Enzyme Telomerase Research Articles

Vitamin D controls cancer by regulating telomere and telomerase

Deficiency of vitamin D in the body may cause many disorders and diseases including cancer. Vitamin D receptors are one of the most important nuclear receptors responsible for transcription and cellular proliferation and thus affects telomere and telomerase. Telomerase enzymes is responsible for transcription and copies the telomere. The process of telomere copying leads to absence of cell death and thus causes the cellular proliferation of cells within the body. If maintained at normal level, vitamin D regulates and controls the processes of cellular replication and proliferation leading to control and regulation of rate of secretion of telomerase which in turn maintains the appropriate telomere length. Since telomerase is one of the primary factors of cancer spread, telomerase regulation and control can lead to cancer control. Therefore, by maintaining normal vitamin D level in the body DNA can be protected from damage.

Pro-apoptotic, anti-metastatic, and anti-telomerase activity of Tinospora cordifolia and its active polysaccharide arabinogalactan during Benzo(a)pyrene-induced lung carcinogenesis.

BACKGROUND:The present study aims to unravel the pro-apoptotic, anti-metastatic, and anti-telomerase activity of aqueous extract of Tinospora cordifolia stem (Aq.Tc) and its active component arabinogalactan (AG) during Benzo(a)pyrene [B(a)P]-induced lung tumorigenesis in mice.MATERIALS AND METHODS:Lung tumors were induced in male BALB/c mice using B(a)P as a carcinogen. Animals were administered twice with 50 mg/kg b.wt (i.p.) dosage of B(a)P at the 2nd and 4th week of the study. Mice were orally treated with Aq.Tc and AG on alternate days at a dose of 200 mg/kg b.wt and 7.5 mg/kg b.wt, respectively, for continuous 22 weeks.RESULTS:Oral administration of animals with Aq.Tc and AG suppressed the development of lung carcinogenesis by modulating the mRNA and protein expressions of different apoptotic genes; bcl-2, bax, caspase 3, and caspase 9. The pro-apoptotic proficiency of Aq.Tc and AG was further confirmed by DNA agarose gel electrophoresis showing fragmentation in B(a)P + Aq.Tc group and smear formation in B(a)P + AG group. In contrast to the control group, an increase in tumor invasion factors such as matrix metalloproteinases-2 (MMP-2) and MMP-9 was also observed in B(a)P treated animals. Nevertheless, Aq.Tc and AG treatment effectively mitigated the B(a)P-induced upregulation of MMP-2 and MMP-9. The activity of the telomerase enzyme was also observed to be upregulated in B(a)P treated animals which consecutively found to get normalized with the parallel administration of Aq.Tc and AG.CONCLUSION:Aq.Tc and AG successfully mitigated the altered expression of apoptosis, metastasis, and telomerase activity-associated genes during pulmonary carcinogenesis.

Repositioning anticancer drugs as novel COVID-19 antivirals: targeting structural and functional similarities between viral proteins and cancer.

Abstract The current COVID-19 pandemic contributed by the SARS-CoV-2 has put in place an urgent need for new and promising antiviral therapeutics. The viral RNA-dependent RNA polymerase (RdRp) enzyme plays a vital role in viral replication for all RNA viruses, including SARS-CoV-2, thereby making it a prime and promising candidate for novel antiviral targeting. Interestingly, the human telomerase reverse transcriptase (hTERT), a common catalytic subunit of the telomerase enzyme in many cancers, has also been identified with structural and functional similarities to the viral RdRp. Therefore, it becomes essential to evaluate and consider anticancer drugs that target hTERT towards antiviral RdRp activity, and vice versa. For instance, Floxuridine, an hTERT inhibitor, and VX-222, a hepatitis C virus RdRp inhibitor, are now gaining recognition as a potential antiviral against SARS-CoV-2 and anti-hTERT for cancer, simultaneously. While limited studies on hTERT inhibitors for use as viral RdRp, and anti-RdRp inhibitors as hTERT inhibitors are available, in this review, we aim at bringing to light this close structural and functional relationship between both these enzymes. We punctuate this idea with specific examples on how potential anticancer inhibitors can effectively be brought to use as inhibitors against the SARS-CoV-2 virus, a relatively new pathogen, compared to the very well-studied field of cancer research.

Monitoring Telomere Maintenance During Regeneration of Annelids.

Telomere shortening is a hallmark of aging and eventually constrains the proliferative capacity of cells. The protocols discussed here are used for monitoring telomeres comprehensively in Aeolosoma viride, a model system for regeneration studies. We present methods for analyzing the activity of telomerase enzyme in regenerating tissue by telomeric repeat amplification protocol (TRAP) assay, for comparing telomere length between existing tissue and newly regenerated tissue by telomere restriction fragment (TRF) assay, as well as for visualizing telomeres by fluorescence in situ hybridization (FISH).

Активное долголетие женщины: теломеразная теория старения в основе ведения менопаузального периода

The concept of women’s long-term health and longevity implies maintaining the quality of life, including a discussion of the role of hormone replacement therapy within the ‘therapeutic window’. Aging is a complex multi-step process. It is believed that women begin to experience the effects of aging at the age of 40. The processes of age-related changes in the body are being actively studied these days and include markers, models, systems, but there is no unified concept yet. In recent decades, there has been an increase in life expectancy for women, hence there are more women in menopause, and an increase in the incidence of age-related diseases can be expected. With the onset of menopause and age-related changes, women may experience metabolic disorders, cardiovascular diseases, endothelial dysfunction, disorders of both the central and peripheral nervous systems, musculoskeletal disrders and mental health problems. Over past decades, attention has been paid to cellular markers of aging, and the telomere theory has been most developed. It is associated with shortening of telomeres – the end regions of chromosomes. Many studies in recent years have examined the mechanisms influencing the length of these regions, the activity of the telomerase enzyme, and the processes of reproductive aging associated with this theory. In the 20th and 21st centuries, the possible effect of exogenously administered estrogen on telomere length as part of hormone replacement therapy has been under active consideration. Key words: insulin resistance, menopause, telomeres, telomerase, type 2 diabetes, aging, hormone replacement therapy

Telomerase and neurons: an unusual relationship.

Most people associate the enzyme telomerase with its role in maintaining telomeres, which is its best-known canonical role. For this important function, two main components are required: the protein telomerase reverse transcriptase (TERT) and the telomerase RNA component. In addition, over the last decades, an ever-growing number of other, non-telomeric, non-canonical functions for the telomerase protein TERT has been established. These reach from tumor promotion to decreasing oxidative stress and apoptosis as well as activating autophagy. These functions are more and more recognized as being important in many tissues and physiological as well as pathological conditions. The role of telomerase in brain development and neuronal cells has been investigated for more than 20 years. However, the non-telomeric role in non-dividing neurons of the brain for telomerase and the TERT-protein has only recently been highlighted by extensive research. Moreover, these developments promoted the suggestion of a beneficial and protective role of TERT against neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease. This review summarizes the most important findings in the field of telomerase in neurons and gives an outlook onto possible therapeutic applications of boosting telomerase/TERT levels with telomerase activators to prevent or ameliorate various neurodegenerative diseases.

Measurement of paraoxonase and telomerase enzymes and HDL (high density lipoprotein) values and research of their possible relationships with each other in bloodserum of obese cats

Today, obesity is seen as a serious health problem in domestic cats. Paraoxonase1 (PON1) is a negative acute phase protein with anti-inflammatory properties. PON1 is transported by linking to different parts of HDL in the blood and has a protective feature of HDL against oxidation. Telomerase is reverse transcriptase enzyme that synthesizes and protects telomeres. Telomere length becomes shorter due to stress, obesity, and lack of exercise. In this study, paraoxonase1, telomerase enzymes and HDL values in blood serum of obese and non-obese cats were measured and their relationships with each other were evaluated. Body fat ratio in cats with body fat measurement system, those above 30% were evaluated as obese, and those below 30% were evaluated as the control group. Paraoxonase1 (p<0.001), telomerase (p<0.001) and HDL (p<0.008) values showed a statistically significant difference between the both groups, it was found to be lower in the obese group compared to the control group. As a result; paraoxonase1 and telomerase enzymes which are parameters of oxidative stress and are known to decrease in inflammation, were also found to be decreased in obese cats. The fact that HDL values are lower than the control group is an indicator that there are diseases that occur together with obesity.

Transgenic Immortalization of Human Dermal Fibroblasts Mediated Through the MicroRNA/SIRT1 Pathway.

Human dermal fibroblasts (HDFs) are widely used as a skin model in cosmetic and pharmaceutical industry due their advantages for the cosmetic industry and medical aspects. Telomeres are key players in controlling cellular aging, in which telomeres and the telomerase enzyme (hTERT) can maintain proliferative capacity and prolong cellular senescence. The primary aim of the study was to elucidate the underlying mechanisms of hTERT/SV40 immortalization of human dermal fibroblasts. Transgenic expression of hTERT and SV40 large antigen, as well as co-transfection of both factors was performed and their significance evaluated in terms of HDF immortalization efficiency. The results showed that the immortalized fibroblasts of all conditions can be cultured in over 60 passages and maintain their telomere length. Further, key markers of skin cells, such as COL1A1, KRT18 and ELASTIN, were up-regulated in immortalized cells. In addition, p53 expression was enhanced in all immortalized cells, in accordance with activation of the SIRT1 gene upon transgenic immortalization. The significant role of SIRT1 in fibroblast proliferation was assessed by shRNA-knockdown, and it was found that SIRT1 silencing led to loss of Ki67, a proliferation marker. Moreover, miR-93, a SIRT1-targeted miRNA, also had a significantly reduced expression in the co-transfected immortalized cells, highlighting the linkage of the miRNA and SIRT1 pathway in the immortalization of human dermal fibroblasts. This evidence from this study could benefit the efficient development of human skin cell lines for use in the cosmetic industry in the future.

Effects of in vitro short- and long-term treatment with telomerase inhibitor in U-251 glioma cells.

The inhibition of the enzyme telomerase (TERT) has been widely investigated as a new pharmacological approach for cancer treatment, but its real potential and the biochemical consequences are not totally understood. Here, we investigated the effects of the telomerase inhibitor MST-312 on a human glioma cell line after both short- and long-term (290 days) treatments. Effects on cell growth, viability, cell cycle, morphology, cell death and genes expression were assessed. We found that short-term treatment promoted cell cycle arrest followed by apoptosis. Importantly, cells with telomerase knock-down revealed that the toxic effects of MST-312 are partially TERT dependent. In contrast, although the long-term treatment decreased cell proliferation at first, it also caused adaptations potentially related to treatment resistance and tumor aggressiveness after long time of exposition. Despite the short-term effects of telomerase inhibition not being due to telomere erosion, they are at least partially related to the enzyme inhibition, which may represent an important strategy to pave the way for tumor growth control, especially through modulation of the non-canonical functions of telomerase. On the other hand, long-term exposure to the inhibitor had the potential to induce cell adaptations with possible negative clinical implications.

Prognostic significance of serum telomerase activity in the monitoring of hepatitis B viral infection

ABSTRACT Hepatitis B viral infection could be complicated by hepatocellular degeneration, liver cirrhosis, and cancer. A total of 87 participants – 29 each of symptomatic and asymptomatic hepatitis B positive, and hepatitis B negative individuals (controls) – were recruited, and their serum samples were evaluated for serum telomerase (a biomarker for cell aging and tumorigenesis), alpha fetoprotein, and liver enzymes. Serum telomerase of the symptomatic group was higher than that of the asymptomatic group and the control (P < .001). Serum α-fetoprotein in the symptomatic group was also higher than the asymptomatic group and the controls (P < .001). The mean AST value for the symptomatic test group was higher than the asymptomatic test group and the control (P < .001). The mean ALT value for the symptomatic test group was higher than the asymptomatic test group and the control (P < .001). However, serum α-fetoprotein, AST, and ALT in the asymptomatic group were not significantly different from the controls. Serum telomerase activity was higher in symptomatic and asymptomatic HBV subjects compared with controls; this provides better information than AFP and liver enzymes that were only higher in symptomatic subjects. Serum telomerase activity could therefore be used as a marker in predicting the onset of hepatocarcinogenesis. Abbreviation list HBV: Hepatitis B virus; AFP: Alpha fetoprotein; ALT: Alanine transaminase; AST: Aspartate transaminase; HCC: Hepatocellular carcinoma; ELISA: Enzyme-linked immunosorbent assay; CLD: Chronic liver disease; CMV: Cytomegalovirus; TERT: Telomerase reverse transcriptase; TERC: Telomerase RNA component; WHO: World Health Organization; BUHREC: Babcock University Health Research Ethics Committee; CTL: Cytotoxic T-lymphocyte

"Neural stem cells puzzle" missing piece: telomerase reverse transcriptase expression patterns during nervous system ontogenesis in rats.

For almost three decades, neural stem cells remain still up-to-date and enigmatic topic. The main problem for their studying is the non-existence of an exclusive neural stem cell marker and the heterogeneity of them across the nervous system. As one of the novel markers of neural stem/progenitor cells may serve telomerase reverse transcriptase (TERT), a catalytic subunit of the telomerase enzyme, responsible for retaining the cell immortality. Thus, the aim of our study was to reveal if TERT, as an enzyme for ensuring the immortality of proliferating cells, could be used as a potential marker of neural stem/progenitor cells during the ontogenesis of the rat central nervous system. In this study, we used various markers related to neural stem or progenitor cells character and examined their co-localization with TERT expression. Our experiments were performed on the tissue of the brain and spinal cord during several stages of postnatal development and the neural tube during the 14th embryonal day. Cytoplasmatic TERT expression was found in alar plate progenitors and ventral horn neuroblasts of E14 rats. In the postnatal stages of spinal cord ontogenesis, a cytoplasmatic expression in neurons and nuclear expression in astrocytes was defined. In the brain, nuclear TERT expression was found in neural progenitor cells of neurogenic areas. This study provides the first comparative study of TERT expression across the central nervous system ontogenesis. The nuclear presence of TERT may be used as a potential marker of neural stem/progenitor cells, however, further studies are required to confirm these assumptions.

SMAR1 suppresses the cancer stem cell population via hTERT repression in colorectal cancer cells.

One of the hallmarks of a cancer cell is the ability for indefinite proliferation leading to the immortalization of the cell. Activation of several signaling pathways leads to the immortalization of cancer cells via the reactivation of enzyme telomerase (hTERT). hTERT is active in germ cells, stem cells and also cancer cells. An earlier report from our lab suggests that SMAR1, a tumor suppressor protein, is significantly downregulated in the higher grades of colorectal cancers. Our study identifies SMAR1 as a transcriptional repressor of hTERT. We find that SMAR1 interacts with HDAC1/mSin3a co-repressor complex at the hTERT promoter and brings about HDAC1-mediated transcriptional repression of the promoter. Most solid tumors including colorectal cancer reactivate hTERT expression as it confers several advantages to the cancer cells like increased proliferation and angiogenesis. One of these non-canonical functions of hTERT is inducing the pool of cancer stem cell population. We find that in the CD133HighCD44High cancer stem cells population, SMAR1 expression is highly diminished leading to elevated hTERT expression. We also find that knockdown of SMAR1 promotes total CD133+CD44+ population and impart enhanced sphere-forming ability to the colorectal cancer cells. SMAR1 also inhibits invasion and metastasis in colorectal cancer cell lines via repression of hTERT. Our study provides evidence that downregulation of SMAR1 causes activation of hTERT leading to an increase in the cancer stem cell phenotype in colorectal cancer cells.

Roles for the 8-Oxoguanine DNA Repair System in Protecting Telomeres From Oxidative Stress.

Telomeres are protective nucleoprotein structures that cap linear chromosome ends and safeguard genome stability. Progressive telomere shortening at each somatic cell division eventually leads to critically short and dysfunctional telomeres, which can contribute to either cellular senescence and aging, or tumorigenesis. Human reproductive cells, some stem cells, and most cancer cells, express the enzyme telomerase to restore telomeric DNA. Numerous studies have shown that oxidative stress caused by excess reactive oxygen species is associated with accelerated telomere shortening and dysfunction. Telomeric repeat sequences are remarkably susceptible to oxidative damage and are preferred sites for the production of the mutagenic base lesion 8-oxoguanine, which can alter telomere length homeostasis and integrity. Therefore, knowledge of the repair pathways involved in the processing of 8-oxoguanine at telomeres is important for advancing understanding of the pathogenesis of degenerative diseases and cancer associated with telomere instability. The highly conserved guanine oxidation (GO) system involves three specialized enzymes that initiate distinct pathways to specifically mitigate the adverse effects of 8-oxoguanine. Here we introduce the GO system and review the studies focused on investigating how telomeric 8-oxoguanine processing affects telomere integrity and overall genome stability. We also discuss newly developed technologies that target oxidative damage selectively to telomeres to investigate roles for the GO system in telomere stability.

Investigation of the Relationship between IgG and Telomerase In Simental Cattle In Different Age Groups

Preservation of telomere length suggests that it can play an active role in avoiding diseases that can be seen with aging and in avoiding cellular aging. Telomeres shorten slightly with each cell division. Telomerase enzyme is responsible for elongation of telomere sequences. Immunoglobulins can be thought of as the molecular structure of antibodies. IgG making up 75-80% of antibodies. The aim of this study is to evaluate the levels of IgG and telomerase enzyme, which have an important place in the immune system with aging. The research material consisted of a total of 46 animals of Simmental breed, 1-day-old 8 calves, 6-month-old 8calves, 1-year-old 8 calves, 4-year-old 12 and 6-year-old 10 cattle in various farms. After the blood samples taken from the animals were centrifuged, their serums were removed and telomerase enzyme levels and IgG levels were measured and compared by ELISA method. As a result, in this study, it was observed that telomerase enzyme activity decreases with aging. While IgG levels did not decrease in the first four groups, a positive correlation was found between IgG and telomerase values in 6-year-old animals. In addition, no significant difference was observed in animals in the same age groups.

Acute Exercise Regulates Htert Alternative Splicing In Contractile Tissues Of Htert-bac Mice

Full length human telomerase reverse transcriptase (FL hTERT) is the rate-limiting, catalytic component necessary for telomerase enzyme activity and telomere length maintenance. Unlike rodents, humans evolved elongated introns with cis-elements that when bound by specific RNA binding proteins (RNAbp) splice hTERT to FL transcripts or produce inactive variants through alternative splicing (AS). Our working hypothesis is that hTERT AS regulates the amount of active telomerase. Evidence from human studies have shown that aerobic exercise maintains telomere length through increased hTERT expression and telomerase enzyme activity, however the impact of acute exercise on hTERT AS is unknown. PURPOSE: To examine hTERT AS regulation in response to acute treadmill running. METHODS: A bacterial artificial chromosome mouse model containing the full hTERT gene (5' and 3' regulatory elements; 16 exons and 15 introns) inserted into its genome (hTERT-BAC) was utilized. Gastrocnemius (Gas.) and heart (Hrt.) were excised from 10-week old hTERT-BAC mice prior to (PRE), upon cessation (POST), and during recovery (1, 24, 48, and 72H; n = 5/time point) from 30 min. of treadmill running (60% max. speed). Primers specific to hTERT were utilized to measure FL and the most common AS variant minus beta (-β, which skips exons 7 and 8) by two different RT-PCR methods - gel based and droplet digital PCR. Gene expression of the RNAbp PTBP1 was also measured. RESULTS: The expected human patterns of hTERT AS was recapitulated across all tissues examined. Compared to PRE, FL hTERT gene expression increased at POST before decreasing in the Gas. (48 and 72H; p ≤ 0.001) and Hrt. (24H; p = 0.004). Acute exercise also increased the percentage of FL hTERT in the Gas. at 1 and 72H (p ≤ 0.017), whereas a decrease was observed in the Hrt. at 1, 24, and 48H (p ≤ 0.041). Finally, Ptbp1 decreased at POST (Gas.) and at 1, 24, 48, and 72H (Gas. and Hrt.; p ≤ 0.05). CONCLUSIONS: Evolutionarily conserved mouse splicing machinery (RNAbp) recognize hTERT cis-elements to recapitulate human AS patterns and highlight the importance of the intronic elements in regulating hTERT splicing choice in humans. The hTERT-BAC mouse is a valuable resource to study the exercise-induced adaptive mechanisms that maintain telomere lengths in endurance trained individuals across the lifespan.

Camptothecin shows better promise than Curcumin in the inhibition of the Human Telomerase: A computational study

ObjectivesThe Human Telomerase enzyme has become a drug target in the treatment of cancers and age-related disorders. This study aims to identify potential natural inhibitors of the Human Telomerase from compounds derived from edible African plants. Materials and methodsA library of 1,126 natural compounds was molecularly docked against the Telomerase Reverse Transcriptase (PDB ID: 5ugw), the catalytic subunit of the target protein. Curcumin, a known Telomerase inhibitor was used as the standard. The front-runner compounds were screened for bioavailability, pharmacokinetic properties, and bioactivity using the SWISSADME, PKCSM, and Molinspiration webservers respectively. The molecular dynamic simulation and analyses of the apo and holo proteins were performed by the Galaxy supercomputing webserver. ResultsThe results of the molecular docking and virtual screening reveal Augustamine and Camptothecin as lead compounds. Augustamine has better drug-likeness and pharmacokinetic properties while Camptothecin showed better bioactivity and stronger binding affinity (-8.2 kcal/mol) with the target. The holo structure formed by Camptothecin showed greater inhibitory activity against the target with a total RMSF of 169.853, B-Factor of 20.164, and 108 anti-correlating residues. ConclusionThough they both act at the same binding site, Camptothecin induces greater Telomerase inhibition and better molecular stability than the standard, Curcumin. Further tests are required to investigate the inhibitory activities of the lead compounds.

Chemical targeting of G-quadruplexes in telomeres and beyond for molecular cancer therapeutics.

G-quadruplexes (G4s) are higher-order structures formed by guanine-rich sequences of nucleic acids, such as the telomeric 5'-TTAGGG-3'/5'-UUAGGG-3' repeats and those in gene regulatory regions. G4s regulate various biological events, including replication, transcription, and translation. Imbalanced G4 dynamics is associated with diseases, such as cancer and neurodegenerative diseases. Telomestatin is a natural macrocyclic compound derived from Streptomyces anulatus 3533-SV4. It interacts with the guanine quartet via π-π stacking and potently stabilizes G4. Because G4 stabilization at the telomeric repeat inhibits the telomere-synthesizing enzyme telomerase, telomestatin was originally identified as a telomerase inhibitor. Whereas non-toxic doses of telomestatin induce gradual shortening of telomeres and eventual crisis in human cancer cells, higher doses trigger prompt replication stress and DNA damage responses, resulting in acute cell death. Suppression of the transcription and translation of G4-containing genes is also implicated in the anticancer effects of telomestatin. Because telomestatin is rare, labile, and insoluble, synthetic oxazole telomestatin derivatives have been developed and verified for their therapeutic efficacies in preclinical cancer models. Furthermore, a variety of G4-stabilizing compounds have been reported as promising seeds for molecular cancer therapeutics. To improve the design of future clinical studies, it will be important to identify predictive biomarkers of drug efficacy.

Association of the PINX1 Variant rs6984094, Which Lengthens Telomeres, with Systemic Lupus Erythematosus Susceptibility in Chinese Populations.

A recent genome-wide association study (GWAS) of Asian ancestry reported that single nucleotide polymorphism (SNP) in TERT (telomerase reverse transcriptase) was associated with systemic lupus erythematosus (SLE). TERT has a critical role in maintaining the chromosomal stability and the length of telomere. Given that only a small portion of the genetic heritability of SLE has been explained so far, we aimed to identify novel loci in telomere-related genes responsible for SLE susceptibility in Chinese populations. We performed a comprehensive genetic association analysis of SLE with telomere-related genes. To identify functional significance, we analyzed the publicly available HaploReg v4.1 and RegulomeDB databases. Differential gene expression analysis was also performed using ArrayExpress. A novel signal of PINX1 rs6984094 was identified (Pdiscovery = 4.13 × 10−2, OR = 0.58, 95% CI 0.35-0.98) and successfully replicated (Preplication = 5.73 × 10−3, OR = 0.45, 95% CI 0.26-0.81). Multiple layers of functional analysis suggested that the PINX1 rs6984094 risk T allele exhibited increased nuclear protein binding. We also observed an increased expression of PINX1 mRNA in peripheral blood mononuclear cells from SLE patients compared with healthy controls. Overall, we observed a novel genetic association between PINX1 (encodes the PinX1 protein, an inhibitory telomerase enzyme that lengthens telomeres) and SLE susceptibility in Chinese populations.

Telomerase activity can mediate the effects of growth on telomeres during post-natal development in a wild bird.

In wild animals, telomere attrition during early development has been linked with several fitness disadvantages throughout life. Telomerase enzyme can elongate telomeres, but it is generally assumed that its activity is suppressed in most somatic tissues upon birth. However, recent evidence suggests that this may not be the case for long-lived bird species. We have therefore investigated whether telomerase activity is maintained during the postnatal growth period in a wild yellow-legged gull (Larus michahellis) population. Our results indicate that telomerase activity is not negligible in the blood cells, but activity levels sharply decline from hatching to fledging following a similar pattern to the reduction observed in telomere length. Our results further suggest that the observed variation in telomere length may be the result of a negative effect of fast growth on telomerase activity, thus providing a new mechanism through which growth rates may affect telomere dynamics and potentially life-history trajectories.

Gene Expression Profile in Immortalized Human Periodontal Ligament Fibroblasts Through hTERT Ectopic Expression: Transcriptome and Bioinformatic Analysis.

Human periodontal ligament fibroblast (hPLF) cells play an important role in maintaining oral cavity homeostasis with special function in tissue regeneration and maintenance of dental alveoli. Although their primary cell cultures are considered a good experimental model with no genetic changes, the finite life span may limit some experimental designs. The immortalization process increases cell life span but may cause genetic changes and chromosomal instability, resulting in direct effects on physiological cell responses. In this way, we aimed to investigate the global gene expression of hPLFs after the immortalization process by the ectopic expression of the catalytic subunit of the enzyme telomerase reverse transcriptase (hTERT) through transcriptome analysis. The embryonic origin of the primary culture of hPLF cells and immortalized hPLF-hTERT was also tested by vimentin staining, hTERT synthesis evaluated by indirect immunocytochemistry, analysis of cell proliferation, and morphology. The results indicated that hPLFs and hPLF-hTERT were positive for vimentin. On the 20th cell passage, hPLFs were in senescence, while hPLF-hTERT maintained their proliferation and morphology characteristics. At the same passage, hPLF-hTERT presented a significant increase in hTERT synthesis, but transcriptome did not reveal overexpression of the hTERT gene. Fifty-eight genes had their expression altered (11 upregulated and 47 downregulated) with the absence of changes in the key genes related to these cell types and in the main cancer-associated genes. In addition, the increase in hTERT protein expression without the overexpression of its gene indicates posttranscriptional level regulation. Successful immortalization of hPLFs through the ectopic expression of hTERT encourages further studies to design experimental protocols to investigate clinical questions from a translational perspective.