Aggregation-Induced Enhanced Electrochemiluminescence from Tris(bipyridine)ruthenium(II) Derivative Nanosheets for the Ultrasensitive Detection of Human Telomerase RNA.

The traditional tris(bipyridine)ruthenium(II) complex suffers from the notorious aggregation-caused quenching effect, which greatly compromises its electrochemiluminescence (ECL) efficiency, thus hindering further applications in biosensing and clinical diagnosis. Here, the ultrathin tetraphenylethylene-active tris(bipyridine)ruthenium(II) derivative nanosheets (abbreviated as Ru-TPE NSs) are synthesized through a protein-assisted self-assembly strategy for ultrasensitive ECL detection of human telomerase RNA (hTR) for the first time. The synthesized Ru-TPE NSs exhibit the aggregation-induced enhanced ECL behavior and excellent water-dispersion. Surprisingly, up to a 106.5-fold increase in the ECL efficiency of Ru-TPE NSs is demonstrated compared with the dispersed molecules in an organic solution. The restriction of intramolecular motions is confirmed to be responsible for the significant ECL enhancement. Therefore, this proposed ECL biosensor shows high sensitivity and excellent selectivity for hTR based on Ru-TPE NSs as efficient ECL beacons and the catalytic hairpin assembly as signal amplification, whose detection limit is as low as 8.0 fm, which is far superior to the previously reported works. Here, a promising analytical method is provided for early clinical diagnosis and a new type of efficient ECL emitters with great application prospects is represented.

Regulation of poly(a)-specific ribonuclease activity by reversible lysine acetylation.

Poly(A)-specific ribonuclease (PARN) is a 3'-exoribonuclease that plays an important role in regulating the stability and maturation of RNAs. Recently, PARN has been found to regulate the maturation of the human telomerase RNA component (hTR), a noncoding RNA required for telomere elongation. Specifically, PARN cleaves the 3'-end of immature, polyadenylated hTR to form the mature, nonpolyadenylated template. Despite PARN's critical role in mediating telomere maintenance, little is known about how PARN's function is regulated by post-translational modifications. In this study, using shRNA- and CRISPR/Cas9-mediated gene silencing and knockout approaches, along with 3'-exoribonuclease activity assays and additional biochemical methods, we examined whether PARN is post-translationally modified by acetylation and what effect acetylation has on PARN's activity. We found PARN is primarily acetylated by the acetyltransferase p300 at Lys-566 and deacetylated by sirtuin1 (SIRT1). We also revealed how acetylation of PARN can decrease its enzymatic activity both in vitro, using a synthetic RNA probe, and in vivo, by quantifying endogenous levels of adenylated hTR. Furthermore, we also found that SIRT1 can regulate levels of adenylated hTR through PARN. The findings of our study uncover a mechanism by which PARN acetylation and deacetylation regulate its enzymatic activity as well as levels of mature hTR. Thus, PARN's acetylation status may play a role in regulating telomere length.

Regulation of human telomerase RNA biogenesis and localization.

Maintenance of telomeres is essential for genome integrity and replicative capacity in eukaryotic cells. Telomerase, the ribonucleoprotein complex that catalyses telomere synthesis is minimally composed of a reverse transcriptase and an RNA component. The sequence and structural domains of human telomerase RNA (hTR) have been extensively characterized, while the regulation of hTR transcription, maturation, and localization, is not fully understood. Here, we provide an up-to-date review of hTR, with an emphasis on current breakthroughs uncovering the mechanisms of hTR maturation and localization.

Differential shortening rate of telomere length in the development of human fetus.

Telomeres play an important role in the maintenance of genomic stability/integrity and are synthesized by the RNA-dependent polymerase telomerase. Progressive telomere shortening contributes to both in vitro and in vivo aging, and telomere length dynamics and telomerase expression profile in human tissues during extrauterine life have been well characterized. However, little is known about these changes in the early stage of gestation. In the present study, we determined telomere length and the expression of telomerase core units (telomerase reverse transcriptase, hTERT, and telomerase RNA component, hTERC) in human fetus tissues from 6 to 11 weeks of gestational age. A sharp decline in telomere length occurred between 6 and 7 weeks of gestational age, and a relatively stable or slightly shortened telomere length was thereafter maintained until birth. The inverse correlation between TERT or TERC expression and gestational age was steadily observed in these fetus tissues. Taken together, there is a rapid reduction followed by a slow erosion of telomere length in human fetus from gestational age 6-11 weeks, while hTERT and hTERC expression decreases steadily during this period. The present findings not only contribute to better understandings of telomere/telomerase biology in human embryonic development, but also are implicated in telomere/telomerase-related diseases or problems.

Viral and cellular telomerase RNAs possess host-specific anti-apoptotic functions.

Human telomerase RNA (hTR) is overexpressed in many cancers and protects T cells from apoptosis in a telomerase-independent manner. The most prevalent cancer in the animal kingdom is caused by the highly oncogenic herpesvirus Marek's disease virus (MDV). MDV encodes a viral telomerase RNA (vTR) that plays a crucial role in MDV-induced tumorigenesis and shares all four conserved functional domains with hTR. In this study, we assessed whether hTR drives tumor formation in this natural model of herpesvirus-induced tumorigenesis. Therefore, we replaced vTR with hTR in the genome of a highly oncogenic MDV. Furthermore, we investigated the anti-apoptotic activity of vTR, hTR, and their counterpart in the chicken [chicken telomerase RNA (cTR)]. hTR was efficiently expressed and did not alter replication of the recombinant virus. Despite its conserved structure, hTR did not complement the loss of vTR in virus-induced tumorigenesis. Strikingly, hTR did not inhibit apoptosis in chicken cells, but efficiently inhibited apoptosis in human cells. Inverse host restriction has been observed for vTR and cTR in human cells. Our data revealed that vTR, cTR, and hTR possess conserved but host-specific anti-apoptotic functions that likely contribute to MDV-induced tumorigenesis. IMPORTANCE hTR is overexpressed in many cancers and used as a cancer biomarker. However, the contribution of hTR to tumorigenesis remains elusive. In this study, we assessed the tumor-promoting properties of hTR using a natural virus/host model of herpesvirus-induced tumorigenesis. This avian herpesvirus encodes a telomerase RNA subunit (vTR) that plays a crucial role in viral tumorigenesis and shares all conserved functional domains with hTR. Our data revealed that vTR and cellular TRs of humans and chickens possess host-specific anti-apoptotic functions. This provides important translational insights into therapeutic strategies, as inhibition of apoptosis is crucial for tumorigenesis.

In vitro characterization and rational analog design of a novel inhibitor of telomerase assembly in MDA MB 231 breast cancer cell line.

Tumor cells have unlimited replicative potential, principally due to telomerase activity, which requires assembly of components such as dyskerin (hDKC1), human telomerase reverse transcriptase and human telomerase RNA (hTR). The present study aimed to develop novel inhibitors of telomerase to target the interaction between hTR and hDKC1. Based on docking­based virtual screening, the candidates R1D2­10 and R1D2­15, which exert an in vitro inhibitory effect on telomerase activity, were selected. Human mammary adenocarcinoma MDA­MB 231 cell line was selected to evaluate the treatment with the aforementioned compounds; the effect on telomere length was evaluated by qPCR, where both compounds caused telomere shortening. Furthermore, expression of genes related to apoptosis and senescence process, as well SA ß galactosidase staining and caspase 3 activity. We determine that only compound R1D2­10 showed and effect on the induction of these cellular processes. To identify a lead compound from R1D2­10, 100 analogs were designed by LigDream server and then analyzed by AutoDock Vina and Protein­Ligand Interaction Profile to calculate their docking energy and target interaction. Those with the best values and specific residue interactions were selected for in silico prediction of absorption, distribution, metabolism, excretion (ADME), off­target interaction, toxicity and chemical diversity. A total of nine chemically different analogs was identified with higher docking affinity to the target, suitable ADME properties and not off­target interaction and side effects. These results indicated R1D2­10 and its analogs may serve as potential novel inhibitors of telomerase and antitumoral drugs in clinical use.

A pH-responsive colorimetric detection of human telomerase RNA based on a three-dimensional DNA amplifier.

Human telomerase RNA (hTR), one of the essential components of telomerase, serves as a reverse template to add repeated segments of (TTAGGG)n to the 3' end of telomere DNA for maintaining the length of telomere DNA, endowing cells indefinite proliferation capability. Expression level of hTR displays a close relationship with tumor grade. Inspired by the mechanism of urease hydrolyzing urea to release ammonia and elevate the pH value of the sample solution, we developed a facile and novel pH-responsive colorimetric strategy for hTR detection by incorporating catalyzed hairpin assembly (CHA) onto the magnetic beads (MBs). The CHA process was initiated by target hTR and recycled via toehold binding and branch migration, thereby abundant urease being anchored on the surface of MBs. After separated by an external magnetic field, the assembled urease catalyzed the hydrolysis of urea to release a large amount of ammonia, which gave rise to a remarkable pH signal. Thus, quantification of hTR was achieved by measuring the solution pH via a hand-held pH meter or visualizing the solution color with the assistance of the pH indicator phenol red. The proposed sensing platform exhibits excellent performance toward hTR with a detection limit as low as 41 pM and a remarkable sequence selectivity, being able to differentiate a single mismatch in the target DNA. The pH-responsive colorimetric sensing platform contributes to introducing pH-related portable strategies into the detections of numerous universal biomarkers such as nucleic acids and proteins.

Quantitative assessment of telomerase components in cancer cell lines.

Besides its canonical function of catalyzing the formation of telomeric repeats, many groups have recently reported non-canonical functions of hTERT in particular, and telomerase in general. Regulating transcription is the central basis of non-canonical functions of telomerase. However, unlike reverse transcriptase activity of telomerase that requires only a few molecules of enzymatically active hTERT, non-canonical functions of hTERT or other telomerase components theoretically require several hundred copies. Here, we provide the first direct quantification of all the telomerase components in human cancer cell lines. We demonstrate that telomerase components do not exist in a 1:1 stoichiometric ratio, and there are several hundred copies of hTERT in cells. This provides the molecular basis of hTERT to function in other signaling cascades, including transcription.

Gain of hTERC: a genetic marker of malignancy in oral potentially malignant lesions.

Oral squamous cell carcinoma (OSCC) is the most common oral cancer, and major efforts is being made to identify molecular markers capable to differentiate oral potentially malignant lesions (OPMLs) with indolent course from lesions with aggressive behavior. We undertook a study to evaluate if gain of the human telomerase RNA component (hTERC) gene in OPMLs could indicate lesions at high risk of developing OSCC. The study was performed on 30 OPMLs with long-term follow-up using a dual-color interphase fluorescence in situ hybridization (FISH) for hTERC status. Progression to malignancy was observed in 9 of 10 cases harboring hTERC gain and in 1 of 20 cases retaining a normal copy number of hTERC (P < .0001). Combining morphological grading and FISH analysis, all the cases with high-grade squamous intraepithelial lesion or carcinoma in situ harboring hTERC amplification progressed to OSCC, whereas none of the low-grade squamous intraepithelial lesions without hTERC gain progressed. Intermediate situations occurred. The data suggest that precise morphological evaluation together with FISH assessment for hTERC gain might pave the way to stratify OPMLs into high-risk and low-risk categories and could be helpful in selecting the most appropriate treatment.

Detention of HPV L1 Capsid Protein and hTERC Gene in Screening of Cervical Cancer.

OBJECTIVE(S): To investigate the expression of human papilloma virus (HPV) L1 capsid protein, and human telomerase RNA component (hTERC) in cervical cancer and the role of detection of both genes in screening of cervical cancer. MATERIALS AND METHODS: A total of 309 patients were recruited and cervical exfoliated cells were collected. Immunocytochemistry was employed to detect HPV L1 capsid protein, and fluorescent in situ hybridization (FISH) was performed to detect the hTERC. RESULTS: The expression of HPV L1 capsid protein reduced with the increase of the histological grade of cervical cells and was negatively related to the grade of cervical lesions. However, the expression of hTERC increased with the increase of the histological grade and positively associated with the grade of cervical lesions. The proportion of patients with L1(-)/hTERC(+) was higher in patients with histological grade of CIN2 or higher than that in those with histological grade of CIN1. The L1(+)/hTERC(-) and L1(-)/hTERC(-) were negatively related to the grade of cervical lesions. L1(-)/hTERC(+) was positively associated with the grade of cervical lesions. The L1/hTERC ratio increased. The negative predictive value of both HPV L1 and hTERC was higher than that of HPV L1 or hTERC, but there was no marked difference in the screening efficacy of cervical cancer among HPV L1, hTERC and HPV L1+hTERC. CONCLUSION: HPV L1 capsid protein and hTERC gene may serve as markers for the early diagnosis and prediction of cervical lesions. The increase in L1/hTERC ratio reflects the progression of cervical lesions to a certain extent.