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Huan MJ, Fu PP, Chen X, Wang ZX, Ma ZR, Cai SZ, Jiang Q, Wang Q. Identification of the central role of RNA polymerase mitochondrial for angiogenesis. Cell Commun Signal 2024; 22:343. [PMID: 38907279 PMCID: PMC11191269 DOI: 10.1186/s12964-024-01712-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Accepted: 06/10/2024] [Indexed: 06/23/2024] Open
Abstract
Mitochondria are central to endothelial cell activation and angiogenesis, with the RNA polymerase mitochondrial (POLRMT) serving as a key protein in regulating mitochondrial transcription and oxidative phosphorylation. In our study, we examined the impact of POLRMT on angiogenesis and found that its silencing or knockout (KO) in human umbilical vein endothelial cells (HUVECs) and other endothelial cells resulted in robust anti-angiogenic effects, impeding cell proliferation, migration, and capillary tube formation. Depletion of POLRMT led to impaired mitochondrial function, characterized by mitochondrial depolarization, oxidative stress, lipid oxidation, DNA damage, and reduced ATP production, along with significant apoptosis activation. Conversely, overexpressing POLRMT promoted angiogenic activity in the endothelial cells. In vivo experiments demonstrated that endothelial knockdown of POLRMT, by intravitreous injection of endothelial specific POLRMT shRNA adeno-associated virus, inhibited retinal angiogenesis. In addition, inhibiting POLRMT with a first-in-class inhibitor IMT1 exerted significant anti-angiogenic impact in vitro and in vivo. Significantly elevated expression of POLRMT was observed in the retinal tissues of streptozotocin-induced diabetic retinopathy (DR) mice. POLRMT endothelial knockdown inhibited pathological retinal angiogenesis and mitigated retinal ganglion cell (RGC) degeneration in DR mice. At last, POLRMT expression exhibited a substantial increase in the retinal proliferative membrane tissues of human DR patients. These findings collectively establish the indispensable role of POLRMT in angiogenesis, both in vitro and in vivo.
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Affiliation(s)
- Meng-Jia Huan
- Department of Ophthalmology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China
- The Affiliated Eye Hospital, Nanjing Medical University, Nanjing, 210029, China
| | - Ping-Ping Fu
- Department of Ophthalmology, Shanghai Eye Diseases Prevention & Treatment Center, Shanghai Eye Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Xia Chen
- Department of Anesthesiology, Children's hospital of Soochow University, Suzhou, 215025, China
| | - Zhao-Xia Wang
- Department of Endocrinology, Fengcheng Hospital of Fengxian Distric, Shanghai, China
| | - Zhou-Rui Ma
- Department of Burn and Plastic Surgery, Children's Hospital of Soochow University, Suzhou, China
| | - Shi-Zhong Cai
- Department of Child and Adolescent Healthcare, Children's Hospital of Soochow University, Suzhou, China.
- Key Laboratory of Congenital Structural Malformations of Suzhou City, Suzhou, China.
| | - Qin Jiang
- The Affiliated Eye Hospital, Nanjing Medical University, Nanjing, 210029, China.
| | - Qian Wang
- Department of Anesthesiology, Children's hospital of Soochow University, Suzhou, 215025, China.
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Daglish SCD, Fennell EMJ, Graves LM. Targeting Mitochondrial DNA Transcription by POLRMT Inhibition or Depletion as a Potential Strategy for Cancer Treatment. Biomedicines 2023; 11:1598. [PMID: 37371693 PMCID: PMC10295849 DOI: 10.3390/biomedicines11061598] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 05/27/2023] [Accepted: 05/29/2023] [Indexed: 06/29/2023] Open
Abstract
Transcription of the mitochondrial genome is essential for the maintenance of oxidative phosphorylation (OXPHOS) and other functions directly related to this unique genome. Considerable evidence suggests that mitochondrial transcription is dysregulated in cancer and cancer metastasis and contributes significantly to cancer cell metabolism. Recently, inhibitors of the mitochondrial DNA-dependent RNA polymerase (POLRMT) were identified as potentially attractive new anti-cancer compounds. These molecules (IMT1, IMT1B) inactivate cancer cell metabolism through reduced transcription of mitochondrially-encoded OXPHOS subunits such as ND1-5 (Complex I) and COI-IV (Complex IV). Studies from our lab have discovered small molecule regulators of the mitochondrial matrix caseinolytic protease (ClpP) as probable inhibitors of mitochondrial transcription. These compounds activate ClpP proteolysis and lead to the rapid depletion of POLRMT and other matrix proteins, resulting in inhibition of mitochondrial transcription and growth arrest. Herein we present a comparison of POLRMT inhibition and ClpP activation, both conceptually and experimentally, and evaluate the results of these treatments on mitochondrial transcription, inhibition of OXPHOS, and ultimately cancer cell growth. We discuss the potential for targeting mitochondrial transcription as a cancer cell vulnerability.
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Affiliation(s)
| | | | - Lee M. Graves
- Department of Pharmacology and the Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; (S.C.D.D.); (E.M.J.F.)
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Yu HJ, Xiao GL, Zhao YY, Wang XX, Lan R. Targeting Mitochondrial Metabolism and RNA Polymerase POLRMT to Overcome Multidrug Resistance in Cancer. Front Chem 2022; 9:775226. [PMID: 34976949 PMCID: PMC8716502 DOI: 10.3389/fchem.2021.775226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 12/06/2021] [Indexed: 11/13/2022] Open
Abstract
Clinically, the prognosis of tumor therapy is fundamentally affected by multidrug resistance (MDR), which is primarily a result of enhanced drug efflux mediated by channels in the membrane that reduce drug accumulation in tumor cells. How to restore the sensitivity of tumor cells to chemotherapy is an ongoing and pressing clinical issue. There is a prevailing view that tumor cells turn to glycolysis for energy supply due to hypoxia. However, studies have shown that mitochondria also play crucial roles, such as providing intermediates for biosynthesis through the tricarboxylic acid (TCA) cycle and a plenty of ATP to fuel cells through the complete breakdown of organic matter by oxidative phosphorylation (OXPHOS). High OXPHOS have been found in some tumors, particularly in cancer stem cells (CSCs), which possess increased mitochondria mass and may be depends on OXPHOS for energy supply. Therefore, they are sensitive to inhibitors of mitochondrial metabolism. In view of this, we should consider mitochondrial metabolism when developing drugs to overcome MDR, where mitochondrial RNA polymerase (POLRMT) would be the focus, as it is responsible for mitochondrial gene expression. Inhibition of POLRMT could disrupt mitochondrial metabolism at its source, causing an energy crisis and ultimately eradicating tumor cells. In addition, it may restore the energy supply of MDR cells to glycolysis and re-sensitize them to conventional chemotherapy. Furthermore, we discuss the rationale and strategies for designing new therapeutic molecules for MDR cancers by targeting POLRMT.
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Affiliation(s)
- Hui-Jing Yu
- School of Pharmaceutical Sciences, Shenzhen University Health Science Center, Shenzhen, China
| | - Guan-Li Xiao
- School of Pharmaceutical Sciences, Shenzhen University Health Science Center, Shenzhen, China
| | - Yu-Ying Zhao
- Department of Cell Biology and Medical Genetics, School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, China
| | - Xin-Xin Wang
- Department of Cell Biology and Medical Genetics, School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, China
| | - Rongfeng Lan
- Department of Cell Biology and Medical Genetics, School of Basic Medical Sciences, Shenzhen University Health Science Center, Shenzhen, China
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Small-molecule inhibitors of human mitochondrial DNA transcription. Nature 2020; 588:712-716. [PMID: 33328633 DOI: 10.1038/s41586-020-03048-z] [Citation(s) in RCA: 100] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 10/22/2020] [Indexed: 01/31/2023]
Abstract
Altered expression of mitochondrial DNA (mtDNA) occurs in ageing and a range of human pathologies (for example, inborn errors of metabolism, neurodegeneration and cancer). Here we describe first-in-class specific inhibitors of mitochondrial transcription (IMTs) that target the human mitochondrial RNA polymerase (POLRMT), which is essential for biogenesis of the oxidative phosphorylation (OXPHOS) system1-6. The IMTs efficiently impair mtDNA transcription in a reconstituted recombinant system and cause a dose-dependent inhibition of mtDNA expression and OXPHOS in cell lines. To verify the cellular target, we performed exome sequencing of mutagenized cells and identified a cluster of amino acid substitutions in POLRMT that cause resistance to IMTs. We obtained a cryo-electron microscopy (cryo-EM) structure of POLRMT bound to an IMT, which further defined the allosteric binding site near the active centre cleft of POLRMT. The growth of cancer cells and the persistence of therapy-resistant cancer stem cells has previously been reported to depend on OXPHOS7-17, and we therefore investigated whether IMTs have anti-tumour effects. Four weeks of oral treatment with an IMT is well-tolerated in mice and does not cause OXPHOS dysfunction or toxicity in normal tissues, despite inducing a strong anti-tumour response in xenografts of human cancer cells. In summary, IMTs provide a potent and specific chemical biology tool to study the role of mtDNA expression in physiology and disease.
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Kartje ZJ, Janis HI, Mukhopadhyay S, Gagnon KT. Revisiting T7 RNA polymerase transcription in vitro with the Broccoli RNA aptamer as a simplified real-time fluorescent reporter. J Biol Chem 2020; 296:100175. [PMID: 33303627 PMCID: PMC7948468 DOI: 10.1074/jbc.ra120.014553] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 12/03/2020] [Accepted: 12/10/2020] [Indexed: 11/06/2022] Open
Abstract
Methods for rapid and high-throughput screening of transcription in vitro to examine reaction conditions, enzyme mutants, promoter variants, and small molecule modulators can be extremely valuable tools. However, these techniques may be difficult to establish or inaccessible to many researchers. To develop a straightforward and cost-effective platform for assessing transcription in vitro, we used the "Broccoli" RNA aptamer as a direct, real-time fluorescent transcript readout. To demonstrate the utility of our approach, we screened the effect of common reaction conditions and components on bacteriophage T7 RNA polymerase (RNAP) activity using a common quantitative PCR instrument for fluorescence detection. Several essential conditions for in vitro transcription by T7 RNAP were confirmed with this assay, including the importance of enzyme and substrate concentrations, covariation of magnesium and nucleoside triphosphates, and the effects of several typical additives. When we used this method to assess all possible point mutants of a canonical T7 RNAP promoter, our results coincided well with previous reports. This approach should translate well to a broad variety of bacteriophage in vitro transcription systems and provides a platform for developing fluorescence-based readouts of more complex transcription systems in vitro.
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Affiliation(s)
- Zachary J Kartje
- Department of Chemistry and Biochemistry, Southern Illinois University, Carbondale, Illinois, USA
| | - Helen I Janis
- Department of Chemistry and Biochemistry, Southern Illinois University, Carbondale, Illinois, USA
| | - Shaoni Mukhopadhyay
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois, USA
| | - Keith T Gagnon
- Department of Chemistry and Biochemistry, Southern Illinois University, Carbondale, Illinois, USA; Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois, USA.
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Dostal V, Churchill MEA. Cytosine methylation of mitochondrial DNA at CpG sequences impacts transcription factor A DNA binding and transcription. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2019; 1862:598-607. [PMID: 30807854 PMCID: PMC7806247 DOI: 10.1016/j.bbagrm.2019.01.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 01/21/2019] [Accepted: 01/23/2019] [Indexed: 12/22/2022]
Abstract
In eukaryotes, cytosine methylation of nuclear DNA at CpG sequences (5mCpG) regulates epigenetic inheritance through alterations in chromatin structure. However, mitochondria lack nucleosomal chromatin, therefore the molecular mechanisms by which 5mCpG influences mitochondria must be different and are as yet unknown. Mitochondrial Transcription Factor A (TFAM) is both the primary DNA-compacting protein in the mitochondrial DNA (mtDNA) nucleoid and a transcription-initiation factor. TFAM must encounter hundreds of CpGs in mtDNA, so the occurrence of 5mCpG has the potential to impact TFAM-DNA recognition. We used biophysical approaches to determine whether 5mCpG alters any TFAM-dependent activities. 5mCpG in the heavy strand promoter (HSP1) increased the binding affinity of TFAM and induced TFAM multimerization with increased cooperativity compared to nonmethylated DNA. However, 5mCpG had no apparent effect on TFAM-dependent DNA compaction. Additionally, 5mCpG had a clear and context-dependent effect on transcription initiating from the three mitochondrial promoters. Taken together, our findings demonstrate that 5mCpG in the mitochondrial promoter region does impact TFAM-dependent activities in vitro.
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Affiliation(s)
- Vishantie Dostal
- Program in Structural Biology and Biochemistry, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Mair E A Churchill
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA; Program in Structural Biology and Biochemistry, University of Colorado School of Medicine, Aurora, CO 80045, USA.
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