scholarly journals Helicases FANCJ, RTEL1 and BLM Act on Guanine Quadruplex DNA in Vivo

Genes ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 870 ◽  
Author(s):  
Peter Lansdorp ◽  
Niek van Wietmarschen
Keyword(s):  
Gene Expression ◽  
Genome Stability ◽  
Cell Function ◽  
Historical Context ◽  
Telomere Maintenance ◽  
Dna Structures ◽  
G4 Dna ◽  
Guanine Quadruplex

Guanine quadruplex (G4) structures are among the most stable secondary DNA structures that can form in vitro, and evidence for their existence in vivo has been steadily accumulating. Originally described mainly for their deleterious effects on genome stability, more recent research has focused on (potential) functions of G4 structures in telomere maintenance, gene expression, and other cellular processes. The combined research on G4 structures has revealed that properly regulating G4 DNA structures in cells is important to prevent genome instability and disruption of normal cell function. In this short review we provide some background and historical context of our work resulting in the identification of FANCJ, RTEL1 and BLM as helicases that act on G4 structures in vivo. Taken together these studies highlight important roles of different G4 DNA structures and specific G4 helicases at selected genomic locations and telomeres in regulating gene expression and maintaining genome stability.

scholarly journals Mgs1 function at G-quadruplex structures during DNA replication

2020 ◽  
Author(s):  
Katrin Paeschke ◽  
Peter Burkovics
Keyword(s):  
Dna Replication ◽  
Genome Stability ◽  
Mechanistic Model ◽  
Regulation Of Gene Expression ◽  
Telomere Maintenance ◽  
Dna Structures ◽  
Genomic Deletions ◽  
G Quadruplex

AbstractThe coordinated action of DNA polymerases and DNA helicases is essential at genomic sites that are hard to replicate. Among these are sites that harbour G-quadruplex DNA structures (G4). G4s are stable alternative DNA structures, which have been implicated to be involved in important cellular processes like the regulation of gene expression or telomere maintenance. G4 structures were shown to hinder replication fork progression and cause genomic deletions, mutations and recombination events. Many helicases unwind G4 structures and preserve genome stability, but a detailed understanding of G4 replication and the re-start of stalled replication forks around formed G4 structures is not clear, yet. In our recent study, we identified that Mgs1 preferentially binds to G4 DNA structures in vitro and is associated with putative G4-forming chromosomal regions in vivo. Mgs1 binding to G4 motifs in vivo is partially dependent on the helicase Pif1. Pif1 is the major G4-unwinding helicase in S. cerevisiae. In the absence of Mgs1, we determined elevated gross chromosomal rearrangement (GCR) rates in yeast, similar to Pif1 deletion. Here, we highlight the recent findings and set these into context with a new mechanistic model. We propose that Mgs1's functions support DNA replication at G4-forming regions.

scholarly journals The Functional Consequences of Eukaryotic Topoisomerase 1 Interaction with G-Quadruplex DNA

Genes ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 193
Author(s):  
Alexandra Berroyer ◽  
Nayun Kim
Keyword(s):  
Topoisomerase I ◽  
Genome Instability ◽  
Strand Break ◽  
Dna Topology ◽  
Single Strand Break ◽  
Dna Structures ◽  
G4 Dna ◽  
G Quadruplex

Topoisomerase I in eukaryotic cells is an important regulator of DNA topology. Its catalytic function is to remove positive or negative superhelical tension by binding to duplex DNA, creating a reversible single-strand break, and finally religating the broken strand. Proper maintenance of DNA topological homeostasis, in turn, is critically important in the regulation of replication, transcription, DNA repair, and other processes of DNA metabolism. One of the cellular processes regulated by the DNA topology and thus by Topoisomerase I is the formation of non-canonical DNA structures. Non-canonical or non-B DNA structures, including the four-stranded G-quadruplex or G4 DNA, are potentially pathological in that they interfere with replication or transcription, forming hotspots of genome instability. In this review, we first describe the role of Topoisomerase I in reducing the formation of non-canonical nucleic acid structures in the genome. We further discuss the interesting recent discovery that Top1 and Top1 mutants bind to G4 DNA structures in vivo and in vitro and speculate on the possible consequences of these interactions.

scholarly journals Evaluation of Lentiviral-Mediated Expression of Sodium Iodide Symporter in Anaplastic Thyroid Cancer and the Efficacy of In Vivo Imaging and Therapy

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
Chien-Chih Ke ◽  
Ya-Ju Hsieh ◽  
Luen Hwu ◽  
Fu-Hui Wang ◽  
Fu-Du Chen ◽  
...  
Keyword(s):  
Gene Expression ◽  
Sodium Iodide ◽  
Cell Function ◽  
Tumor Imaging ◽  
Promising Result ◽  
Anaplastic Thyroid Cancer ◽  
Anaplastic Thyroid Carcinoma ◽  
Sodium Iodide Symporter

Anaplastic thyroid carcinoma (ATC) is one of the most deadly cancers. With intensive multimodalities of treatment, the survival remains low. ATC is not sensitive to131I therapy due to loss of sodium iodide symporter (NIS) gene expression. We have previously generated a stable human NIS-expressing ATC cell line, ARO, and the ability of iodide accumulation was restored. To make NIS-mediated gene therapy more applicable, this study aimed to establish a lentiviral system for transferring hNIS gene to cells and to evaluate the efficacy of in vitro and in vivo radioiodide accumulation for imaging and therapy. Lentivirus containing hNIS cDNA were produced to transduce ARO cells which do not concentrate iodide. Gene expression, cell function, radioiodide imaging and treatment were evaluated in vitro and in vivo. Results showed that the transduced cells were restored to express hNIS and accumulated higher amount of radioiodide than parental cells. Therapeutic dose of131I effectively inhibited the tumor growth derived from transduced cells as compared to saline-treated mice. Our results suggest that the lentiviral system efficiently transferred and expressed hNIS gene in ATC cells. The transduced cells showed a promising result of tumor imaging and therapy.

scholarly journals The Relevance of G-Quadruplexes for DNA Repair

2021 ◽  
Vol 22 (22) ◽  
pp. 12599
Author(s):  
Rebecca Linke ◽  
Michaela Limmer ◽  
Stefan Juranek ◽  
Annkristin Heine ◽  
Katrin Paeschke
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Genome Stability ◽  
Genome Instability ◽  
Genetic Disorders ◽  
Telomere Maintenance ◽  
Dna Structures ◽  
G4 Dna ◽  
G Quadruplex ◽  
Repair Pathways

DNA molecules can adopt a variety of alternative structures. Among these structures are G-quadruplex DNA structures (G4s), which support cellular function by affecting transcription, translation, and telomere maintenance. These structures can also induce genome instability by stalling replication, increasing DNA damage, and recombination events. G-quadruplex-driven genome instability is connected to tumorigenesis and other genetic disorders. In recent years, the connection between genome stability, DNA repair and G4 formation was further underlined by the identification of multiple DNA repair proteins and ligands which bind and stabilize said G4 structures to block specific DNA repair pathways. The relevance of G4s for different DNA repair pathways is complex and depends on the repair pathway itself. G4 structures can induce DNA damage and block efficient DNA repair, but they can also support the activity and function of certain repair pathways. In this review, we highlight the roles and consequences of G4 DNA structures for DNA repair initiation, processing, and the efficiency of various DNA repair pathways.

scholarly journals E. coli Rep helicase and RecA recombinase unwind G4 DNA and are important for resistance to G4-stabilizing ligands

2020 ◽  
Vol 48 (12) ◽  
pp. 6640-6653 ◽  
Author(s):  
Tapas Paul ◽  
Andrew F Voter ◽  
Rachel R Cueny ◽  
Momčilo Gavrilov ◽  
Taekjip Ha ◽  
...  
Keyword(s):  
Atp Hydrolysis ◽  
Cellular Toxicity ◽  
Dna Structures ◽  
E Coli ◽  
G4 Dna ◽  
G Quadruplex ◽  
Physical Barriers ◽  
Stabilizing Ligands

Abstract G-quadruplex (G4) DNA structures can form physical barriers within the genome that must be unwound to ensure cellular genomic integrity. Here, we report unanticipated roles for the Escherichia coli Rep helicase and RecA recombinase in tolerating toxicity induced by G4-stabilizing ligands in vivo. We demonstrate that Rep and Rep-X (an enhanced version of Rep) display G4 unwinding activities in vitro that are significantly higher than the closely related UvrD helicase. G4 unwinding mediated by Rep involves repetitive cycles of G4 unfolding and refolding fueled by ATP hydrolysis. Rep-X and Rep also dislodge G4-stabilizing ligands, in agreement with our in vivo G4-ligand sensitivity result. We further demonstrate that RecA filaments disrupt G4 structures and remove G4 ligands in vitro, consistent with its role in countering cellular toxicity of G4-stabilizing ligands. Together, our study reveals novel genome caretaking functions for Rep and RecA in resolving deleterious G4 structures.

Growth hormone-induced STAT5B regulates Star gene expression through a cooperation with cJUN in mouse MA-10 Leydig cells

Endocrinology ◽  
2021 ◽  
Author(s):  
Pierre-Olivier Hébert-Mercier ◽  
Francis Bergeron ◽  
Nicholas M Robert ◽  
Samir Mehanovic ◽  
Kenley Joule Pierre ◽  
...  
Keyword(s):  
Gene Expression ◽  
Growth Hormone ◽  
Leydig Cell ◽  
Leydig Cells ◽  
Cell Function ◽  
Mrna Levels ◽  
Leydig Cell Function ◽  
Star Gene

Abstract Leydig cells produce androgens that are essential for male sex differentiation and reproductive function. Leydig cell function is regulated by several hormones and signaling molecules, including growth hormone (GH). Although GH is known to upregulate Star gene expression in Leydig cells, its molecular mechanism of action remains unknown. The STAT5B transcription factor is a downstream effector of GH signaling in other systems. While STAT5B is present in both primary and Leydig cell lines, its function in these cells has yet to be ascertained. Here we report that treatment of MA-10 Leydig cells with GH or overexpression of STAT5B induces Star mRNA levels and increases steroid hormone output. The mouse Star promoter contains a consensus STAT5B element (TTCnnnGAA) at -756 bp to which STAT5B binds in vitro (EMSA and supershift) and in vivo (ChIP) in a GH-induced manner. In functional promoter assays, STAT5B was found to activate a -980 bp mouse Star reporter. Mutating the -756 bp element prevented STAT5B binding but did not abrogate STAT5B-responsiveness. STAT5B was found to functionally cooperate with DNA-bound cJUN. The STAT5B/cJUN cooperation was only observed in Leydig cells and not in Sertoli or fibroblast cells, indicating that additional Leydig cell-enriched transcription factors are required. The STAT5B/cJUN cooperation was lost only when both STAT5B and cJUN elements were mutated. In addition to identifying the Star gene as a novel target for STAT5B in Leydig cells, our data provide important new insights into the mechanism of GH and STAT5B action in the regulation of Leydig cell function.

Abstract 16761: Long Non-coding RNA Meg3 Controls Endothelial Cell Function: Implications for Endothelial Aging and Senescence (Best of Basic Science Abstract)

Circulation ◽  
2015 ◽  
Vol 132 (suppl_3) ◽  
Author(s):  
Reinier Boon ◽  
Patrick Hofmann ◽  
Katharina Michalik ◽  
Andrea Knau ◽  
Yuliya Ponomareva ◽  
...  
Keyword(s):  
Gene Expression ◽  
Endothelial Cells ◽  
Cell Function ◽  
Regulation Of Gene Expression ◽  
Limb Ischemia ◽  
Loss Of Function ◽  
Endothelial Cell Function ◽  
Aged Mice

The majority of transcribed RNA does not encode proteins, but may function as regulatory RNA. Long non-coding RNAs (lncRNAs) have been described to play an important role in many biological processes, including epigenetic regulation of gene expression. To determine the expression and functional role of lncRNAs in endothelial cells, we performed RNA deep sequencing of human umbilical venous endothelial cells (ECs). Among the highest expressed lncRNAs, we identified Meg3 (35.3±0.6 RPKM), which was increased in replicative senescent HUVECs in vitro (passage 16/17 vs 2/3, 2.9±0.99-fold). Interestingly, Meg3 is induced in the intima of aged mice and correlates with age in human hearts (p=0.016). In HUVECs, Meg3 localizes to the nucleus and is also induced by hypoxia (4.08±0.78-fold, p<0.05). Silencing of Meg3 using LNA-GapmeRs induced angiogenic sprouting and proliferation of endothelial cells in vitro (1.4±0.14-fold, P<0.05) and repressed SA-β-galactosidase activity. Conversely, lentiviral overexpression of Meg3 inhibited sprouting angiogenesis and cell cycle progression, although splicing isoforms of Meg3 show differential effects. Mechanistically, RNA immunoprecipitation showed that Meg3 associates specifically to H3K27me3, a silencing chromatin mark, and interacts with EZH2, a histone methyl transferase. Silencing of Meg3 in HUVECs represses, and overexpression of Meg3 induces, global gene expression, as measured by exon array analysis. As Meg3 was described to recruit Jarid2 to chromatin, we determined whether Meg3 requires Jarid2. The Meg3 loss-of-function induced repression of proliferation was normalized after silencing Jarid2, indicating that Meg3 effects are at least partly Jarid2-dependent. Finally, silencing of Meg3 in aged mice in vivo using gapmeRs in combination with hind limb ischemia significantly repressed Meg3 levels in the hindlimb and induced recovery of perfusion compared to control mice. Capillary and arteriole density was also markedly induced after silencing Meg3. These results demonstrate that silencing Meg3 may be a potential strategy to reduce endothelial senescence or increase regenerative angiogenesis.

scholarly journals Disordered region of H3K9 methyltransferase Clr4 binds the nucleosome and contributes to its activity

2019 ◽  
Vol 47 (13) ◽  
pp. 6726-6736 ◽  
Author(s):  
Elias Akoury ◽  
Guoli Ma ◽  
Segolene Demolin ◽  
Cornelia Brönner ◽  
Manuel Zocco ◽  
...  
Keyword(s):  
Gene Expression ◽  
Chromosome Segregation ◽  
Genome Stability ◽  
De Novo ◽  
Regulation Of Gene Expression ◽  
H3k9 Methylation ◽  
Set Domain ◽  
Nucleosome Core

Abstract Heterochromatin is a distinctive chromatin structure that is essential for chromosome segregation, genome stability and regulation of gene expression. H3K9 methylation (H3K9me), a hallmark of heterochromatin, is deposited by the Su(var)3-9 family of proteins; however, the mechanism by which H3K9 methyltransferases bind and methylate the nucleosome is poorly understood. In this work we determined the interaction of Clr4, the fission yeast H3K9 methyltransferase, with nucleosomes using nuclear magnetic resonance, biochemical and genetic assays. Our study shows that the Clr4 chromodomain binds the H3K9me3 tail and that both, the chromodomain and the disordered region connecting the chromodomain and the SET domain, bind the nucleosome core. We show that interaction of the disordered region with the nucleosome core is independent of H3K9me and contributes to H3K9me in vitro and in vivo. Moreover, we show that those interactions with the nucleosome core are contributing to de novo deposition of H3K9me and to establishment of heterochromatin.

scholarly journals Effects of gypenosides on enteroendocrine L-cell function and GLP-1 secretion

2020 ◽  
Author(s):  
Chinmai Patibandla ◽  
Erin Campbell ◽  
Xinhua Shu ◽  
Angus M Shaw ◽  
Sharron Dolan ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Function ◽  
Postprandial Glucose ◽  
Prohormone Convertase ◽  
Antioxidant Gene ◽  
Protein Levels ◽  
L Cells ◽  
Prohormone Convertase 2

AbstractGlucagon-like peptide 1 (GLP-1) is an incretin hormone produced in gut L-cells, which regulates postprandial glucose-dependent insulin secretion, also known as the incretin effect. GLP-1 secretion may be reduced in type 2 diabetes mellitus, impacting on glycaemic regulation. Thus, methods to enhance endogenous GLP-1 secretion by use of natural GLP-1 secretagogues may improve glucose control in diabetes. Gypenosides (GYP) extracted from the plant Gynostemma Pentaphyllum (Jiaogulan) are known for their glucose-lowering effects both in vitro and in vivo, although their effect on GLP-1 secretion is unknown. Our results showed that GYP enhanced cell viability and significantly upregulated antioxidant gene Nrf2, Cat and Ho-1 expression. GYP did not affect glucokinase expression but downregulated proglucagon gene expression over 24h, although, cellular GLP-1 content was unchanged. Prohormone convertase 1 (Pcsk1) gene expression was unchanged by GYP over 24h, although protein levels were significantly downregulated, while prohormone convertase 2 (Pcsk2) mRNA and protein levels were significantly upregulated. Acute exposure to gypenosides enhanced calcium uptake and GLP-1 release from GLUTag cells both at low and high glucose concentrations. These results suggest that anti-diabetic properties of gypenosides are partly linked to their ability to stimulate GLP-1 secretion. Gypenosides enhance antioxidant gene expression and may protect L-cells from excess oxidative stress.

scholarly journals G-quadruplex RNA motifs influence gene expression in the malaria parasite Plasmodium falciparum

2021 ◽  
Author(s):  
Franck Dumetz ◽  
Eugene Yui-Ching Chow ◽  
Lynne M. Harris ◽  
Mubarak I. Umar ◽  
Anders Jensen ◽  
...  
Keyword(s):  
Gene Expression ◽  
Plasmodium Falciparum ◽  
Malaria Parasite ◽  
Regulation Of Gene Expression ◽  
Low Complexity ◽  
Telomere Maintenance ◽  
Translation Efficiency ◽  
G Quadruplex

ABSTRACTG-quadruplexes are non-helical secondary structures that can fold in vivo in both DNA and RNA. In human cells, they can influence replication, transcription and telomere maintenance in DNA, or translation, transcript processing and stability of RNA. We have previously showed that G-quadruplexes are detectable in the DNA of the malaria parasite Plasmodium falciparum, despite a very highly A/T-biased genome with unusually few guanine-rich sequences. Here, we show that RNA G-quadruplexes can also form in P. falciparum RNA, using rG4-seq for transcriptome-wide structure-specific RNA probing. Many of the motifs, detected here via the rG4seeker pipeline, have non-canonical forms and would not be predicted by standard in silico algorithms. However, in vitro biophysical assays verified the formation of non-canonical motifs. The G-quadruplexes in the P. falciparum transcriptome are frequently clustered in certain genes and associated with regions encoding low-complexity peptide repeats. They are overrepresented in particular classes of genes, notably those that encode PfEMP1 virulence factors, stress response genes and DNA binding proteins. In vitro translation experiments and in vivo measures of translation efficiency showed that G-quadruplexes can influence the translation of P. falciparum mRNAs. Thus, the G-quadruplex is a novel player in post-transcriptional regulation of gene expression in this major human pathogen.

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