Acute depletion of telomerase components DKC1 and NOP10 induces oxidative stress and disrupts ribosomal biogenesis via NPM1 and activation of the P53 pathway

Mutations in DKC1, NOP10, and TINF2 genes, coding for proteins in telomerase and shelterin complexes, are responsible for diverse diseases known as telomeropathies and ribosomopathies, including dyskeratosis congenita (DC, ORPHA 1775). These genes contribute to the DC phenotype through mechanisms that are not completely understood. We previously demonstrated in models of DC that oxidative stress is an early and independent event that occurs prior to telomere shortening. To clarify the mechanisms that induce oxidative stress, we silenced genes DKC1, NOP10, and TINF2 with siRNA technology. With RNA array hybridisation, we found several altered pathways for each siRNA model. Afterwards, we identified common related genes. The silenced cell line with the most deregulated genes and pathways was siNOP10, followed by siDKC1, and then by siTINF2 to a lesser extent. The siDKC1 and siNOP10 models shared altered expression of genes in the p53 pathway, while siNOP10 and siTINF2 had the adherens junction pathway in common. We also observed that depletion of DKC1 and NOP10 H/ACA ribonucleoprotein produced ribosomal biogenesis impairment which, in turn, promoted p53 pathway activation. Finally, we found that those enzymes responsible for GSH synthesis were down-regulated in models of siDKC1 and siNOP10. In contrast, the silenced cells for TINF2 showed no disruption of ribosomal biogenesis or oxidative stress and did not produce p53 pathway activation. These results indicate that depletion of DKC1 and NOP10 promotes oxidative stress and disrupts ribosomal biogenesis which, in turn, activates the p53 pathway.