BACKGROUND: Telomeres are protective structures at chromosome ends which shorten gradually with increasing age. In chronic lymphocytic leukemia (CLL), short telomeres have been associated with unfavorable disease outcome, but the link between clonal evolution and telomere shortening remains unresolved. METHODS: We investigated relative telomere length (RTL) in a well-characterized cohort of 198 CLL patients by qPCR and focused in detail on a subgroup 26 patients who underwent clonal evolution of TP53 mutations (evolTP53). In the evolTP53 subgroup we explored factors influencing clonal evolution and corresponding changes in telomere length through measurements of telomerase expression, lymphocyte doubling time, and BCR signaling activity. RESULTS: At baseline, RTL of the evolTP53 patients was scattered across the entire RTL spectrum observed in our CLL cohort. RTL changed in the follow-up samples of 16/26 (62%) evolTP53 cases, inclining to reach intermediate RTL values, i.e., longer telomeres shortened compared to baseline while shorter ones prolonged. For the first time we show that TP53 clonal shifts are linked to RTL change, including unexpected RTL prolongation. We further investigated parameters associated with RTL changes. Unstable telomeres were significantly more frequent among younger patients (P = 0.032). Shorter telomeres were associated with decreased activity of the B-cell receptor signaling components p-ERK1/2, p-ZAP-70/SYK, and p-NFκB (P = 0.04, P = 0.01, and P = 0.02, respectively). CONCLUSIONS: Our study revealed that changes of telomere length reflect evolution in leukemic subclone proportion, and are associated with specific clinico-biological features of the explored cohort.
- MeSH
- Leukemia, Lymphocytic, Chronic, B-Cell genetics MeSH
- Clonal Evolution genetics MeSH
- Middle Aged MeSH
- Humans MeSH
- Mutation MeSH
- Tumor Suppressor Protein p53 genetics MeSH
- Proto-Oncogene Proteins c-bcr metabolism MeSH
- Signal Transduction MeSH
- Telomerase genetics MeSH
- Telomere ultrastructure MeSH
- Check Tag
- Middle Aged MeSH
- Humans MeSH
- Male MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
Chromosome pairing in meiosis usually starts in the vicinity of the telomere attachment to the nuclear membrane and congregation of telomeres in the leptotene bouquet is believed responsible for bringing homologue pairs together. In a heterozygote for an inversion of a rye (Secale cereale L.) chromosome arm in wheat, a distal segment of the normal homologue is capable of chiasmate pairing with its counterpart in the inverted arm, located near the centromere. Using 3D imaging confocal microscopy, we observed that some telomeres failed to be incorporated into the bouquet and occupied various positions throughout the entire volume of the nucleus, including the centromere pole. Rye telomeres appeared ca. 21 times more likely to fail to be included in the telomere bouquet than wheat telomeres. The frequency of the out-of-bouquet rye telomere position in leptotene was virtually identical to the frequency of telomeres deviating from Rabl's orientation in the nuclei of somatic cells, and was similar to the frequency of synapsis of the normal and inverted chromosome arms, but lower than the MI pairing frequency of segments of these two arms normally positioned across the volume of the nucleus. Out-of-position placement of the rye telomeres may be responsible for reduced MI pairing of rye chromosomes in hybrids with wheat and their disproportionate contribution to aneuploidy, but appears responsible for initiating chiasmate pairing of distantly positioned segments of homology in an inversion heterozygote.
- MeSH
- Cell Nucleus genetics ultrastructure MeSH
- Centromere chemistry ultrastructure MeSH
- Chimera genetics MeSH
- Chromosome Inversion * MeSH
- Chromosomes, Plant chemistry ultrastructure MeSH
- Species Specificity MeSH
- Heterozygote MeSH
- In Situ Hybridization, Fluorescence MeSH
- Microscopy, Confocal MeSH
- Chromosome Pairing MeSH
- Image Processing, Computer-Assisted statistics & numerical data MeSH
- Meiotic Prophase I * MeSH
- Triticum genetics ultrastructure MeSH
- Plant Cells metabolism ultrastructure MeSH
- Telomere chemistry ultrastructure MeSH
- Secale genetics ultrastructure MeSH
- Imaging, Three-Dimensional methods MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
Ionizing radiation produces clustered damage to DNA which is difficult to repair and thus more harmful than single lesions. Clustered lesions have only been investigated in dsDNA models. Introducing the term 'clustered damage to G-quadruplexes' we report here on the structural effects of multiple tetrahydrofuranyl abasic sites replacing loop adenines (A/AP) and tetrad guanines (G/AP) in quadruplexes formed by the human telomere d[AG3(TTAG3)3] (htel-22) and d[TAG3(TTAG3)3TT] (htel-25) in K+ solutions. Single to triple A/APs increased the population of parallel strands in their structures by stabilizing propeller type loops, shifting the antiparallel htel-22 into hybrid or parallel quadruplexes. In htel-25, the G/APs inhibited the formation of parallel strands and these adopted antiparallel topologies. Clustered G/AP and A/APs reduced the thermal stability of the wild-type htel-25. Depending on position, A/APs diminished or intensified the damaging effect of the G/APs. Taken together, clustered lesions can disrupt the topology and stability of the htel quadruplexes and restrict their conformational space. These in vitro results suggest that formation of clustered lesions in the chromosome capping structure can result in the unfolding of existing G-quadruplexes which can lead to telomere shortening.
- MeSH
- Adenine chemistry MeSH
- Circular Dichroism MeSH
- DNA chemistry genetics MeSH
- Furans chemistry MeSH
- G-Quadruplexes * MeSH
- Humans MeSH
- Models, Molecular MeSH
- Nuclear Magnetic Resonance, Biomolecular MeSH
- Oligonucleotides chemistry MeSH
- Solutions MeSH
- Telomere genetics ultrastructure MeSH
- Telomere Shortening * MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- MeSH
- Survival Analysis MeSH
- Ataxia Telangiectasia Mutated Proteins genetics MeSH
- Leukemia, Lymphocytic, Chronic, B-Cell classification genetics mortality MeSH
- Cohort Studies MeSH
- Humans MeSH
- Mutation * MeSH
- Sequence Analysis, DNA MeSH
- Telomere ultrastructure MeSH
- Telomere Shortening * MeSH
- Check Tag
- Humans MeSH
- Publication type
- Letter MeSH
- Multicenter Study MeSH
- Research Support, Non-U.S. Gov't MeSH
Telomeres of nuclear chromosomes are usually composed of an array of tandemly repeated sequences that are recognized by specific Myb domain containing DNA-binding proteins (telomere-binding proteins, TBPs). Whereas in many eukaryotes the length and sequence of the telomeric repeat is relatively conserved, telomeric sequences in various yeasts are highly variable. Schizosaccharomyces pombe provides an excellent model for investigation of co-evolution of telomeres and TBPs. First, telomeric repeats of S. pombe differ from the canonical mammalian type TTAGGG sequence. Second, S. pombe telomeres exhibit a high degree of intratelomeric heterogeneity. Third, S. pombe contains all types of known TBPs (Rap1p [a version unable to bind DNA], Tay1p/Teb1p, and Taz1p) that are employed by various yeast species to protect their telomeres. With the aim of reconstructing evolutionary paths leading to a separation of roles between Teb1p and Taz1p, we performed a comparative analysis of the DNA-binding properties of both proteins using combined qualitative and quantitative biochemical approaches. Visualization of DNA-protein complexes by electron microscopy revealed qualitative differences of binding of Teb1p and Taz1p to mammalian type and fission yeast telomeres. Fluorescence anisotropy analysis quantified the binding affinity of Teb1p and Taz1p to three different DNA substrates. Additionally, we carried out electrophoretic mobility shift assays using mammalian type telomeres and native substrates (telomeric repeats, histone-box sequences) as well as their mutated versions. We observed relative DNA sequence binding flexibility of Taz1p and higher binding stringency of Teb1p when both proteins were compared directly to each other. These properties may have driven replacement of Teb1p by Taz1p as the TBP in fission yeast.
- MeSH
- DNA-Binding Proteins genetics metabolism ultrastructure MeSH
- Microscopy, Electron MeSH
- Fluorescence Polarization MeSH
- Phylogeny MeSH
- Genetic Variation MeSH
- Humans MeSH
- Evolution, Molecular MeSH
- Oligonucleotides genetics metabolism MeSH
- Telomere-Binding Proteins classification genetics metabolism ultrastructure MeSH
- Electrophoretic Mobility Shift Assay MeSH
- Schizosaccharomyces pombe Proteins genetics metabolism ultrastructure MeSH
- Schizosaccharomyces genetics MeSH
- Base Sequence MeSH
- Telomere genetics metabolism ultrastructure MeSH
- Transcription Factors genetics metabolism ultrastructure MeSH
- Protein Binding MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Research Support, N.I.H., Extramural MeSH
A new repeated DNA from Microtus thomasi, Mth-Alu2.2, was cloned and characterized and is presented here for the first time. Digestion of genomic DNA from M. thomasi with AluI restriction enzyme revealed a 2.2-kb repetitive DNA sequence with a high AT content (69%). This sequence consists of a tandemly repeated nonanucleotide of the consensus sequence CACAATGTA, which constitutes approximately 93-95% of the total unit length. The location of the Mth-Alu2.2 sequence in the karyotype was determined by FISH, demonstrating strong hybridization signals in the pericentromeric regions of all chromosomes and in the heterochromatin blocks of several X chromosome variants. In addition, the distribution of the 4 pericentromeric repeat sequences Msat-160, Mth-Alu900, Mth-Alu2.2, and interstitial telomeric repeats was analyzed by in situ hybridization in M. thomasi, in order to shed light on the complex composition of the chromosomal pericentromeric regions in this species. The order and organization of these sequences in the pericentromeric regions are conserved, with slight variations in both the degree of overlapping and the amount of each repeated DNA in the chromosomes. Specifically, Mth-Alu2.2 is localized in the terminal regions of the chromosomes, with Msat-160 occupying the immediately inner region, partially intermixed with Mth-Alu2.2. The sequence Mth-Alu900 is found in internal positions below Msat-160, and the interstitial telomeric repeats are located close to the long-arm euchromatin of the chromosomes.
- MeSH
- Arvicolinae genetics metabolism MeSH
- Cell Lineage MeSH
- Centromere ultrastructure MeSH
- Centrosome ultrastructure MeSH
- DNA chemistry MeSH
- Phenotype MeSH
- Heterochromatin chemistry MeSH
- In Situ Hybridization, Fluorescence MeSH
- Karyotyping MeSH
- Crosses, Genetic MeSH
- Repetitive Sequences, Nucleic Acid MeSH
- Telomere ultrastructure MeSH
- Animals MeSH
- Check Tag
- Male MeSH
- Female MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Recent findings suggest that apoptotic protein apoptosis-inducing factor (AIF) may also play an important non-apoptotic function inside mitochondria. AIF was proposed to be an important component of respiratory chain complex I that is the major producer of superoxide radical. The possible role of AIF is still controversial. Superoxide production could be used as a valuable measure of complex I function, because the majority of superoxide is produced there. Therefore, we employed superoxide-specific mitochondrial fluorescence dye for detection of superoxide production. We studied an impact of AIF knockdown on function of mitochondrial complex I by analyzing superoxide production in selected cell lines. Our results show that tumoral telomerase-positive (TP) AIF knockdown cell lines display significant increase in superoxide production in comparison to control cells, while a non-tumoral cell line and tumoral telomerase-negative cell lines with alternative lengthening of telomeres (ALT) show a decrease in superoxide production. According to these results, we can conclude that AIF knockdown disrupts function of complex I and therefore increases the superoxide production in mitochondria. The distinct effect of AIF depletion in various cell lines could result from recently discovered activity of telomerase in mitochondria of TP cancer cells, but this hypothesis needs further investigation.
- MeSH
- Cell Line MeSH
- Apoptosis Inducing Factor genetics physiology MeSH
- Phenanthridines pharmacology MeSH
- Fluorescent Dyes pharmacology MeSH
- HeLa Cells MeSH
- Humans MeSH
- Mitochondrial Membranes metabolism MeSH
- Mitochondria metabolism MeSH
- Cell Line, Tumor MeSH
- Image Processing, Computer-Assisted MeSH
- Electron Transport Complex I metabolism MeSH
- Superoxides metabolism MeSH
- Telomerase metabolism MeSH
- Telomere ultrastructure MeSH
- Gene Silencing MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Účel prehľadu: Z posledných výskumov vyplýva, že chronická obštrukčná choroba pľúc (CHOCHP) môže byť ochorením zrýchleného starnutia. Hypotézu starnutia a patogenézy CHOCHP podporujú štúdie in vitro, in vivo a klinické štúdie. Účelom tohto prehľadu je podať komplexný prehľad o hypotéze starnutia pri CHOCHP a zhrnúť metódy, ktoré sa používajú na hodnotenie starnutia buniek. Nové poznatky: Predpokladá sa, že zrýchlené starnutie v dôsledku expozície cigaretovému dymu vyvoláva rýchlu progresiu CHOCHP. Podľa výsledkov posledných štúdií majú pacienti s CHOCHP v porovnaní so zdravými kontrolnými osobami zvýšenú expresiu proteínov spojených so starnutím v pľúcach aj v periférnom obehu. Na zvieracích modeloch zrýchleného starnutia boli potvrdené spontánne emfyzematózne zmeny v pľúcach. V pľúcach pacientov s CHOCHP sa zasa zistila zvýšená koncentrácia markerov starnutia vo fibroblastoch a v alveolárnych bunkách. Posledné štúdie telomér, ktoré sa skracujú so starnutím buniek, ukázali, že u pacientov s CHOCHP môže v porovnaní so zdravými kontrolnými osobami dochádzať k zrýchlenému skracovaniu telomér. Doterajšie štúdie sú však pomerne malé a poskytujú rôznorodé výsledky. Súhrn: Nachádzame čoraz viac dôkazov o úlohe zrýchleného procesu starnutia v progresii CHOCHP. Starnutie je jedným z možných molekulárnych pochodov, pri ktorom vzniká CHOCHP.
Recent research suggests that chronic obstructive pulmonary disease (COPD) may be a disease of accelerated aging. The senescence hypothesis of COPD pathogenesis is supported by in-vitro, in-vivo and clinical studies. The purpose of this review is to provide a comprehensive overview of the senescence hypothesis of COPD and summarize methods that are used to assess cellular aging. RECENT FINDINGS: Accelerated aging due to exposure to cigarette smoke is hypothesized to induce rapid progression of COPD. Recent studies have shown that COPD patients have enhanced expression of senescence-associated proteins in the lung and in the peripheral circulation compared to healthy controls. Murine models of accelerated aging demonstrate spontaneous emphysematous changes in the lungs, while lungs of COPD patients demonstrate enhanced markers of senescence in fibroblasts and alveolar cells. More recently, studies of telomeres, which shorten with cellular aging, have shown that COPD patients may experience accelerated telomere attrition compared with healthy controls. However, studies to date have been relatively small and have produced heterogeneous results. SUMMARY: The evidence for the role of accelerated aging in COPD progression is growing and senescence is one possible molecular pathway by which COPD occurs.
- MeSH
- Biomarkers chemistry MeSH
- Pulmonary Disease, Chronic Obstructive etiology physiopathology MeSH
- Financing, Organized MeSH
- In Situ Hybridization, Fluorescence MeSH
- Leukocytes physiology MeSH
- Humans MeSH
- Oxidative Stress physiology MeSH
- Polymerase Chain Reaction MeSH
- Disease Progression MeSH
- Blotting, Southern MeSH
- Cellular Senescence physiology MeSH
- Aging physiology MeSH
- Telomere physiology ultrastructure MeSH
- Check Tag
- Humans MeSH
- Publication type
- Review MeSH
The organisation of dinoflagellate chromosomes is exceptional among eukaryotes. Their genomes are the largest in the Eukarya domain, chromosomes lack histones and may exist in liquid crystalline state. Therefore, the study of the structural and functional properties of dinoflagellate chromosomes is of high interest. In this work, we have analysed the telomeres and telomerase in two Dinoflagellata species, Karenia papilionacea and Crypthecodinium cohnii. Active telomerase, synthesising exclusively Arabidopsis-type telomere sequences, was detected in cell extracts. The terminal position of TTTAGGG repeats was determined by in situ hybridisation and BAL31 digestion methods and provides evidence for the linear characteristic of dinoflagellate chromosomes. The length of telomeric tracts, 25-80 kb, is the largest among unicellular eukaryotic organisms to date. Both the presence of long arrays of perfect telomeric repeats at the ends of dinoflagellate chromosomes and the existence of active telomerase as the primary tool for their high-fidelity maintenance demonstrate the general importance of these structures throughout eukaryotes. We conclude that whilst chromosomes of dinoflagellates are unique in many aspects of their structure and composition, their telomere maintenance follows the most common scenario.
- MeSH
- Chromatin genetics metabolism MeSH
- Chromosomes genetics metabolism ultrastructure MeSH
- Dinoflagellida genetics growth & development metabolism ultrastructure MeSH
- Liquid Crystals MeSH
- DNA, Protozoan genetics MeSH
- Repetitive Sequences, Nucleic Acid MeSH
- DNA Replication genetics MeSH
- Telomerase metabolism MeSH
- Telomere genetics metabolism ultrastructure MeSH
- DNA Breaks MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
