Regulator Of Telomere Elongation Research Articles

Individual Differences in Relative Telomere Length in Mentally Healthy Subjects: The Effect of TERT Gene Polymorphism and Urban Residency.

The changes in the telomere length caused by the terminal underreplication in the existing literature are related to depressive disorders. However, the use of the telomere length as a biomarker of depressive states is ambiguous, which is due to the effect of various environmental factors on both the psychoemotional state and cellular aging of an organism. In order to identify the possible use of the relative telomere length (RTL) measured in peripheral blood leukocytes as a biomarker of enhanced liability to depression prior to the clinical symptoms, as well as to determine the link between telomere length, sociodemographic factors, allelic variants of the genes involved in the regulation of telomere elongation, and depression level, the association analysis of reverse transcriptase (TERT rs7726159), telomerase RNA component (TERC rs1317082), and the CST complex encoding protein (OBFC1 rs2487999) gene polymorphisms was performed with RTL and depression level in mentally healthy individuals (N = 1065) aged 18–25 years. Together with genetic variants, the examined regression models included various sociodemographic parameters as predictors. As a result of statistical analysis, we failed to observe the association between RTL and individual differences in depression level in the studied sample. Nevertheless, multiple regression analysis allowed us to construct a statistically significant model of individual variance in RTL (P = 4.3е–4; r2 = 0.018), which included rs7726159 in the TERT gene (P = 0.020; β = 0.078) and such environmental predictors as age (P = 0.001; β = –0.027) and place of residence in childhood (urban/rural area) (P = 0.048; β = 0.063). The data obtained confirm the involvement of TERT gene variants and age in telomere length in mentally healthy individuals aged 18–25 years and indicate a negative effect of urban residency on telomere length shortening, which reflects the cellular aging of an organism.

A resonance Rayleigh scattering sensor for sensitive differentiation of telomere DNA length and monitoring special motifs (G-quadruplex and i-motif) based on the Ag nanoclusters and NAND logic gate responding to chemical input signals

BackgroundDifferentiation of telomere length is of vital importance because telomere length is closely related with several deadly diseases such as cancer. Additionally, G-quadruplex and i-motif formation in telomeric DNA have been shown to act as a negative regulator of telomere elongation by telomerase in vivo and are considered as an attractive drug target for cancer chemotherapy.ResultsIn this assay, Ag nanoclusters templated by hyperbranched polyethyleneimine (PEI–Ag NCs) are designed as a new novel resonance Rayleigh scattering (RRS) probe for sensitive differentiation of telomere length and monitoring special motifs (G-quadruplex and i-motif). In this assay, free PEI–Ag NC probe or DNA sequence alone emits low intensities of RRS, while the formation of PEI–Ag NCs/DNA complexes yields greatly enhanced RRS signals; however, when PEI–Ag NCs react with G-quadruplex or i-motif, the intensities of RRS exhibit slight changes. At the same concentration, the enhancement of RRS signal is directly proportional to the length of telomere, and the sensitivity of 64 bases is the highest with the linear range of 0.3–50 nM (limit of detection 0.12 nM). On the other hand, due to the conversion of telomere DNA molecules among multiple surrounding conditions, a DNA logic gate is developed on the basis of two chemical input signals (K+ and H+) and a change in RRS intensity as the output signal.ConclusionOur results indicate that PEI–Ag NCs can serve as a novel RRS probe to identify DNA length and monitor G-quadruplex/i-motif through the different increasing degrees of RRS intensity. Meanwhile, the novel attributes of the nanoprobe stand superior to those involving dyes or labeled DNA because of no chemical modification, low cost, green, and high efficiency.

ZSCAN4 and TRF1: A functionally indirect interaction in cancer cells independent of telomerase activity

PurposeRecently, the newly identified embryonic stem cell marker, Zinc finger and SCAN domain containing 4 gene (ZSCAN4), which plays a key role in genomic stability by regulating telomere elongation, was shown to co-localize with TRF1 foci. This suggests that the interaction of ZSCAN4 with TRF1 functions in regulation of telomere elongation in ESC. Based on these studies, we hypothesized that ZSCAN4 binds to TRF1 in cancer cells to function in regulating telomere length. The purpose of this study was to determine whether this interaction occurred across different cell lineage-derived cancers and whether telomerase status impacted this relationship. To that end, telomerase positive cervical cancer cells (HeLa) and breast cancer cells (MCF7), and telomerase negative osteosarcoma cells (SaOS2), were analyzed for ZSCAN4 and TRF1 interactions. ResultsImmunocytochemistry demonstrated co-localization of ZSCAN4 and TRF1 to the nucleus. This functional relationship was confirmed using BiFC imaging analysis based on distance in situ. Co-immunoprecipitation and pull-down assay results demonstrated that ZSCAN4 binds with TRF1 in vitro indirectly. All three cell types showed similar results. ConclusionsIn this study, we revealed, for the first time, that ZSCAN4 indirectly interacts with TRF1 (functional association protein) in cancer cells. Furthermore, we show that ZSCAN4 plays an important role independent of telomere maintenance pathways (telomerase positive and ALT) or cell lineage.

Roles for Histone Acetylation in Regulation of Telomere Elongation and Two-cell State in Mouse ES Cells.

Mammalian telomeres and subtelomeres are marked by heterochromatic epigenetic modifications, including repressive DNA methylation and histone methylation (e.g., H3K9me3 and H4K20me3). Loss of these epigenetic marks results in increased rates of telomere recombination and elongation. Other than these repressive epigenetic marks, telomeric and subtelomeric H3 and H4 are underacetylated. Yet, whether histone acetylation also regulates telomere length has not been directly addressed. We thought to test the effects of histone acetylation levels on telomere length using histone deacetylase (HDAC) inhibitor (sodium butyrate, NaB) that mediates histone hyperacetylation and histone acetyltransferase (HAT) inhibitor (C646) that mediates histone hypoacetylation. We show that histone hyperacetylation dramatically elongates telomeres in wild-type ES cells, and only slightly elongates telomeres in Terc(-/-) ES cells, suggesting that Terc is involved in histone acetylation-induced telomere elongation. In contrast, histone hypoacetylation shortens telomeres in both wild-type and Terc(-/-) ES cells. Additionally, histone hyperacetylation activates 2-cell (2C) specific genes including Zscan4, which is involved in telomere recombination and elongation, whereas histone hypoacetylation represses Zscan4 and 2C genes. These data suggest that histone acetylation levels affect the heterochromatic state at telomeres and subtelomeres, and regulate gene expression at subtelomeres, linking histone acetylation to telomere length maintenance.

Abstract 579: The interaction of ZSCAN4 with TRF1: effects on regulation of telomere elongation in cancer cells.

Abstract Telomeres are repetitive sequences at the ends of chromosomes protected by DNA binding proteins of shelterin complex that form capping structures. One of these proteins, TRF1, plays a role in the regulation of telomere length through its interaction with other proteins in the shelterin complex. High levels of TRF1 expression have been shown to accelerate telomere shortening, whereas dominant-negative inhibition of TRF1 leads to telomere elongation. Recently, the newly identified Zinc finger and SCAN domain containing4 gene (ZSCAN4) plays a key role in genomic stability by regulating telomere elongation and was shown to co-localize with TRF1 foci in mouse embryonic stem cell. Here, we show that ZSCAN4 is a TRF1 association protein in breast cancer cells. We hypothesized that ZSCAN4 would affect levels of TRF1expression and correspondingly control the function of TRF1 through negative regulation and dominant-negative inhibition. Using Co-immunoprecipitation and TNT Pull-down assay, we demonstrate that ZSCAN4 binds with TRF1 in vitro. Localization and visualization of interacting protein-protein interactions in living cells are crucial to elucidate between TRF1 and ZSCAN4. Using a bimolecular fluorescence complementation (BiFC) assay, we show the directly visualize TRF1 and ZSCAN4 interactions in living cells. Using telomere length assays, we demonstrate that ZSCAN4 is an association protein of TRF1 to regulate telomere and affect in the telomere elongation of cancer. The ZSCAN4 mediated cooperative binding of TRF1 to telomeric DNA has important implications for understanding the mechanism of telomere extension. Citation Format: kyungwoo lee. The interaction of ZSCAN4 with TRF1: effects on regulation of telomere elongation in cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 579. doi:10.1158/1538-7445.AM2013-579

Abstract 2047: The interaction of ZSCAN4 with TRF1: Effects on regulation of telomere elongation in cancer cells

Abstract Telomeres are repetitive sequences at the ends of chromosomes protected by DNA binding proteins of shelterin complex that form capping structures. One of these proteins, TRF1, plays a role in the regulation of telomere length through its interaction with other proteins in the shelterin complex. High levels of TRF1 expression have been shown to accelerate telomere shortening, whereas dominant-negative inhibition of TRF1 leads to telomere elongation. Recently, the newly identified Zinc finger and SCAN domain containing4 gene (ZSCAN4) plays a key role in genomic stability by regulating telomere elongation and was shown to co-localize with TRF1 foci. Here, we show that ZSCAN4 is a TRF1 association protein. We hypothesized that ZSCAN4 would affect levels of TRF1expression and correspondingly control the function of TRF1 through negative regulation and dominant-negative inhibition. Using Co-immunoprecipitation, we demonstrate that ZSCAN4 binds with TRF1 in vitro. Pull-down assay results show that ZSCAN4 directly interacts with TRF1. Using PCR mutagenesis, we have identified the binding site between ZSCAN4 and TRF1. Furthermore, over-expression of ZSCAN4 expression acts as an activator of telomere elongation. The ZSCAN4 mediated cooperative binding of TRF1 to telomeric DNA has important implications for understanding the mechanism of telomere extension. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2047. doi:1538-7445.AM2012-2047

γH2A is a component of yeast heterochromatin required for telomere elongation

Histones of heterochromatin are deacetylated in yeast and methylated in more complex eukaryotes to regulate heterochromatin structure and gene silencing. Here, we report that histone H2A phosphorylated at serine 129 (γH2A) in Saccharomyces cerevisiae is a conceptually new type of heterochromatin modification that functions downstream of silent chromatin assembly. We show that γH2A is enriched throughout yeast telomeric and silent mating locus (HM) heterochromatin where γH2A results from the action of kinases Tel1 and Mec1. Interestingly, mutation of γH2A has no apparent effect on the binding of Sir (silent information regulator) complex or on gene silencing. In contrast, deletion of SIR3 abolishes the formation of γH2A at heterochromatin. To address the function of γH2A, we used a Δrif1 mutant strain in which telomeres are excessively elongated to show that γH2A is required for the optimal recruitment of Cdc13, a regulator of telomere elongation, and for telomere elongation itself. Thus, a histone modification that parallels Sir3 protein binding is shown here to be dispensable for the formation of a silent structure but is important for a crucial heterochromatin-specific downstream function in telomere homeostasis.

Crystal structure of the PIN domain of human telomerase‐associated protein EST1A

Saccharomyces cerevisiae Est1p is a telomerase-associated protein essential for telomere length homeostasis. hEST1A is one of the three human Est1p homologues and is considered to be involved not only in regulation of telomere elongation or capping but also in nonsense-mediated degradation of RNA. hEST1A is composed of two conserved regions, Est1p homology and PIN (PilT N-terminus) domains. The present study shows the crystal structure of the PIN domain at 1.8 A resolution. The overall structure is composed of an alpha/beta fold or a core structure similar to the counterpart of 5' nucleases and an extended structure absent from archaeal PIN-domain proteins and 5' nucleases. The structural properties of the PIN domain indicate its putative active center consisting of invariant acidic amino acid residues, which is geometrically similar to the active center of 5' nucleases and an archaeal PAE2754 PIN-domain protein associated with exonuclease activity.

Telomeres on the Cdk roller-coaster ride

Each round of DNA replication results in the erosion of telomeres, the ends of linear chromosomes. Telomerase counteracts telomere shortening by synthesizing new DNA sequences in a time period restricted to late S a d G2 cell-cycle phases, even though the enzyme is active throughout the cell cycle. A recent study directly implicates cyclin dependent kinase (Cdk1) in the regulation of telomere elongation during the cell cycle.

Regulation of Telomere Elongation by the Cyclin-Dependent Kinase CDK1

Telomere elongation is cell-cycle regulated and requires the coordinated activity of proteins involved in the DNA damage response. We used an assay that detects de novo telomere addition to examine the role of the cyclin-dependent kinase Cdk1 (Cdc28) in cell-cycle-specific telomere elongation. Inhibition of an ATP analog-sensitive allele of Cdk1 completely blocked the addition of telomere repeats. Mutations in Rif2 and DNA polymerase alpha that cause increased telomere elongation were unable to compensate for the loss of Cdk1 activity, suggesting Cdk1 activity is required for an early step in telomere addition. Mutations in DNA repair proteins that act with Cdk1 at double-strand breaks also prevented telomere elongation. Cdk1 activity was required for the generation of 3' single-strand overhangs at both native and de novo telomeres. We propose Cdk1 activity controls the timing of telomere elongation by regulating the single-strand overhang at chromosome ends.

A cellular survival switch: poly(ADP-ribosyl)ation stimulates DNA repair and silences transcription.

Poly(ADP-ribosyl)ation is a post-translational modification occurring in the nucleus. The most abundant and best-characterized enzyme catalyzing this reaction, poly(ADP-ribose) polymerase 1 (PARP1), participates in fundamental nuclear events. The enzyme functions as molecular "nick sensor". It binds with high affinity to DNA single-strand breaks resulting in the initiation of its catalytic activity. Activated PARP1 promotes base excision repair. In addition, PARP1 modifies several transcription factors and thereby precludes their binding to DNA. We propose that a major function of PARP1 includes the silencing of transcription preventing expression of damaged genes. Concomitant stimulation of DNA repair suggests that PARP1 acts as a switch between transcription and DNA repair. Another PARP-type enzyme, tankyrase, is involved in the regulation of telomere elongation. Tankyrase modifies a telomere-associated protein and thereby prevents it masking telomeric repeats providing access of telomerase for telomere elongation. Therefore, poly(ADP-ribosyl)ation reactions may act as molecular switches in DNA metabolism.