Expression of Cellular and Extracellular TERRA, TERC and TERT in Hepatocellular Carcinoma

Non-coding RNAs are transcribed from telomeres and the telomeric repeat-containing RNAs (TERRA) are implicated in telomere homeostasis and in cancer. In this study, we aimed to assess in hepatocellular carcinoma (HCC) the cellular and extracellular expression of TERRA, the telomerase RNA subunit (TERC) and the telomerase catalytic subunit (TERT). We determined by qPCR the expression level of TERRA 1_2_10_13q, TERRA 15q, TERRA XpYp, TERC and of TERT mRNA in HCC tissues and in the plasma of HCC patients. Further, we profiled the same transcripts in the HCC cell lines, HA22T/VGH and SKHep1C3, and in the extracellular vesicles (EVs) derived from their secretomes. We found that the expression of TERRA and TERT mRNA was significantly deregulated in HCC, being TERRA downregulated and TERT mRNA upregulated in HCC tissues vs. the peritumoral (PT) ones, and the receiver operating characteristic (ROC) curve analyses revealed a significant ability in discriminating HCC from PT tissue. Further, the determinations of circulating TERRA and TERC showed higher amounts of these transcripts in the plasma of HCC patients vs. controls and ROC analyses gave significant results. The expression characterization of the cultured HCC cells showed their ability to produce and secrete TERRA and TERC into the EVs; the ability to produce TERT mRNA that was not detectable in the EVs; and the ability to respond to sorafenib treatment increasing TERRA expression. Our results highlight that: (i) both cellular and extracellular expressions of TERRA and TERC are dysregulated in HCC as well as the cellular expression of TERT mRNA and (ii) the combined detection of TERRA and TERC in plasma may represent a promising approach for non-invasive diagnostic molecular indicators of HCC

Identification of telomerase RNAs in species of the Yarrowia Clade provides insights into the co-evolution of telomerase, telomeric repeats and telomere-binding proteins

Telomeric repeats in fungi of the subphylum Saccharomycotina exhibit great inter- and intra-species variability in length and sequence. Such variations challenged telomeric DNA-binding proteins that co-evolved to maintain their functions at telomeres. Here, we compare the extent of co-variations in telomeric repeats, encoded in the telomerase RNAs (TERs), and the repeat-binding proteins from 13 species belonging to the Yarrowia Glade. We identified putative TER loci, analyzed their sequence and secondary structure conservation, and predicted functional elements. Moreover, in vivo complementation assays with mutant TERs showed the functional importance of four novel TER substructures. The TER-derived telomeric repeat unit of all species, except for one, is 10 bp long and can be represented as 5'-TTNNNNAGGG-3', with repeat sequence variations occuring primarily outside the vertebrate telomeric motif 5'-TTAGGG-3'. All species possess a homologue of the Yarrowia lipolytica Tay1 protein, YlTay1p. In vitro, YlTay1p displays comparable DNA-binding affinity to all repeat variants, suggesting a conserved role among these species. Taken together, these results add significant insights into the co-evolution of TERs, telomeric repeats and telomere-binding proteins in yeasts