Telomerase activity is elevated in most cancer cells and is required for telomere length maintenance and immortalization of cancer cells. Glucose metabolic reprogramming is a hallmark of cancer and accompanied with increased expression of key metabolic enzymes. Whether these enzymes influence telomerase activity and cell immortalization remains unclear. In the current study, we screened metabolic enzymes using telomerase activity assay and identified lactate dehydrogenase B (LDHB) as a regulator of telomerase activity. Sodium lactate and sodium pyruvate did not influence telomerase activity, indicating LDHB regulates telomerase activity independent of its metabolism regulating function. Further studies revealed that LDHB directly interacted with TERT and regulated the interaction between TERT and TERC. Additionally, long-term knockdown of LDHB inhibited cancer cell growth and induced cell senescence in vitro and in vivo. Higher LDHB expression was detected in pancreatic cancer tissues compared with that in adjacent normal tissues and expression of LDHB correlated negatively with prognosis. Thus, we identified LDHB as the first glucose metabolic enzyme contributing to telomerase activity and pancreatic cancer cell immortalization.
Background Telomerase is a ribonucleoprotein enzyme responsible for maintenance of telomere length which expressed in more than 85% of cancer cells but undetectable in most normal tissue cells. Therefore, telomerase serves as a diagnostic marker of cancers. Two commonly used telomerase activity detection methods, the telomerase repeated amplification protocol (TRAP) and the direct telomerase assay (DTA), have disadvantages that mainly arise from reliance on PCR amplification or the use of an isotope. A safe, low‐cost and reliable telomerase activity detection method is still lacking. Method We modified DTA method using biotin‐labeled primers (Biotin‐DTA) and optimized the method by adjusting cell culture temperature and KCl concentration. The sensitivity of the method was confirmed to detect endogenous telomerase activity. The reliability was verified by detection of telomerase activity of published telomerase regulators. The stability was confirmed by comparing the method with TRAP method. Results Cells cultured in 32°C and KCl concentration at 200 mM or 250 mM resulted in robust Biotin‐DTA signal. Endogenous telomerase activity can be detected, which suggested an similar sensitivity as DTA using radioactive isotope markers. Knockdown of telomerase assembly regulator PES1 and DKC1 efficiently reduced telomerase activity. Compared with TRAP method, Biotin‐DTA assay offers greater signal stability over a range of analyte protein amounts. Conclusion Biotin‐labeled, PCR‐free, and nonradioactive direct telomerase assay is a promising new method for the easy, low‐cost, and quantitative detection of telomerase activity.
Coronavirus disease 2019 (COVID-19), caused by coronavirus SARS-CoV-2, is known to disproportionately affect older individuals. Age is the most important determinant of disease severity and mortality. How aging processes affect the disease progression remains largely unknown. Here we found that DNA damage, a common denominator and major cause of aging, promoted susceptibility to SARS-CoV-2 infection in cells and intestinal organoids. SARS-CoV-2 entry was facilitated by DNA damage caused by either telomere attrition or extrinsic genotoxic stress and hampered by inhibition of DNA damage response. Mechanistic analysis revealed that the DNA damage response increased expression of ACE2, the receptor of SARS-CoV-2, by activation of transcription factor c-Jun in vitro and in vivo. Knockdown of c-Jun significantly reduced cell susceptibility to SARS-CoV-2. To explore the clinical clues of contribution of DNA damage in SARS-CoV-2 infection, we analyzed the expression of ACE2, γH2Ax and p-c-Jun in old and young human and mouse tissues. Expression of ACE2 was elevated in older human and mouse tissues and positively correlated with γH2Ax and p-c-Jun. Finally, targeting DNA damage by increasing the DNA repair capacity, alleviated cell susceptibility to SARS-CoV-2. Our data provide insight into the age-associated differences in SARS-CoV-2 infection and a novel target for anti-viral intervention.
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