Telomerase reverse transcriptase (TERT) and the non-coding telomerase RNA subunit (TR) constitute the core of telomerase. Here we now report that the putative F-box protein Pof8 is also a constitutive component of active telomerase in fission yeast. Pof8 functions in a hierarchical assembly pathway by promoting the binding of the Lsm2-8 complex to telomerase RNA, which in turn promotes binding of the catalytic subunit. Loss of Pof8 reduces TER1 stability, causes a severe assembly defect, and results in critically short telomeres. Structure profile searches identified similarities between Pof8 and telomerase subunits from ciliated protozoa, making Pof8 next to TERT the most widely conserved telomerase subunits identified to date.

The conserved shelterin complex is critical for chromosome capping and maintaining telomere length homeostasis. In fission yeast, shelterin is comprised of five proteins. Taz1, Rap1, and Poz1 function as negative regulators of telomere elongation, whereas Pot1 and Tpz1 are critical for end capping and telomerase recruitment. How the five proteins work together to safeguard chromosome ends and promote telomere length homeostasis is a matter of great interest. Using a combination of deletions, fusions, and tethers, we define key elements of shelterin important for telomere length regulation. Surprisingly, deletion of the entire Rap1 and Poz1 proteins does not impair telomere length regulation as long as a static bridge is provided between Taz1 and Tpz1. Cells harboring minishelterin display wild-type telomere length and intact subtelomeric silencing. However, protection against end fusions in G1 is compromised in the absence of Rap1. Our data reveal a remarkable plasticity in shelterin architecture and separate functions in length regulation and end protection.

The expression profile of seven lncRNAs can effectively predict ER after surgical resection for HCC.

Background: Tumor mutational burden (TMB) has emerged as an independent biomarker to predict patient responses to treatment with immune checkpoint inhibitors (ICIs) for lung adenocarcinoma (LUAD). MicroRNAs (miRNAs) have a crucial role in the regulation of anticancer immune responses, but the association of miRNA expression patterns and TMB is not clear in LUAD. Methods: Differentially expressed miRNAs in samples with high TMB and low TMB samples were screened in the LUAD dataset in The Cancer Genome Atlas. The least absolute shrinkage and selection operator (LASSO) method was applied to develop a miRNA-based signature classifier for predicting TMB levels in the training set. An test set was used to validate this classifier. The correlation between the miRNA-based classifier index and the expression of three immune checkpoints (PD-1, PD-L1, and CTLA-4) were explored. Functional enrichment analysis was carried out of the miRNAs included in the miRNAbased signature classifier. Results: Twenty-five differentially expressed miRNAs were used to establish a miRNA-based signature classifier for predicting TMB level. The accuracy of the 25-miRNA-based signature classifier was 0.850 in the training set, 0.810 in the test set and 0.840 in the total set. This miRNA-based signature classifier index showed a low correlation with PD-1 and PD-L1, and no correlation with CTLA-4. Enrichment analysis for these 25 miRNA revealed they are involved in many immune-related biological processes and cancer-related pathways. Conclusion: MiRNA expression patterns are associated with tumor mutational burden and a miRNAbased signature classifier may serve as a biomarker for prediction of TMB levels in LUAD.