- Browse by Author
Browsing by Author "Dong, X. Charlie"
Now showing 1 - 10 of 48
Results Per Page
Sort Options
Item Aberrant gene expression induced by a high fat diet is linked to H3K9 acetylation in the promoter-proximal region(Elsevier, 2021-03) Morral, Núria; Liu, Sheng; Conteh, Abass M.; Chu, Xiaona; Wang, Yue; Dong, X. Charlie; Liu, Yunlong; Linnemann, Amelia K.; Wan, Jun; Medical and Molecular Genetics, School of MedicineNon-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease, with an estimated global prevalence of 1 in 4 individuals. Aberrant transcriptional control of gene expression is central to the pathophysiology of metabolic diseases. However, the molecular mechanisms leading to gene dysregulation are not well understood. Histone modifications play important roles in the control of transcription. Acetylation of histone 3 at lysine 9 (H3K9ac) is associated with transcriptional activity and is implicated in transcript elongation by controlling RNA polymerase II (RNAPII) pause-release. Hence, changes in this histone modification may shed information on novel pathways linking transcription control and metabolic dysfunction. Here, we carried out genome-wide analysis of H3K9ac in the liver of mice fed a control or a high-fat diet (an animal model of NAFLD), and asked whether this histone mark associates with changes in gene expression. We found that over 70% of RNAPII peaks in promoter-proximal regions overlapped with H3K9ac, consistent with a role of H3K9ac in the regulation of transcription. When comparing high-fat with control diet, approximately 17% of the differentially expressed genes were associated with changes in H3K9ac in their promoters, showing a strong correlation between changes in H3K9ac signal and gene expression. Overall, our data indicate that in response to a high-fat diet, dysregulated gene expression of a subset of genes may be attributable to changes in transcription elongation driven by H3K9ac. Our results point at an added mechanism of gene regulation that may be important in the development of metabolic diseases.Item ATG14 plays a critical role in hepatic lipid droplet homeostasis(Elsevier, 2023) Huang, Menghao; Zhang, Yang; Park, Jimin; Chowdhury, Kushan; Xu, Jiazhi; Lu, Alex; Wang, Lu; Zhang, Wenjun; Ekser, Burcin; Yu, Liqing; Dong, X. Charlie; Biochemistry and Molecular Biology, School of MedicineBackground & aims: Autophagy-related 14 (ATG14) is a key regulator of autophagy. ATG14 is also localized to lipid droplet; however, the function of ATG14 on lipid droplet remains unclear. In this study, we aimed to elucidate the role of ATG14 in lipid droplet homeostasis. Methods: ATG14 loss-of-function and gain-of-function in lipid droplet metabolism were analyzed by fluorescence imaging in ATG14 knockdown or overexpression hepatocytes. Specific domains involved in the ATG14 targeting to lipid droplets were analyzed by deletion or site-specific mutagenesis. ATG14-interacting proteins were analyzed by co-immunoprecipitation. The effect of ATG14 on lipolysis was analyzed in human hepatocytes and mouse livers that were deficient in ATG14, comparative gene identification-58 (CGI-58), or both. Results: Our data show that ATG14 is enriched on lipid droplets in hepatocytes. Mutagenesis analysis reveals that the Barkor/ATG14 autophagosome targeting sequence (BATS) domain of ATG14 is responsible for the ATG14 localization to lipid droplets. Co-immunoprecipitation analysis illustrates that ATG14 interacts with adipose triglyceride lipase (ATGL) and CGI-58. Moreover, ATG14 also enhances the interaction between ATGL and CGI-58. In vitro lipolysis analysis demonstrates that ATG14 deficiency remarkably decreases triglyceride hydrolysis. Conclusions: Our data suggest that ATG14 can directly enhance lipid droplet breakdown through interactions with ATGL and CGI-58.Item Cell-Type Specific Function of STAT4 in an Animal Model of Multiple Sclerosis(2023-12) Alakhras, Nada S.; Kaplan, Mark H.; Cook-Mills, Joan; Dong, X. Charlie; Quilliam, Lawrence A.Signal transducer and activator of transcription 4 (STAT4) is a critical regulator of inflammation. STAT4 promotes protective immunity and autoimmunity downstream of pro-inflammatory cytokines including IL-12 and IL-23. In experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), germ-line deletion of STAT4 in mice results in resistance to the development of inflammation and paralysis. In parallel, genome-wide association studies (GWAS) have identified polymorphisms in the STAT4 gene associated with susceptibility to several autoimmune diseases including MS demonstrating a potential role for STAT4 in human autoimmunity. Here, we examined cell-type requirements for STAT4 in EAE. Using conditional Stat4 mutant mice, we found that mice lacking Stat4 in T cells and CD11c+-expressing cells are resistant to EAE, while mice lacking Stat4 in Lyz2+-expressing cells are susceptible to EAE. STAT4 is expressed and activated in CD11c+ dendritic cells (DCs) in the CNS during peak disease severity. Stat4fl/flCD11cCre mice exhibit significantly decreased classical dendritic cell (cDC) expansion in the CNS and this correlates with diminished numbers of infiltrated T cells in the CNS and decreased inflammatory cytokine production. Adoptive transfer of wild type but not Stat4-/- or Il23r-/- DCs into Stat4fl/flCD11cCre rescues the development of EAE. Transferred Il23r-/- DCs were retained in the lymph nodes suggesting that IL-23-STAT4 signaling promotes their migration to and expansion in the CNS. Single-cell RNA-seq analyses of CNS DCs from WT and Stat4fl/flCD11cCre mice identified cDC populations with STAT4-dependent gene expression and migratory phenotypes. Collectively, our results demonstrate that STAT4 in cDCs is required for expansion in the CNS, the development of encephalitogenic T cells, and the clinical symptoms of EAE. Thus, our study reveals previously unrecognized functions of STAT4 in cDCs that provide mechanistic insight into CNS autoimmunity and provide a foundation for identifying new therapeutic targets for the disease.Item A closer look at the mysterious HSD17B131(Elsevier, 2020-11) Dong, X. Charlie; Biochemistry and Molecular Biology, School of MedicineItem Conserved Residues in Murine Papillomavirus E2 Regulate the Viral Life Cycle(2024-12) Gonzalez, Jessica Kay; Androphy, Elliot J.; Dong, X. Charlie; Katzenellenbogen, Rachel; Robinson, ChristopherPapillomaviruses (PVs) are small, non-enveloped DNA viruses that infect the stratified epithelia. Once an infection is initiated, the virus must successfully navigate the three stages of its life cycle: establishment, maintenance, and vegetative amplification. A major mechanism of regulating this viral program is post-translational modification on the viral E2 protein, which is responsible for orchestrating viral transcription, replication, and genome partitioning. The hypothesis underscoring this work is that residues in E2 are highly conserved across PV types because they serve some structural or functional purpose for the virus. A targeted mutant library was generated in E2 from murine papillomavirus (MmuPV1) to investigate conserved residues that have been shown to be post-translationally modified in the E2 of other PVs, including BPV-1 and high-risk HPV-31. In the transactivation domain (TAD) tyrosine 102 and the lysine 112/113 motif were modified to their constitutively modified (phosphorylated and acetylated, respectively) or unmodified states, while cysteine 307 in the DNA binding and dimerization domain (DBD) was mutated to a less-reactive serine or DNA binding defective phenylalanine mutant. We characterized how mutation at each of these conserved sites alters E2 function using a battery of in vitro assays to assess for transcription and replication ability. We also studied how each mutant contributes to disease progression using an immunocompromised mouse model assessing cutaneous disease. We demonstrate that mutants which fail to replicate transiently in vitro will also fail to induce proliferative wart formation, establishing a predictive link between in vitro and in vivo experiments. Taken together, our findings suggest that modifications on conserved residues in E2 act as molecular switches that regulate E2 activity throughout the cellular and viral life cycle.Item Correction: Sirt1 coordinates with ERα to regulate autophagy and adiposity(Springer Nature, 2023-06-23) Tao, Zhipeng; Shi, Limin; Parke, Jane; Zheng, Louise; Gu, Wei; Dong, X. Charlie; Liu, Dongmin; Wang, Zongwei; Olumi, Aria F.; Cheng, Zhiyong; Biochemistry and Molecular Biology, School of MedicineThis corrects the article "Sirt1 coordinates with ERα to regulate autophagy and adiposity" in volume 7, 53.Item Discordant regulation of eIF2 kinase GCN2 and mTORC1 during nutrient stress(Oxford University Press, 2021-06-04) Misra, Jagannath; Holmes, Michael J.; Mirek, Emily T.; Langevin, Michael; Kim, Hyeong-Geug; Carlson, Kenneth R.; Watford, Malcolm; Dong, X. Charlie; Anthony, Tracy G.; Wek, Ronald C.; Biochemistry and Molecular Biology, School of MedicineAppropriate regulation of the Integrated stress response (ISR) and mTORC1 signaling are central for cell adaptation to starvation for amino acids. Halofuginone (HF) is a potent inhibitor of aminoacylation of tRNAPro with broad biomedical applications. Here, we show that in addition to translational control directed by activation of the ISR by general control nonderepressible 2 (GCN2), HF increased free amino acids and directed translation of genes involved in protein biogenesis via sustained mTORC1 signaling. Deletion of GCN2 reduced cell survival to HF whereas pharmacological inhibition of mTORC1 afforded protection. HF treatment of mice synchronously activated the GCN2-mediated ISR and mTORC1 in liver whereas Gcn2-null mice allowed greater mTORC1 activation to HF, resulting in liver steatosis and cell death. We conclude that HF causes an amino acid imbalance that uniquely activates both GCN2 and mTORC1. Loss of GCN2 during HF creates a disconnect between metabolic state and need, triggering proteostasis collapse.Item Endothelial dysfunction in pathological processes of chronic liver disease during aging(Wiley, 2022) Wan, Ying; Li, Xuedong; Slevin, Elise; Harrison, Kelly; Li, Tian; Zhang, Yudian; Klaunig, James E.; Wu, Chaodong; Shetty, Ashok K.; Dong, X. Charlie; Meng, Fanyin; Medicine, School of MedicineAging is associated with gradual changes in liver structure and physiological/pathological functions in hepatic cells including hepatocytes, cholangiocytes, Kupffer cells, hepatic stellate cells (HSCs), and liver sinusoidal endothelial cells (LSECs). LSECs are specialized hepatic endothelial cells that regulate liver homeostasis. These cells actively impact the hepatic microenvironment as they have fenestrations and a thin morphology to allow substance exchange between circulating blood and the liver tissue. As aging occurs, LSECs have a reduction in both the number and size of fenestrations, which is referred to as pseudocapillarization. This along with the aging of the liver leads to increased oxidative stress, decreased availability of nitric oxide, decreased hepatic blood flow, and increased inflammatory cytokines in LSECs. Vascular aging can also lead to hepatic hypoxia, HSC activation, and liver fibrosis. In this review, we described the basic structure of LSECs, and the effect of LSECs on hepatic inflammation and fibrosis during aging process. We briefly summarized the changes of hepatic microcirculation during liver inflammation, the effect of aging on the clearance function of LSECs, the interactions between LSECs and immunity, hepatocytes or other hepatic nonparenchymal cells, and the therapeutic intervention of liver diseases by targeting LSECs and vascular system. Since LSECs play an important role in the development of liver fibrosis and the changes of LSEC phenotype occur in the early stage of liver fibrosis, the study of LSECs in the fibrotic liver is valuable for the detection of early liver fibrosis and the early intervention of fibrotic response.Item The Essential Role of the Non-Essential Amino Acid Asparagine in Lymphoid Malignancies(2023-05) Srivastava, Sankalp; Zhang, Ji; Dong, X. Charlie; Mosley, Amber L.; Wek, Ronald C.Cancer cells display increased metabolic demands to support their proliferation and biosynthetic needs. It has been extensively shown in cancers, that amino acids have functions beyond the role of mRNA translation. The breadth of functions makes amino acid restriction an effective strategy for cancer therapy; hence an important line of research involves targeting amino acid acquisition and metabolism therapeutically. Currently, asparagine depletion via L-Asparaginase in acute lymphoblastic leukemia (ALL) remains the only clinically approved therapy to date. In the first project, we showed that ALL cells are auxotrophic for asparagine and rely on exogenous sources for this non-essential amino acid. However, sensitivity to L-Asparaginase therapy is mitigated by the expression of the enzyme asparagine synthetase (ASNS), involved in de novo asparagine biosynthesis. We showed that this adaptive response requires two essential steps; demethylation of the ASNS promoter and recruitment of activating transcription factor 4 (ATF4) to the promoter to drive ASNS transcription. Our follow-up study in ALL cells showed that asparagine bioavailability (through de novo biosynthesis or exogenous sources) is essential to maintain the expression of the critical oncogene c-MYC. c-MYC is a potent transcription factor and is dysregulated in over 60% of cancers, including hematopoietic malignancies. We showed that this regulation by asparagine is primarily at the translation level and c-MYC expression is rescued only when exogenous asparagine is available or when cells can undertake de novo biosynthesis. At the biochemical level, asparagine depletion also causes an induction of ATF4 mediated stress response and suppression of global translation mediated by decreased mammalian target of rapamycin complex 1 (mTORC1) activity. However, we found that neither inhibition of the stress response or rescuing global translation rescued c-MYC protein expression. We also extended this observation to c-MYC-driven lymphomas using cell lines and orthotopic in vivo models. We showed that genetic inhibition of ASNS or pharmacological inhibition of asparagine production can significantly limit c-MYC protein and tumor growth when environmental asparagine is limiting. Overall, our work shows an essential role for asparagine in lymphoid cancers and has expanded on the usage of L-Asparaginase to resistant leukemias and lymphomas.Item Fabp4-Cre-mediated Sirt6 deletion impairs adipose tissue function and metabolic homeostasis in mice(BioScientifica, 2017-06) Xiong, Xiwen; Zhang, Cuicui; Zhang, Yang; Fan, Rui; Qian, Xinlai; Dong, X. Charlie; Biochemistry and Molecular Biology, School of MedicineSIRT6 is a member of sirtuin family of deacetylases involved in diverse processes including genome stability, metabolic homeostasis and anti-inflammation. However, its function in the adipose tissue is not well understood. To examine the metabolic function of SIRT6 in the adipose tissue, we generated two mouse models that are deficient in Sirt6 using the Cre-lox approach. Two commonly used Cre lines that are driven by either the mouse Fabp4 or Adipoq gene promoter were chosen for this study. The Sirt6-knockout mice generated by the Fabp4-Cre line (Sirt6f/f:Fabp4-Cre) had a significant increase in both body weight and fat mass and exhibited glucose intolerance and insulin resistance as compared with the control wild-type mice. At the molecular levels, the Sirt6f/f :Fabp4-Cre-knockout mice had increased expression of inflammatory genes including F4/80, TNFα, IL-6 and MCP-1 in both white and brown adipose tissues. Moreover, the knockout mice showed decreased expression of the adiponectin gene in the white adipose tissue and UCP1 in the brown adipose tissue, respectively. In contrast, the Sirt6 knockout mice generated by the Adipoq-Cre line (Sirt6f/f :Adipoq-Cre) only had modest insulin resistance. In conclusion, our data suggest that the function of SIRT6 in the Fabp4-Cre-expressing cells in addition to mature adipocytes plays a critical role in body weight maintenance and metabolic homeostasis.