Mitochondrial dysfunctions play major roles in ageing. How mitochondrial stresses invoke downstream responses and how specificity of the signaling is achieved, however, remains unclear. We have previously discovered that the RNA component of Telomerase TERCis imported into mitochondria, processed to a shorter form TERC-53, and then exported back to the cytosol. Cytosolic TERC-53levels respond to mito- chondrial functions, but have no direct effect on these functions, suggesting that cytosolic TERC-53functions downstream of mitochondria as a signal of mitochon- drial functions. Here, we show that cytosolic TERC-53plays a regulatory role on cellular senescence and is involved in cognition decline in 10 months old mice, independent of its telomerase function. Manipulation of cytosolic TERC-53levels affects cellular senescence and cognition decline in 10 months old mouse hip-pocampi without affecting telomerase activity, and most importantly, affects cellular senescence in terc−/− cells. These findings uncover a senescence-related regulatory pathway with a non-coding RNA as the signal in mammals.
RAP1 is a well-known telomere-binding protein, but its functions in human stem cells have remained unclear. Here we generated RAP1-deficient human embryonic stem cells (hESCs) by using CRISPR/Cas9 technique and obtained RAP1-deficient human mesenchymal stem cells (hMSCs) and neural stem cells (hNSCs) via direc- ted differentiation. In both hMSCs and hNSCs, RAP1 not only negatively regulated telomere length but also acted as a transcriptional regulator of RELN by tuning the methylation status of its gene promoter. RAP1 defi- ciency enhanced self-renewal and delayed senescence in hMSCs, but not in hNSCs, suggesting complicated lineage-specific effects of RAP1 in adult stem cells. Altogether, these results demonstrate for the first time that RAP1 plays both telomeric and nontelomeric roles in regulating human stem cell homeostasis.
Human embryonic stem cells (hESCs) depend on glycolysis for energy and substrates for biosynthesis. To understand the mechanisms governing the metabolism of hESCs, we investigated the transcriptional regulation of glucose transporter 1 (GLUT1, SLC2A1), a key glycolytic gene to maintain pluripotency. By combining the genome-wide data of binding sites of the core pluripotency factors (SOX2, OCT4, NANOG, denoted SON), chromosomal interaction and histone modification in hESCs, we identified a potential enhancer of the GLUT1 gene in hESCs, denoted GLUT1 enhancer (GE) element. GE interacts with the promoter of GLUT1, and the deletion of GE significantly reduces the expression of GLUT1, glucose uptake and glycolysis of hESCs, confirming that GE is an enhancer of GLUT1 in hESCs. In addition, the mutation of SON binding motifs within GE reduced the expression of GLUT1 as well as the interaction between GE and GLUT1 promoter, indicating that the binding of SON to GE is important for its activity. Therefore, SON promotes glucose uptake and glycolysis in hESCs by inducing GLUT1 expression through directly activating the enhancer of GLUT1.
