR2 gene transcription partly through the construction of a local
open chromatin configuration across the promoter.
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Affiliation(s)
- Fenyong Sun
- Institute of Genetic Engineering, Jinan University, National Engineering Research Center of Genetic Medicine, Key Lab for Genetic Medicine of Guangdong Province, Guangzhou 510632, China
| | - Qiuling Xie
- Institute of Genetic Engineering, Jinan University, National Engineering Research Center of Genetic Medicine, Key Lab for Genetic Medicine of Guangdong Province, Guangzhou 510632, China
| | - Ji Ma
- Institute of Genetic Engineering, Jinan University, National Engineering Research Center of Genetic Medicine, Key Lab for Genetic Medicine of Guangdong Province, Guangzhou 510632, China
| | - Songhai Yang
- Shaoguan Tielu Hospital, Shaoguan, 512023, Guangdong, China
| | - Qiongyu Chen
- Institute of Genetic Engineering, Jinan University, National Engineering Research Center of Genetic Medicine, Key Lab for Genetic Medicine of Guangdong Province, Guangzhou 510632, China
| | - An Hong
- Institute of Genetic Engineering, Jinan University, National Engineering Research Center of Genetic Medicine, Key Lab for Genetic Medicine of Guangdong Province, Guangzhou 510632, China.
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Abstract
Production and secretion of insulin from the β-cells of the pancreas is very crucial in maintaining normoglycaemia. This is achieved by tight regulation of insulin synthesis and exocytosis from the β-cells in response to changes in blood glucose levels. The synthesis of insulin is regulated by blood glucose levels at the transcriptional and post-transcriptional levels. Although many transcription factors have been implicated in the regulation of insulin gene transcription, three β-cell-specific transcriptional regulators, Pdx-1 (pancreatic and duodenal homeobox-1), NeuroD1 (neurogenic differentiation 1) and MafA (V-maf musculoaponeurotic fibrosarcoma oncogene homologue A), have been demonstrated to play a crucial role in glucose induction of insulin gene transcription and pancreatic β-cell function. These three transcription factors activate insulin gene expression in a co-ordinated and synergistic manner in response to increasing glucose levels. It has been shown that changes in glucose concentrations modulate the function of these β-cell transcription factors at multiple levels. These include changes in expression levels, subcellular localization, DNA-binding activity, transactivation capability and interaction with other proteins. Furthermore, all three transcription factors are able to induce insulin gene expression when expressed in non-β-cells, including liver and intestinal cells. The present review summarizes the recent findings on how glucose modulates the function of the β-cell transcription factors Pdx-1, NeuroD1 and MafA, and thereby tightly regulates insulin synthesis in accordance with blood glucose levels.
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12
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Oduro AK, Fritsch MK, Murdoch FE. Chromatin context dominates estrogen regulation of pS2 gene expression. Exp Cell Res 2008; 314:2796-810. [PMID: 18662686 DOI: 10.1016/j.yexcr.2008.07.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2008] [Revised: 07/07/2008] [Accepted: 07/07/2008] [Indexed: 12/29/2022]
Abstract
Chromatin structure and transcription factor activity collaborate to set the transcription level of a gene. Our understanding of the relative contributions of each of these factors at a specific gene is limited. We studied the effects of an altered chromatin environment on the activity of the estrogen-responsive pS2 promoter. We created stable cell lines with the pS2 promoter situated in an alternative chromatin site in addition to it being in its native site. Both promoters were estrogen-responsive for estrogen receptor alpha (ERalpha) recruitment, but transcription was inducible only at the native site. At the recombinant site, transcription was high and constitutive. Higher histone H3 and H4 acetylation (acH3 and acH4), as well as trimethylated lysine 4 on histone H3 levels, was observed at the recombinant site compared to the native site in vehicle treated cells. Inhibition of histone deacetylases (HDACs) resulted in increased acH4, but only modest increases in acH3, ERalpha binding and basal transcription at the native pS2 site. Inhibiting HDACs had no effect on transcription from the recombinant site. These data suggest that highly active chromatin is not only permissive for transcription, but can override the requirement for the transcription factor at an inducible promoter.
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Affiliation(s)
- Akua K Oduro
- Department of Pathology and Laboratory Medicine, University of Wisconsin-Madison, MSC 5250, 1300 University Avenue, Madison, WI 53706, USA
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13
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Babu DA, Chakrabarti SK, Garmey JC, Mirmira RG. Pdx1 and BETA2/NeuroD1 participate in a transcriptional complex that mediates short-range DNA looping at the insulin gene. J Biol Chem 2008; 283:8164-72. [PMID: 18252719 DOI: 10.1074/jbc.m800336200] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The activity of the insulin gene, Ins, in islet beta cells is thought to arise in part from the synergistic action of the transcription factors Pdx1 and BETA2/NeuroD1. We asked how the binding of these factors to A and E elements many tens or hundreds of base pairs upstream of the start site could influence activity of transcriptional machinery. We therefore tested the hypothesis that the complex of Pdx1 and BETA2/NeuroD1 maintains a DNA conformation such that distal regions of the gene are brought into proximity of the promoter and coding region. We show by coimmunoprecipitation that Pdx1 and BETA2/NeuroD1 exist within a complex and that the two physically interact with one another in this complex as assessed by fluorescence resonance energy transfer. Consistent with this interaction, we found that the two factors simultaneously occupy the same fragment of the Ins gene in beta cell lines using the chromatin immunoprecipitation/re-chromatin immunoprecipitation assay. Using a modification of the chromosome conformation capture assay in vitro and in beta cells, we observed that Pdx1 and BETA2/NeuroD1 mediate looping of a segment of Ins that brings EcoRI sites located at -623 and +761 bp (relative to the transcriptional start site) in proximity to one another. This looping appears to be dependent in vitro upon an intact A3 binding element, but not upon the E2 element. Based on our findings, we propose a model whereby Pdx1 and BETA2/NeuroD1 physically interact to form a nucleoprotein complex on the Ins gene that mediates formation of a short DNA loop. Our results suggest that such short loop conformations may be a general mechanism to permit interactions between transcription factors and basal transcriptional machinery.
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Affiliation(s)
- Daniella A Babu
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
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Babu DA, Deering TG, Mirmira RG. A feat of metabolic proportions: Pdx1 orchestrates islet development and function in the maintenance of glucose homeostasis. Mol Genet Metab 2007; 92:43-55. [PMID: 17659992 PMCID: PMC2042521 DOI: 10.1016/j.ymgme.2007.06.008] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2007] [Revised: 06/14/2007] [Accepted: 06/15/2007] [Indexed: 01/30/2023]
Abstract
Emerging evidence over the past decade indicates a central role for transcription factors in the embryonic development of pancreatic islets and the consequent maintenance of normal glucose homeostasis. Pancreatic and duodenal homeobox 1 (Pdx1) is the best studied and perhaps most important of these factors. Whereas deletion or inactivating mutations of the Pdx1 gene causes whole pancreas agenesis in both mice and humans, even haploinsufficiency of the gene or alterations in its expression in mature islet cells causes substantial impairments in glucose tolerance and the development of a late-onset form of diabetes known as maturity onset diabetes of the young. The study of Pdx1 has revealed crucial phenotypic interrelationships of the varied cell types within the pancreas, particularly as these impinge upon cellular differentiation in the embryo and neogenesis and regeneration in the adult. In this review, we describe the actions of Pdx1 in the developing and mature pancreas and attempt to unify these actions with its known roles in modulating transcriptional complex formation and chromatin structure at the molecular genetic level.
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Affiliation(s)
- Daniella A. Babu
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908 USA
| | - Tye G. Deering
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908 USA
| | - Raghavendra G. Mirmira
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908 USA
- Diabetes Center, Department of Medicine, University of Virginia, Charlottesville, VA 22908 USA
- To whom correspondence should be addressed: University of Virginia Health System, 450 Ray C. Hunt Drive, Box 801407, Charlottesville, VA 22908. E-mail: , Telephone: 434-924-9416, Fax: 434-982-3796
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Evans-Molina C, Garmey JC, Ketchum R, Brayman KL, Deng S, Mirmira RG. Glucose regulation of insulin gene transcription and pre-mRNA processing in human islets. Diabetes 2007; 56:827-35. [PMID: 17327454 PMCID: PMC3705758 DOI: 10.2337/db06-1440] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Glucose is the primary regulator of insulin granule release from pancreatic islets. In rodent islets, the role of glucose in the acute regulation of insulin gene transcription has remained unclear, primarily because the abundance and long half-life of insulin mRNA confounds analysis of transcription by traditional methods that measure steady-state mRNA levels. To investigate the nature of glucose-regulated insulin gene transcription in human islets, we first quantitated the abundance and half-lives of insulin mRNA and pre-mRNAs after addition of actinomycin D (to stop transcription). Our results indicated that intron 1-and intron 2-containing pre-mRNAs were approximately 150- and 2,000-fold less abundant, respectively, than mature mRNA. 5' intron 2-containing pre-mRNAs displayed half-lives of only approximately 60 min, whereas all other transcripts displayed more extended lifetimes. In response to elevated glucose, pre-mRNA species increased within 60 min, whereas increases in mature mRNA did not occur until 48 h, suggesting that measurement of mature mRNA species does not accurately reflect the acute transcriptional response of the insulin gene to glucose. The acute increase in pre-mRNA species was preceded by a sixfold increase in histone H4 acetylation and a twofold increase in RNA polymerase II recruitment at the insulin promoter. Taken together, our data suggest that pre-mRNA species may be a more reliable reflection of acute changes to human insulin gene transcriptional rates and that glucose acutely enhances insulin transcription by a mechanism that enhances chromatin accessibility and leads to recruitment of basal transcriptional machinery.
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Affiliation(s)
| | - James C. Garmey
- Department of Medicine, University of Virginia, Charlottesville, Virginia
| | - Robert Ketchum
- Department of Surgery, University of Virginia, Charlottesville, Virginia
| | - Kenneth L. Brayman
- Department of Surgery, University of Virginia, Charlottesville, Virginia
| | - Shaoping Deng
- Human Islet Laboratory, Department of Surgery, University of Pennsylvania, Philadelphia, Pennsylvania
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