Regulation of the senescence-associated secretory phenotype by the nucleoporin TPR

Trabajo presentado en el yICSA Senescence Symposium, celebrado en Londres (Inglaterra) el 29 de abril de 2022.Oncogene-induced senescence is a state of irreversible cell cycle arrest, accompanied by the secretion of signalling molecules, including pro-inflammatory cytokines and chemokines. These are known as the senescence-associated secretory phenotype (SASP). We previously showed that the nucleoporin TPR is necessary for SASP induction in senescent IMR90 fibroblasts with an inducible Ras(G12V) mutation. TPR is a protein in the nuclear basket, which is anchored to the nuclear pore complex. We used ATAC-seq to identify potential enhancer elements which become accessible in senescent cells, but where this chromatin accessibility is lost when TPR is knocked down. These putative enhancers are enriched in binding sites for NF-κ-B, a transcription factor known to regulate the SASP. Using immunofluorescence, we show that NF-κ-B activation is indeed reduced in senescent cells lacking TPR. This decrease in NF-κ-B activation precedes the SASP, suggesting it occurs upstream. In addition, TPR depletion in senescent cells leads to reduced levels of cytoplasmic chromatin fragments (CCFs). These CCFs are known to activate NF-κ-B and the SASP through cGAS-STING signalling, suggesting a potential mechanism for the loss of SASP in senescent cells without TPR. It remains to be determined how perturbation at nuclear pores affects the formation of CCFs in senescent cells