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.

• Klíčová slova
• BCR signaling, Chronic Lymphocytic Leukemia, Clonal evolution, TP53, Telomere,
• MeSH
• chronická lymfatická leukemie genetika   MeSH
• klonální evoluce genetika   MeSH
• lidé středního věku MeSH
• lidé MeSH
• mutace MeSH
• nádorový supresorový protein p53 genetika   MeSH
• protoonkogenní proteiny c-bcr metabolismus   MeSH
• signální transdukce MeSH
• telomerasa genetika   MeSH
• telomery ultrastruktura   MeSH
• Check Tag
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• nádorový supresorový protein p53 MeSH
• protoonkogenní proteiny c-bcr MeSH
• telomerasa MeSH
• TP53 protein, human MeSH Prohlížeč

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.

• Klíčová slova
• 3D FISH, Centromere, Leptotene bouquet, Pairing initiation, Telomere,
• MeSH
• buněčné jádro genetika   ultrastruktura   MeSH
• centromera chemie   ultrastruktura   MeSH
• chiméra genetika   MeSH
• chromozomální inverze * MeSH
• chromozomy rostlin chemie   ultrastruktura   MeSH
• druhová specificita MeSH
• heterozygot MeSH
• hybridizace in situ fluorescenční MeSH
• konfokální mikroskopie MeSH
• párování chromozomů MeSH
• počítačové zpracování obrazu statistika a číselné údaje   MeSH
• profáze meiózy I * MeSH
• pšenice genetika   ultrastruktura   MeSH
• rostlinné buňky metabolismus   ultrastruktura   MeSH
• telomery chemie   ultrastruktura   MeSH
• žito genetika   ultrastruktura   MeSH
• zobrazování trojrozměrné metody   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem 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
• adenin chemie   MeSH
• cirkulární dichroismus MeSH
• DNA chemie   genetika   MeSH
• furany chemie   MeSH
• G-kvadruplexy * MeSH
• lidé MeSH
• molekulární modely MeSH
• nukleární magnetická rezonance biomolekulární MeSH
• oligonukleotidy chemie   MeSH
• roztoky MeSH
• telomery genetika   ultrastruktura   MeSH
• zkracování telomer * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adenin MeSH
• DNA MeSH
• furany MeSH
• oligonukleotidy MeSH
• roztoky MeSH

• Klíčová slova
• ATM mutation, antigenic selection, chronic lymphocytic leukemia, short telomere, stereotyped subset,
• MeSH
• analýza přežití MeSH
• ATM protein genetika   MeSH
• chronická lymfatická leukemie klasifikace   genetika   mortalita   MeSH
• kohortové studie MeSH
• lidé MeSH
• mutace * MeSH
• sekvenční analýza DNA MeSH
• telomery ultrastruktura   MeSH
• zkracování telomer * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• dopisy MeSH
• multicentrická studie MeSH
• práce podpořená grantem MeSH
• Názvy látek
• ATM protein, human MeSH Prohlížeč
• ATM protein 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 vazebné proteiny genetika   metabolismus   ultrastruktura   MeSH
• elektronová mikroskopie MeSH
• fluorescenční polarizace MeSH
• fylogeneze MeSH
• genetická variace MeSH
• lidé MeSH
• molekulární evoluce MeSH
• oligonukleotidy genetika   metabolismus   MeSH
• proteiny vázající telomery klasifikace   genetika   metabolismus   ultrastruktura   MeSH
• retardační test MeSH
• Schizosaccharomyces pombe - proteiny genetika   metabolismus   ultrastruktura   MeSH
• Schizosaccharomyces genetika   MeSH
• sekvence nukleotidů MeSH
• telomery genetika   metabolismus   ultrastruktura   MeSH
• transkripční faktory genetika   metabolismus   ultrastruktura   MeSH
• vazba proteinů MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• DNA vazebné proteiny MeSH
• oligonukleotidy MeSH
• proteiny vázající telomery MeSH
• Schizosaccharomyces pombe - proteiny MeSH
• taz1 protein, S pombe MeSH Prohlížeč
• Teb1 protein, S pombe MeSH Prohlížeč
• transkripční faktory 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 genetika   metabolismus   MeSH
• buněčný rodokmen MeSH
• centromera ultrastruktura   MeSH
• centrozom ultrastruktura   MeSH
• DNA chemie   MeSH
• fenotyp MeSH
• heterochromatin chemie   MeSH
• hybridizace in situ fluorescenční MeSH
• karyotypizace MeSH
• křížení genetické MeSH
• repetitivní sekvence nukleových kyselin MeSH
• telomery ultrastruktura   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA MeSH
• heterochromatin 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
• buněčné linie MeSH
• faktor vyvolávající apoptózu genetika   fyziologie   MeSH
• fenantridiny farmakologie   MeSH
• fluorescenční barviva farmakologie   MeSH
• HeLa buňky MeSH
• lidé MeSH
• mitochondriální membrány metabolismus   MeSH
• mitochondrie metabolismus   MeSH
• nádorové buněčné linie MeSH
• počítačové zpracování obrazu MeSH
• respirační komplex I metabolismus   MeSH
• superoxidy metabolismus   MeSH
• telomerasa metabolismus   MeSH
• telomery ultrastruktura   MeSH
• umlčování genů MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 5-(6'-triphenylphosphoniumhexyl)-5,6-dihydro-6-phenyl-3,8-phenanthridinediammine MeSH Prohlížeč
• faktor vyvolávající apoptózu MeSH
• fenantridiny MeSH
• fluorescenční barviva MeSH
• respirační komplex I MeSH
• superoxidy MeSH
• telomerasa 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 genetika   metabolismus   MeSH
• chromozomy genetika   metabolismus   ultrastruktura   MeSH
• Dinoflagellata genetika   růst a vývoj   metabolismus   ultrastruktura   MeSH
• kapalné krystaly MeSH
• protozoální DNA genetika   MeSH
• repetitivní sekvence nukleových kyselin MeSH
• replikace DNA genetika   MeSH
• telomerasa metabolismus   MeSH
• telomery genetika   metabolismus   ultrastruktura   MeSH
• zlomy DNA MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chromatin MeSH
• protozoální DNA MeSH
• telomerasa MeSH

The terminal chromatin structures at the ends of eukaryotic chromosomes, the telomeres, are a focus of intensive research due to their importance for the maintenance of chromosome integrity. Their shortening due to incomplete replication functions as a molecular clock counting the number of cell divisions, and ultimately results in cell-cycle arrest and cellular senescence. Telomere shortening can be compensated by the nucleoprotein enzyme complex called telomerase, which is able to extend shortened telomeres. In humans, only embryonic and germ cells show telomerase activity that is sufficient for telomere length stability and cellular immortality. Unfortunately, telomerase is activated in cancer cells, which, thus, achieve unlimited growth and a malignant phenotype. Even if there were no any other links of telomere biology to other essential processes in the cell nucleus such as DNA repair, chromosome positioning, and nuclear architecture in mitosis and meiosis, the close connection of telomere biology to aging and cancer makes telomeres and techniques for their analysis important enough from the point of view of us, mortal and disease-prone people. In this chapter, we describe the most common types of analyses used in telomere biology: screening for typical and variant telomeric sequences, determination of telomere lengths, and measurement of telomerase activity.

• MeSH
• buněčný cyklus MeSH
• chromozomy ultrastruktura   MeSH
• endodeoxyribonukleasy metabolismus   MeSH
• fenotyp MeSH
• genetické techniky * MeSH
• hybridizace in situ fluorescenční MeSH
• lidé MeSH
• molekulová hmotnost MeSH
• oprava DNA MeSH
• polymerázová řetězová reakce MeSH
• restrikční enzymy metabolismus   MeSH
• sefarosa chemie   MeSH
• stárnutí buněk MeSH
• telomerasa metabolismus   MeSH
• telomery ultrastruktura   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• endodeoxyribonukleasy MeSH
• exonuclease Bal 31 MeSH Prohlížeč
• restrikční enzymy MeSH
• sefarosa MeSH
• telomerasa MeSH

The ends of linear chromosomes of the vast majority of eukaryotic species possess specialized nucleo-protein structures called telomeres. Regardless of many exceptions, the structure and function of telomeres share high degrees of similarity between various eukaryotes. The underlying DNA structure of telomeres determines the particular setup of telomere chromatin and protein complexes as are telomere-associated proteins and a number of repair and cell cycle checkpoint agents. The structure of telomeres is highly dynamic during the cell's growth, replication, differentiation, senescence, or neoplastic transformation. Although the bulk of our knowledge about telomere function comes from molecular and biochemical studies in model organisms such as yeast and mouse, we want to show--with special emphasis on plants--in this short review that classical methods of plant cytogenetics can significantly complement the above experimental approaches and help in our understanding of telomere functions.

• MeSH
• Arabidopsis genetika   metabolismus   MeSH
• chromozomy rostlin genetika   MeSH
• cytogenetické vyšetření metody   MeSH
• DNA rostlinná genetika   MeSH
• fyziologie rostlin * MeSH
• oprava DNA MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• rostlinné buňky MeSH
• rostliny genetika   MeSH
• telomerasa genetika   metabolismus   MeSH
• telomery genetika   fyziologie   ultrastruktura   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• DNA rostlinná MeSH
• proteiny huseníčku MeSH
• telomerasa MeSH