scholarly journals Zinc protoporphyrin binding to telomerase complexes and inhibition of telomerase activity*

2021 ◽  
Vol 9 (6) ◽  
Author(s):  
Zhaowen Zhu ◽  
Huy Tran ◽  
Meleah M. Mathahs ◽  
Brian D. Fink ◽  
John A. Albert ◽  
...  
Keyword(s):  
Telomerase Activity ◽  
Zinc Protoporphyrin

scholarly journals Zinc Protoporphyrin Binding to Telomerase Complexes and Inhibition of Telomerase Activity

2021 ◽  
Author(s):  
Zhaowen Zhu ◽  
Huy Tran ◽  
Meleah M. Mathahs ◽  
Brian D. Fink ◽  
John A. Albert ◽  
...  
Keyword(s):  
Dna Synthesis ◽  
Gel Electrophoresis ◽  
Cellular Proliferation ◽  
Telomerase Activity ◽  
Zinc Protoporphyrin ◽  
Agarose Gel ◽  
Agarose Gel Electrophoresis ◽  
Metaphase Chromosomes ◽  
Intact Cells ◽  
Confocal Fluorescence

Abstract Background: Zinc protoporphyrin (ZnPP) is a naturally occurring metalloprotoporphyrin (MPP) that is currently under development as a chemotherapeutic agent although its mechanism is unclear. Similar to natural and synthetic porphyrins, MPPs are thought to bind DNA and stabilize secondary structures such as guanine quadruplexes (G-4) and thus potentially impact telomerase activity and DNA synthesis which are important targets for chemotherapy. Interactions of MPPs with telomerase have not been previously reported. Methods: We wished to evaluate the effects of common MPPs, i.e., ZnPP, tin protoporphyrin (SnPP), and iron protoporphyrin (FePP), on cellular proliferation, apoptosis, and telomerase activity in hepatoma cells. The cytotoxicities of porphyrins were determined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay. Native agarose gel electrophoresis was used to identify ZnPP binding of telomerase complexes. Inhibition of telomerase activity by ZnPP was assessed by conventional telomeric repeat amplification protocol (TRAP) and direct telomerase activity assays. Colocalization of ZnPP with telomerase was analyzed with immunofluorescence staining and confocal microscopic analysis. Results: ZnPP was the most effective MPP for decreasing DNA synthesis and cellular proliferation, while promoting apoptosis in cultured hepatocytes. Concurrently, ZnPP down-regulated telomerase expression and was the best overall inhibitor of telomerase activity in intact cells and in vitro assays, with IC50 and EC50 values of ca 2.5 and 6 µM respectively. The natural fluorescence properties of ZnPP enabled direct imaging in cellular fractions using non-denaturing agarose gel electrophoresis, western blots, and confocal fluorescence microscopy. ZnPP localized to large cellular complexes (> 600kD) that contained telomerase and dyskerin as confirmed with immunocomplex mobility shift, immunoprecipitation, and immunoblot analyses. Confocal fluorescence studies showed that ZnPP co-localized with telomerase reverse transcriptase (TERT) and telomeres in the nucleus of synchronized S-phase cells. ZnPP also co-localized with TERT in the perinuclear regions of log phase cells but did not co-localize with telomeres on the ends of metaphase chromosomes, a site known to be devoid of telomerase complexes. Taken together, these results suggest that ZnPP does not bind to telomeric sequences per se, but alternatively, interacts with other structural components of the telomerase complex to inhibit telomerase enzymatic activity. Conclusions. ZnPP can actively interfere with telomerase activity in neoplastic cells, thus eliciting pro-apoptotic and anti-proliferative properties. These data support further development of natural or synthetic protoporphyrins for use as chemotherapeutic agents to augment current treatment protocols for a number of neoplasms.

Effects of Ganoderma lucidum (Higher Basidiomycetes) Extracts on the miRNA Profile and Telomerase Activity of the MCF-7 Breast Cancer Cell Line

2015 ◽  
Vol 17 (3) ◽  
pp. 231-239 ◽  
Author(s):  
Oyku Gonul ◽  
Hikmet Hakan Aydin ◽  
Erbil Kalmis ◽  
Husniye Kayalar ◽  
Ali Burak Ozkaya ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cell Line ◽  
Cancer Cell ◽  
Breast Cancer Cell ◽  
Breast Cancer Cell Line ◽  
Ganoderma Lucidum ◽  
Cancer Cell Line ◽  
Telomerase Activity ◽  
Mirna Profile ◽  
Mcf 7

Efficacy of decitabine in malignant meningioma cells: relation to promoter demethylation of distinct tumor suppressor and oncogenes and independence from TERT

2020 ◽  
pp. 1-10
Author(s):  
Louise Stögbauer ◽  
Christian Thomas ◽  
Andrea Wagner ◽  
Nils Warneke ◽  
Eva Christine Bunk ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Tumor Suppressor ◽  
Promoter Methylation ◽  
Tumor Suppressor Genes ◽  
Telomerase Activity ◽  
High Grade ◽  
Htert Promoter ◽  
Men 1 ◽  
Meningioma Cell ◽  
Tert Expression

OBJECTIVEChemotherapeutic options for meningiomas refractory to surgery or irradiation are largely unknown. Human telomerase reverse transcriptase (hTERT) promoter methylation with subsequent TERT expression and telomerase activity, key features in oncogenesis, are found in most high-grade meningiomas. Therefore, the authors investigated the impact of the demethylating agent decitabine (5-aza-2ʹ-deoxycytidine) on survival and DNA methylation in meningioma cells.METHODShTERT promoter methylation, telomerase activity, TERT expression, and cell viability and proliferation were investigated prior to and after incubation with decitabine in two benign (HBL-52 and Ben-Men 1) and one malignant (IOMM-Lee) meningioma cell line. The global effects of decitabine on DNA methylation were additionally explored with DNA methylation profiling.RESULTSHigh levels of TERT expression, telomerase activity, and hTERT promoter methylation were found in IOMM-Lee and Ben-Men 1 but not in HBL-52 cells. Decitabine induced a dose-dependent significant decrease of proliferation and viability after incubation with doses from 1 to 10 μM in IOMM-Lee but not in HBL-52 or Ben-Men 1 cells. However, effects in IOMM-Lee cells were not related to TERT expression, telomerase activity, or hTERT promoter methylation. Genome-wide methylation analyses revealed distinct demethylation of 14 DNA regions after drug administration in the decitabine-sensitive IOMM-Lee but not in the decitabine-resistant HBL-52 cells. Differentially methylated regions covered promoter regions of 11 genes, including several oncogenes and tumor suppressor genes that to the authors’ knowledge have not yet been described in meningiomas.CONCLUSIONSDecitabine decreases proliferation and viability in high-grade but not in benign meningioma cell lines. The effects of decitabine are TERT independent but related to DNA methylation changes of promoters of distinct tumor suppressor genes and oncogenes.

Lead poisoning: Zinc protoporphyrin in blood of children from Santo Amaro da Purificação, Bahia, Brazil

1996 ◽  
Vol 72 (5) ◽  
pp. 295-298 ◽  
Author(s):  
Fernando M. Carvalho ◽  
Annibal M. S. Neto ◽  
Maria F. T. Peres ◽  
Henrique R. Gonçalves ◽  
Gustavo Cardoso Guimarães ◽  
...  
Keyword(s):  
Lead Poisoning ◽  
Zinc Protoporphyrin

scholarly journals Bi-allelic MCM10 variants associated with immune dysfunction and cardiomyopathy cause telomere shortening

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ryan M. Baxley ◽  
Wendy Leung ◽  
Megan M. Schmit ◽  
Jacob Peter Matson ◽  
Lulu Yin ◽  
...  
Keyword(s):  
Immune Cell ◽  
Nk Cell ◽  
Restrictive Cardiomyopathy ◽  
Telomerase Activity ◽  
Compound Heterozygous ◽  
Minichromosome Maintenance ◽  
Telomere Shortening ◽  
Clinical Phenotypes ◽  
Eukaryotic Dna ◽  
Minichromosome Maintenance Protein

AbstractMinichromosome maintenance protein 10 (MCM10) is essential for eukaryotic DNA replication. Here, we describe compound heterozygous MCM10 variants in patients with distinctive, but overlapping, clinical phenotypes: natural killer (NK) cell deficiency (NKD) and restrictive cardiomyopathy (RCM) with hypoplasia of the spleen and thymus. To understand the mechanism of MCM10-associated disease, we modeled these variants in human cell lines. MCM10 deficiency causes chronic replication stress that reduces cell viability due to increased genomic instability and telomere erosion. Our data suggest that loss of MCM10 function constrains telomerase activity by accumulating abnormal replication fork structures enriched with single-stranded DNA. Terminally-arrested replication forks in MCM10-deficient cells require endonucleolytic processing by MUS81, as MCM10:MUS81 double mutants display decreased viability and accelerated telomere shortening. We propose that these bi-allelic variants in MCM10 predispose specific cardiac and immune cell lineages to prematurely arrest during differentiation, causing the clinical phenotypes observed in both NKD and RCM patients.

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