Estratégias anti-aging baseadas em moléculas químicas naturais como potentes ativadores de telomerase / Anti-aging strategies based on natural chemical molecules as potent telomerase activators / Estrategias antienvejecimiento basadas en moléculas químicas naturales como potentes activadores de la telomerasa

Mesmo em tempos modernos, os grandes avanços tecnológicos não permitem de forma comprovada retardar o envelhecimento nos seres humanos. Neste sentido, uma das estratégias é o uso moléculas químicas naturais que possuem a ação de ativadores de telomerase, uma vez de que a telomerase é uma ribonucleoproteína transcriptase reversa que possui a função de alongar os telômeros e neutralizar a erosão normal dos telômeros. Neste contexto, este estudo de revisão dedicou-se a aprofundar o conhecimento sobre o uso de moléculas químicas naturais derivadas de plantas que possuem função de ativadores de telomerase para atividade anti-aging. Inúmeras moléculas têm sido propostas e, estudas os seus mecanismos com o intuito de desenvolver novas ferramentas para prevenir/retardar e tratar doenças relacionadas a idade e o envelhecimento. Adicionalmente, o uso de moléculas como ativadores da telomerase têm sido um meio de prolongar o encurtamento dos temoleros, como no caso, de moléculas isolada da erva Astragalus membranaceus (TA-65), curcumina, silbinina e alicina; ademais, outras moléculas de origem natural possuem atividade anti-aging comprovadas, conforme reportadas nesta revisão. Sendo assim, a procura por biomarcadores à base de compostos químicos naturais que estimulem a telomerase, a fim de prolongar a vida dos telômero e assim, retardar o processo de envelhecimento do organismo têm despertado o interesse de diversos pesquisadores ao redor do mundo.

Even in modern times, the great technological advances do not allow in a proven way to delay aging in humans. In this sense, one of the strategies is the use of natural chemical molecules that have telomerase activators, since telomerase is a ribonucleoprotein reverse transcriptase that has the function of lengthening telomeres and neutralizing the normal erosion of telomeres. In this context, this review study was dedicated to deepening the knowledge about the use of natural chemical molecules derived from plants that have telomerase activator function for anti-aging activity. Numerous molecules have been proposed and their mechanisms studied in order to develop new tools to prevent/delay and treat aging-related diseases. Additionally, the use of molecules as telomerase activators has been a means of prolonging the shortening of temolers, as in the case of molecules isolated from the herb Astragalus membranaceus (TA-65), curcumin, silbinin and allicin; in addition, other molecules of natural origin have proven anti-aging activity, as reported in this review. Therefore, the search for biomarkers based on natural chemical compounds that stimulate telomerase in order to prolong the life of telomeres and, thus delay the aging process of the organism has aroused the interest of several researchers around the world.

Aún en los tiempos modernos, los grandes avances tecnológicos no permiten de manera comprobada retrasar el envejecimiento en los humanos. En este sentido, una de las estrategias es el uso de moléculas químicas naturales que tengan activadores de la telomerasa, ya que la telomerasa es una ribonucleoproteína transcriptasa inversa que tiene la función de alargar los telómeros y neutralizar la erosión normal de los telómeros. En este contexto, este estudio de revisión se dedicó a profundizar en el conocimiento sobre el uso de moléculas químicas naturales derivadas de plantas que tienen función activadora de la telomerasa para la actividad antienvejecimiento. Se han propuesto numerosas moléculas y se han estudiado sus mecanismos para desarrollar nuevas herramientas para prevenir/retrasar y tratar enfermedades relacionadas con el envejecimiento. Adicionalmente, el uso de moléculas como activadores de la telomerasa ha sido un medio para prolongar el acortamiento de temolers, como es el caso de moléculas aisladas de la hierba Astragalus membranaceus (TA-65), curcumina, silbinina y alicina; además, otras moléculas de origen natural han demostrado actividad antienvejecimiento, como se reporta en esta revisión. Por ello, la búsqueda de biomarcadores basados en compuestos químicos naturales que estimulen la telomerasa para prolongar la vida de los telómeros y así retrasar el proceso de envejecimiento del organismo ha despertado el interés de varios investigadores a nivel mundial.

cGAS guards against chromosome end-to-end fusions during mitosis and facilitates replicative senescence

As a sensor of cytosolic DNA, the role of cyclic GMP-AMP synthase (cGAS) in innate immune response is well established, yet how its functions in different biological conditions remain to be elucidated. Here, we identify cGAS as an essential regulator in inhibiting mitotic DNA double-strand break (DSB) repair and protecting short telomeres from end-to-end fusion independent of the canonical cGAS-STING pathway. cGAS associates with telomeric/subtelomeric DNA during mitosis when TRF1/TRF2/POT1 are deficient on telomeres. Depletion of cGAS leads to mitotic chromosome end-to-end fusions predominantly occurring between short telomeres. Mechanistically, cGAS interacts with CDK1 and positions them to chromosome ends. Thus, CDK1 inhibits mitotic non-homologous end joining (NHEJ) by blocking the recruitment of RNF8. cGAS-deficient human primary cells are defective in entering replicative senescence and display chromosome end-to-end fusions, genome instability and prolonged growth arrest. Altogether, cGAS safeguards genome stability by controlling mitotic DSB repair to inhibit mitotic chromosome end-to-end fusions, thus facilitating replicative senescence.

Cellular consequences of small supernumerary marker chromosome derived from chromosome 12: mosaicism in daughter and father

Constitutional genomic imbalances are known to cause malformations, disabilities, neurodevelopmental delay, and dysmorphia and can lead to dysfunctions in the cell cycle. In extremely rare genetic conditions such as small supernumerary marker chromosomes (sSMC), it is important to understand the cellular consequences of this extra marker, as well the factors that contribute to their maintenance or elimination through successive cell cycles and phenotypic impact. The study of chromosomal mosaicism provides a natural model to characterize the effect of aneuploidy on genome stability and compare cells with the same genetic background and environment exposure, but differing in the presence of sSMC. Here, we report the functional characterization of different cell lines from two familial patients with mosaic sSMC derived from chromosome 12. We performed studies of proliferation dynamics, stability, and variability of these cells using fluorescent in situ hybridization (FISH), sister chromatid exchanges (SCE), and conventional staining. We also quantified the telomere-related genomic instability of sSMC cells using 3D telomeric profile analysis by quantitative-FISH. sSMC cells exhibited differences in the cell cycle dynamics compared to normal cells. First, the sSMC cells exhibited lower proliferation index and higher frequency of SCE than normal cells, associated with a higher level of chromosomal instability. Second, sSMC cells exhibited more telomeric-related genomic instability. Lastly, the differences of sSMC cells distribution among tissues could explain different phenotypic repercussions observed in patients. These results will help in our understanding of the sSMC stability, maintenance during cell cycle, and the cell cycle variables involved in the different phenotypic manifestations.

Effect of RNaseH-1 on inhibition of telomerase-negative osteosarcoma and enhancement of radiosensitivity / 中华放射肿瘤学杂志

Objective:To investigate the effect and mechanism of RNaseH-1 on the radiosensitivity of the osteosarcoma cells via the alternative lengthening of telomeres (ALT) mechanism to maintain the telomere length.Methods:ALT osteosarcoma cell U2OS and telomerase-positive osteosarcoma cell 143B over-expressing RNaseH-1 were constructed by lentiviral transfection. After cell transfection, cell proliferation and cell cycle were determined using CCK-8 assay and flow cytometry. The effect of RNaseH-1 on the radiosensitivity of osteosarcoma cells was examined by colony formation assay. DNA injury (γ-H 2AX foci) was assessed by immunofluorescent assay. The expression levels of related proteins were detected by Western blot. Results:The proliferation abilities of U2OS cells were significantly declined following the over-expression of RNaseH-1, and G 1 cell cycle arrest was noted (all P<0.05). Over-expression of RNaseH-1 in U2OS cells increased the phosphorylated levels of ATM and Chk 2, down-regulated the expression of homologous recombination (HR)-related proteins RAD51 and BRCA1significantly aggravated DNA damage and remarkably enhanced the radiosensitivity (all P<0.05). Over-expression of RNaseH-1 exerted no inhibitory effect upon the telomerase-positive 143B cells ( P>0.05). Conclusion:RNaseH-1 over-expression suppresses telomerase-negative osteosarcoma cells and enhances the radiosensitivity probably via the role of RNaseH-1 in inhibiting the homologous recombination repair and activating the ATM signaling pathway.

Inhibition of p53 and/or AKT as a new therapeutic approach specifically targeting ALT cancers

While the majority of all human cancers counteract telomere shortening by expressing telomerase, ~15% of all cancers maintain telomere length by a telomerase-independent mechanism known as alternative lengthening of telomeres (ALT). Here, we show that high load of intrinsic DNA damage is present in ALT cancer cells, leading to apoptosis stress by activating p53-independent, but JNK/c-Myc-dependent apoptotic pathway. Notably, ALT cells expressing wild-type p53 show much lower apoptosis than p53-deficient ALT cells. Mechanistically, we find that intrinsic DNA damage in ALT cells induces low level of p53 that is insufficient to initiate the transcription of apoptosis-related genes, but is sufficient to stimulate the expression of key components of mTORC2 (mTOR and Rictor), which in turn leads to phosphorylation of AKT. Activated AKT (p-AKT) thereby stimulates downstream anti-apoptotic events. Therefore, p53 and AKT are the key factors that suppress spontaneous apoptosis in ALT cells. Indeed, inhibition of p53 or AKT selectively induces rapid death of ALT cells in vitro, and p53 inhibitor severely suppresses the growth of ALT-cell xenograft tumors in mice. These findings reveal a previously unrecognized function of p53 in anti-apoptosis and identify that the inhibition of p53 or AKT has a potential as therapeutics for specifically targeting ALT cancers.

Exercício físico e comprimento dos telômeros: uma revisão sistemática nas disfunções crônico-degenerativas / Physical exercise and telomere length: a systematic review in chronic-degenerative dysfunctions

Introdução: Os telômeros estão localizados nas extremidades dos cromossomos e constituem-se de sequências do DNA e proteínas associadas. O exercício físico parece ter relação com um maior comprimento de telômeros, porém, pouco se sabe sobre o impacto deste na dinâmica telomérica de pessoas com disfunções crônico-degenerativas. Objetivo: Revisar sistematicamente a literatura a respeito do efeito do exercício no comprimento dos telômeros em pessoas com disfunções crônico-degenerativas. Métodos: Foram realizadas buscas por dois investigadores independentes nas bases de dados Pubmed, Scopus, Lilacs e Cochrane Controlled Trials Database, analisando publicações nos idiomas inglês e português. Resultados: Foram encontrados 845 estudos, onde destes, quatro atenderam aos critérios de elegibilidade e seguiram para síntese. Conclusão: Embora o encurtamento dos telômeros esteja relacionado ao estilo de vida, herança genética e doenças do envelhecimento, ainda não está claro se o exercício físico pode atenuar tal processo de encurtamento de forma significativa em indivíduos com disfunções crônico-degenerativas, como excesso de peso e diabetes.

Introduction: Telomeres are located at the ends of chromosomes and consist of DNA sequences and associated proteins. Physical exercise seems to be related to a greater telomeres length, but little is known about its impact on the telomere dynamics of people with chronic degenerative dysfunctions. Purpose: Systematically review the literature on the effect of exercise on the telomeres length in people with chronic degenerative disorders. Methods: Searches were carried out by two independent researchers in the databases Pubmed, Scopus, Lilacs e Cochrane Controlled Trials Database, analyzing publications in the English and Portuguese language. Results: A total of 845 studies were found, of which four met the eligibility criteria and followed up for synthesis. Conclusion: Although shortening of telomeres is related to lifestyle, genetic inheritance, and diseases of aging, still unclear physical exercise can attenuate such a shortening process significantly in individuals with chronic-degenerative dysfunctions such as overweight and diabetes.

Development and characterization of polyclonal antibodies against the linker region of the telomere-binding protein TRF2

Background: TRF2 (telomeric repeat binding factor 2) is an essential component of the telomere-binding protein complex shelterin. TRF2 induces the formation of a special structure of telomeric DNA and counteracts activation of DNA damage-response pathways telomeres. TRF2 has a poorly characterized linker region (udTRF2) between its homodimerization and DNA-binding domains. Some lines of evidence have shown that this region could be involved in TRF2 interaction with nuclear lamina. Results: In this study, the fragment of the TERF2 gene encoding udTRF2 domain of telomere-binding protein TRF2 was produced by PCR and cloned into the pET32a vector. The resulting plasmid pET32a-udTRF2 was used for the expression of the recombinant udTRF2 in E. coli RosettaBlue (DE3). The protein was isolated and purified using ammonium sulfate precipitation followed by ion-exchange chromatography. The purified recombinant protein udTRF2 was injected into guinea pigs to generate polyclonal antibodies. The ability of anti-udTRF2 antibodies to bind endogenous TRF2 in human skin fibroblasts was tested by western blotting and immunofluorescent staining. Conclusions: In this study, the recombinant protein udTRF2 and antibodies to it were generated. Both protein and antibodies will provide a useful tool for investigation of the functions of the udTRF2 domain and its role in the interaction between TRF2 and nuclear lamina.

Application of atomic force microscopy-based single molecule force spectroscopy in G-quadruplex studies / 南方医科大学学报

Telomere plays a crucial role in the physiological and pathological processes of cells. At the end of the telomere, the single-stranded DNA repeat sequence rich in guanine (G) folds in the presence of monovalent metal ions such as Na or K to form a G-quadruplex structure. This structure can not be extended by telomerase and inhibits the activity of telomerase, thus becoming a potential anticancer target. Stabilizing the formation of DNA G-quadruplex structures by small molecule ligands has become a new strategy for designing many anticancer drugs, and studying the interaction strength of these small molecule ligands with G-quadruplex is thus of particular importance for screening highly effective anticancer drugs. Single molecule force spectroscopy enables direct measurement of the interaction between small molecule ligands and G-quadruplexes. This review highlights the advances of single-molecule force spectroscopy based on atomic force microscopy in the study of the G quadruplex structure and its interaction with small molecule ligands, and summarizes the application and development trend of single molecule force spectrum technology in G quadruplex.

TGF-beta receptor mediated telomerase inhibition, telomere shortening and breast cancer cell senescence

Human telomerase reverse transcriptase (hTERT) plays a central role in telomere lengthening for continuous cell proliferation, but it remains unclear how extracellular cues regulate telomerase lengthening of telomeres. Here we report that the cytokine bone morphogenetic protein-7 (BMP7) induces the hTERT gene repression in a BMPRII receptor- and Smad3-dependent manner in human breast cancer cells. Chonic exposure of human breast cancer cells to BMP7 results in short telomeres, cell senescence and apoptosis. Mutation of the BMPRII receptor, but not TGFbRII, ACTRIIA or ACTRIIB receptor, inhibits BMP7-induced repression of the hTERT gene promoter activity, leading to increased telomerase activity, lengthened telomeres and continued cell proliferation. Expression of hTERT prevents BMP7-induced breast cancer cell senescence and apoptosis. Thus, our data suggest that BMP7 induces breast cancer cell aging by a mechanism involving BMPRII receptor- and Smad3-mediated repression of the hTERT gene.

Shortened telomere length in bipolar disorder: a comparison of the early and late stages of disease

Objective: Bipolar disorder (BD) has been associated with increased rates of age-related diseases, such as type II diabetes, metabolic syndrome, osteoporosis, and cardiovascular disorders. Several biological findings have been associated with age-related disorders, including increased oxidative stress, inflammation, and telomere shortening. The objective of this study was to compare telomere length among participants with BD at early and late stages and age- and gender-matched healthy controls. Methods: Twenty-six euthymic subjects with BD and 34 healthy controls were recruited. Genomic DNA was extracted from peripheral blood and mean telomere length was measured using real-time quantitative polymerase chain reaction. Results: Telomere length was significantly shorter in both the early and late subgroups of BD subjects when compared to the respective controls (p = 0.002 and p = 0.005, respectively). The sample size prevented additional subgroup analyses, including potential effects of medication, smoking status, and lifestyle. Conclusion: This study is concordant with previous evidence of telomere shortening in BD, in both early and late stages of the disorder, and supports the notion of accelerated aging in BD.

Expression of human protection of telomere 1 and its relationship with Helicobacter pylori infection in gastric carcinoma / 肿瘤研究与临床

Objective To determine the expression of human protection of telomeres 1 (hPOT1) and its relationship with Helicobacter pylori (HP) infection in gastric carcinoma.Methods The expressions of hPOT1 protein and hPOT mRNA were detected in 53 gastric carcinoma specimens (observed group) and 20 normal gastric mucosa tissues (control group) by SP immunohistochemical method and in situ hybridization (ISH), respectively.HP infection was examined by Warthin-Starry method in observed group.Results The positive expression rate of hPOT1 protein was 84.91％ (45/53) in observed group, higher than that in control group [30.00 ％ (6/20)] (P ＜ 0.01).The positive expression rate of hPOT1 mRNA was 58.49 ％ (31/53) in observed group, higher than that in control group [10.00 ％ (2/20)] (P ＜ 0.05).The positive co-expression rate of hPOT1 protein and mRNA was 56.60 ％ (30/53), both had positive relationship in gastric carcinoma (r =0.394, P ＜ 0.05).The rate of HP infection in 53 cases of gastric carcinoma was 52.83 ％ (28/53).The positive expression rates of hPOTI protein and mRNA in observed group with HP infection were significantly higher than those in observed group without HP infection[protein: 96.43 ％ (27/28) vs 72.00 ％ (18/25), P ＜0.05;mRNA: 85.75 ％ (24/28) vs 28.00 ％ (7/25), P ＜ 0.01].Conclusions hPOT1 may be associated with occurrence of gastric carcinoma.Combined detection of hPOT1 protein and mRNA can be used for the diagnosis of gastric carcinoma.HP infection may be associated with abnormal expression of hPOT1 in occurrence of gastric carcinoma.

Study of human telomere G4-DNA stabilizers / 中国药理学通报

Telomere maintenance plays a critical role in cancer progression.Approximately 85% human cancer cells maintain their telomere length through activation of telomerase.Other 15%of cancers maintain telomere length independently of telom-erase by alternative lengthening of telomeres (ALT)pathway. Both events are equally important for telomere length mainte-nance of cancer cells.Human telomere consists of a series of G rich DNA sequences,which could form G-quadruplex.The for-mation of this structure can block the extension of telomeres by telomerase or ALT,resulting in cancer cell death.Thereby,G-quadruplex has been one of the focuses of anticancer therapy in recent years.This review focuses on the latest progress of G-quadruplex stabilizers.

Stem cell function and maintenance – ends that matter: Role of telomeres and telomerase.

Stem cell research holds a promise to treat and prevent age-related degenerative changes in humans. Literature is replete with studies showing that stem cell function declines with aging, especially in highly proliferative tissues/ organs. Among others, telomerase and telomere damage is one of the intrinsic physical instigators that drive agerelated degenerative changes. In this review we provide brief overview of telomerase-deficient aging affects in diverse stem cells populations. Furthermore, potential disease phenotypes associated with telomerase dysregulation in a specific stem cell population is also discussed in this review. Additionally, the role of telomerase in stem cell driven cancer is also briefly touched upon.

Relationship between single-nucleotide polymorphisms of human protection of telomeres 1 genes and gastric cancer / 中华消化外科杂志

Objective To investigate the relationship between single-nucleotide polymorphisms of IVS13-98G/T of human protection of telomeres 1 (hPOT1) genes and gastric cancer. Methods A total of 168 patients with gastric cancer (gastric cancer group) who had been admitted to Wuwei Cancer Hospital, Wuwei People's Hospital and Liangzhou District Hospital from December 2005 to July 2006 and 156 healthy people (control group) were genotyped by polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism (PCR-RFLP) method, and the relationship between the distribution of genotypes and the risk faetors of gastric cancer was analyzed. The distribution of genotypes and allele frequency between the 2 groups were compared by chi-square test. Hardy-weinberg equilibrium test was adopted to determine whether the distribution of genotypes and allele frequency were representative. Relative risk and 95% confidence interval were calculated by non-conditional Logistic regression model. Results The frequencies of genotypes GG, GT and TT of hPOT1IVS13-98 G/T were 21.4%, 41.7% and 36.9% in gastric cancer group, and 24.4%, 51.9% and 23.7% in control group. The allele frequencies of G- and T-allele were 42.3%, 57.7% in gastric cancer group, and 49.7%, 50.3% in control group. There was no significant difference in allele frequencies of G- and T-allele between the 2 groups (X~2=3.58, P>0.05). Compared with genotype TT, the relative risks for GT and GG were 0.439 (95% CI: 0.251-0.767, P < 0.05) and 0.514 (95 % CI: 0.264-0.999, P=0.05). There was no influence of different genotypes of hPOT1IVS13-98 G/T, sex, smoking history, family history of cancer on gastric cancer. Conclusion Single-nucleotide polymorphisms of IVS13-98G/T of hPOT1 may be a protective factor of gastric cancer.

A telomerase em células-tronco hematopoéticas: [revisão] / Telomerase in hematopoietic stem cells: [review]

A proliferação das células-tronco hematopoéticas sofre a perda dos telômeros a cada divisão celular. Alguns autores discordam quanto à perda ou não do potencial proliferativo e capacidade de auto-renovação das células mais diferenciadas. Revisaremos aqui o papel da telomerase na biologia do sistema hematopoético, na diferenciação normal ou maligna, assim como no envelhecimento das células-tronco hematopoéticas. A constante renovação celular requerida pela hematopoese confere às células-tronco embrionárias, assim como à maioria das células tumorais, um aumento da capacidade proliferativa marcada pela detecção da enzima telomerase e possível manutenção dos telômeros. Estudos clínicos se farão necessários para esclarecer melhor a atividade da telomerase em células-tronco hematopoéticas, seu possível uso como marcador de diagnóstico e seu uso a fim de propósitos prognósticos.

Hematopoietic stem cell proliferation leads to telomere length decreases at each cellular division. Some authors disagree about the telomere influence on the reduction of the proliferative potential and capacity of self renewal. Here we review telomerase function in the biology of the hematopoietic system, in normal or differentiation and its influence on the ageing of hematopoietic stem cells. The constant cellular renewal required to maintain the hematopoietic system, provides embryonic stem cells, as well as malignant cells, an increased proliferative capacity. This is marked by the detection of telomerase enzyme activity and possible telomere maintenance. Clinical trials will be required to clarify telomerase activity in hematopoietic stem cells, its possible use as a diagnostic marker and its use for prognostic purposes.

Kidneys with bad ends

Telomeres consist of tandem guanine-thymine(G-T) repeats in most eukaryotic chromosomes. Human telomeres are predominantly linear, double stranded DNA as they ended in 30-200 nucleotides(bases,b) 3'-overhangs. In DNA replication, removal of the terminal RNA primer from the lagging strand results in a 3'-overhang of uncopied DNA. This is because of bidirectional DNA replication and specificity of unidirectional DNA polymerase. After the replication, parental and daughter DNA strands have unequal lengths due to a combination of the end- replication problem and end-processing events. The gradual chromosome shortening is observed in most somatic cells and eventually leads to cellular senescence. Telomere shortening could be a molecular clock that signals the replicative senescence. The shortening of telomeric ends of human chromosomes, leading to sudden growth arrest, triggers DNA instability as biological switches. In addition, telomere dysfunction may cause chronic allograft nephropathy or kidney cancers. The renal cell carcinoma(RCC) in women may be less aggressive and have less genomic instability than in man. Younger patients with telomere dysfunction are at a higher risk for RCC than older patients. Thus, telomeres maintain the integrity of the genome and are involved in cellular aging and cancer. By studying the telomeric DNA, we may characterize the genetic determinants in diseases and discover the tools in molecular medicine.

El nucléolo como un regulador del envejecimiento celular / The nucleolus as a regulator of cellular senescence

El nucléolo, considerado únicamente como el sitio de síntesis de los ribosomas, actualmente representa una estructura nuclear dinámica que participa en la regulación de importantes procesos celulares. Numerosas evidencias han demostrado que el envejecimiento celular es una de las diversas funciones que son controladas por el nucléolo. Las mutaciones en las proteínas de localización nucleolar promueven el envejecimiento prematuro en levaduras y humanos. La carencia de represión en la transcripción de genes que codifican para el ARNr que se encuentran dañados, y las mutaciones en las helicasas del ADN encargadas de minimizar la formación de círculos extra-cromosómicos del ADN que codifica para el ARNr, provocan modificaciones en la estructura del nucléolo e inducen envejecimiento prematuro en levaduras. De igual manera, en los humanos la carencia de las helicasas del ADN localizadas en el nucléolo y que participan en el mantenimiento de la integridad genómica, favorecen el desarrollo de aquellas enfermedades asociadas con el envejecimiento acelerado. Además, la presencia de algunos componentes de la telomerasa en el nucléolo, indica que parte de la biosíntesis de esta enzima se realiza en esta estructura nuclear, sugiriendo una conexión entre el nucléolo y la síntesis de los telómeros en la regulación del envejecimiento celular. Por otra parte, el nucléolo secuestra proteínas para regular su actividad biológica durante el inicio o término de la vida replicativa celular.

The nucleolus has been considered originally only as the site for the ribosome synthesis, but now it is well known that it represents a dynamic nuclear structure involved in important cellular processes. Several evidences have demonstrated that the nucleolus regulates the cellular senescence. Specific mutations on the DNAs codifying for nucleolar proteins induced premature senescence from yeast to human. The failure to repress the genes transcription codifying for damaged rRNA, and the mutations in DNA helicases, which minimizes the formation of DNA extra-chromosomal circles codifying for rRNA, modify the nucleolar structure and induce premature senescence in yeast. Similarly, in humans, the reduction of these DNA helicases levels, which are localized in the nucleoli and participate in maintenance of genomic integrity, helps to the development of those diseases associated with premature senescence. Furthermore, the presence in the nucleolus of some telomerase components, indicates that part of the biosynthesis of this enzyme occurred in this nuclear structure; suggesting a communication between the nucleolus and the synthesis of the telomeres in the regulation of cell senescence. On the other hand, the nucleolus sequesters proteins to regulate its own biological activity, from the start to the end of cellular replication. In addition this nuclear structure is involved in the biosynthesis of most cellular ribonucleoprotein particles, as well as in cell cycle regulation, making it central to gene expression. In conclusion, the nucleolus became a multifunctional subnuclear structure involved from cell proliferation to cell senescence.

Expression of human protection of telomeres1 (POT1) and telomeric repeat binding factor-2 (TRF2)in laryngneal squamous cell carcinoma / 中国耳鼻咽喉头颈外科

OBJECTIVE To study the significance by analyzing the expression of human protection of telomeres1(POT1)and telomeric repeatbinding factor-2(TRF2)in the tissues of laryngneal squamous cell carcinoma(LSCC)and in polyp of vocal cord tissues. METHODS The expression of POT1 and TRF2 in 20 tumor samples and 19 polyp of vocal cord were determined by the indirect immunofluorescence method. The results were scored and analyzed statistically. RESULTS The positive expression rates of POT1 and TRF2 in tumor samples was 65.00% and 70.00% respectively. There were no positive expression of POT1 and TRF2 in polyp of vocal cord. The positive expression of POT1 was higher in poorly differentiated laryngeal carcinoma than that in well-differentiated and moderately differentiated laryngeal carcinoma(Chi-square test with contingency table, P0.05). CONCLUSION The expression of POT1 and TRF2 in laryngneal squamous cell carcinoma were remarkable, POT1 and TRF2 may play a critical role in tumorigenesis of laryngneal squamous cell carcinoma. There was statistical significant difference for degrees of POT1 expression in different tumor histological grades.

Suppression of the expression of hPOT1 gene in human gastric cancer cell line SGC-7901 with vector-based RNA interference technique / 解放军医学杂志

Objective To construct the expression vector of siRNA targeting the human protection of telomeres (hPOT1) gene for the observation of the inhibitory effect of the vector on hPOT1 gene expression in gastric cancer cell line SGC-7901, and to offer a ground work for further study on the roles of hPOT1 in growth and proliferation of gastric cancer cells. Methods 64 base-pair oligonucleotide for small interfering RNA expression targeting hPOT1 gene was designed and chemically synthesized. After annealing, double oligonucleotides were inserted into the downstream of H1 RNA promoter of pSUPER to recombine psiRNA-hPOT1 plasmids, and transiently transfected into gastric cancer cell line SGC-7901 with liposome-mediated transfection after restriction enzyme and sequencing analysis. Semi-quantitative RT-PCR was used to detect the expression levels of hPOT1 gene. Result Recombinant psiRNA-hPOT1 vector was confirmed by sequencing analysis. The results demonstrated that 64nt had been inserted into the expected site. Furthermore, the inserted sequence was exactly correct. The recombinant psiRNA-hPOT1 vector could significantly suppress the hPOT1 expression in gastric cancer cell line SGC-7901. Conclusion The constructed siRNA expression vector of hPOT1 gene psiRNA-hPOT1 recombinant plasmid can block the expression of hPOT1 gene in gastric cancer cell line SGC-7901.

Relationship of POT1 mRNA expression and telomerase activity with incidence of gastric carcinoma / 第三军医大学学报

Objective To study of relationship of the mRNA expression of protection of telomeres 1(POT1) and the activity of telomerase with the incidence of gastric carcinoma.Methods Lesioned gastric mucosal tissues and the corresponding normal tissues from 30 cases of gastric cancer,30 cases of moderate or severe atypical hyperplasia,and 30 cases of intestinal metaplasia were collected in this study.The expression of POT1 mRNA was detected with real time-PCR and the activity of telomerase was examed with TRAP-ELISA.Results Real time-PCR analysis showed that POT1 expression was increased in the gastric carcinoma tissues compared with the paracancerous normal mucosal tissues,increased in the severe atypical hyperplasia than in the corresponding normal tissues,but there was no difference between intestinal metaplasia tissues and normal tissues.The activity of telomerase in the advanced gastric tumors and severe atypical hyperplasia was significantly higher than that in intestinal metaplasia tissues and normal gastric mucosal tissues.However no obvious difference was found in the activity in gastric tumors and severe atypical hyperplasia with intestinal metaplasia tissues and normal gastric mucosal tissues.Conclusion Although the activity of telomerase in gastric cancer and severe atypical hyperplasia is significantly higher than that in normal and intestinal metaplasia tissues,POT1 mRNA has no relationship with this change.