Human telomeres are protected from DNA damage by a nucleoprotein complex that includes the repeat-binding factor TRF2. Here, we report that TRF2 regulates the 5' exonuclease activity of its binding partner, Apollo, a member of the metallo-beta-lactamase family that is required for telomere integrity during S phase. TRF2 and Apollo also suppress damage to engineered interstitial telomere repeat tracts that were inserted far away from chromosome ends. Genetic data indicate that DNA topoisomerase 2alpha acts in the same pathway of telomere protection as TRF2 and Apollo. Moreover, TRF2, which binds preferentially to positively supercoiled DNA substrates, together with Apollo, negatively regulates the amount of TOP1, TOP2alpha, and TOP2beta at telomeres. Our data are consistent with a model in which TRF2 and Apollo relieve topological stress during telomere replication. Our work also suggests that cellular senescence may be caused by topological problems that occur during the replication of the inner portion of telomeres.

Aims: Depression is prevalent among university students worldwide, and the prevalence appears to be increasing. As an intermediate stage between being healthy and having depression, students with subthreshold depression could develop worsening depression or recover with intervention to prevent depression. The Center for Epidemiologic Studies Depression Scale (CES-D) is a useful tool to assess subthreshold depression. The primary purpose of the current study was to evaluate the psychometric characteristics of CES-D in Chinese university students. Secondly, we aimed to describe the prevalence of subthreshold depression among the student sample and examine its demographic correlates. Methods: A total of 2,068 university students participated in the study, and they were asked to respond to the Chinese CES-D, Beck Depression Inventory-II (BDI-II), and Positive and Negative Affect Schedule (PANAS). The factor structure was evaluated by conducting exploratory (EFA) and confirmatory factor analysis (CFA) using a structural equation modeling approach. The reliability was assessed by calculating Cronbach’s alpha, inter-item correlation, and item-total correlation coefficients. The prevalence of subthreshold depression was calculated and demographic correlates of gender, grade, and major were examined by multiple regression. Results: The final sample included 1,920 participants. The EFA results suggested extraction of three factors (somatic symptoms, negative affect, and anhedonia) that account for 52.68% of total variance. The CFA results suggested that the newly derived model with 14 items was the best fit for our data. Six items were removed from the original scale (item 9, 10, 13, 15, 17, and 19). The Cronbach’s alpha of the 14-item CES-D was 0.87. The prevalence of subthreshold depression among university students reached 32.7% for the 20-item CES-D and 31% for the 14-item CES-D, although there was no significant difference of prevalence in gender, grade, and major. Conclusions: The CES-D has good reliability and validity for assessing subthreshold depression in Chinese university students.

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Serum IL-33 may be a useful biomarker for predicting the prognosis of gastric cancer.