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Inflammation underlies most age-related diseases, including cancer, but the etiology is poorly understood. One proposed factor is the presence of senescent cells, which increase with age. The senescence response arrests the proliferation of potentially oncogenic cells, and most senescent cells secrete high levels of proinflammatory cytokines and other proteins. The complex senescence-associated secretory phenotype is likely regulated at multiple levels, most of which are unknown. We show that cell surface-bound IL-1alpha is essential for signaling the senescence-associated secretion of IL-6 and IL-8, 2 proinflammatory cytokines that also reinforce the senescence growth arrest. Senescent human fibroblasts expressed high levels of IL-1alpha mRNA, intracellular protein, and cell surface-associated protein, but secreted very little protein. An IL-1 receptor (IL1R) antagonist, neutralizing IL-1alpha antibodies, and IL-1alpha depletion by RNA interference all markedly reduced senescence-associated IL-6/IL-8 secretion. Depletion of the key IL-1R signaling component IRAK1 also suppressed this secretion, and IL-1alpha neutralizing antibodies prevented IRAK1 degradation, indicating engagement of the IL-1R signaling pathway. Furthermore, IL-1alpha depletion reduced the DNA binding activity of NF-kappaB and C/EBPbeta, which stimulate IL-6/IL-8 transcription. IL-1alpha was a general regulator of senescence-associated IL-6/IL-8 secretion because IL-1alpha blockade reduced IL-6/IL-8 secretion whether cells senesced owing to DNA damage, replicative exhaustion, oncogenic RAS, or chromatin relaxation. Furthermore, conditioned medium from IL-1alpha-depleted senescent cells markedly reduced the IL-6/IL-8-dependent invasiveness of metastatic cancer cells, indicating that IL-1alpha regulates the biological effects of these cytokines. Thus, cell surface IL-1alpha is an essential cell-autonomous regulator of the senescence-associated IL-6/IL-8 cytokine network.

Nuclear pores span the nuclear envelope and act as gated aqueous channels to regulate the transport of macromolecules between the nucleus and cytoplasm, from individual proteins and RNAs to entire viral genomes. By far the largest subunit of the nuclear pore is the Nup107–160 complex, which consists of nine proteins and is critical for nuclear pore assembly. At mitosis, the Nup107–160 complex localizes to kinetochores, suggesting that it may also function in chromosome segregation. To investigate the dual roles of the Nup107–160 complex at the pore and during mitosis, we set out to identify binding partners by immunoprecipitation from both interphase and mitotic Xenopus egg extracts and mass spectrometry. ELYS, a putative transcription factor, was discovered to copurify with the Nup107–160 complex in Xenopus interphase extracts, Xenopus mitotic extracts, and human cell extracts. Indeed, a large fraction of ELYS localizes to the nuclear pore complexes of HeLa cells. Importantly, depletion of ELYS by RNAi leads to severe disruption of nuclear pores in the nuclear envelope, whereas lamin, Ran, and tubulin staining appear normal. At mitosis, ELYS targets to kinetochores, and RNAi depletion from HeLa cells leads to an increase in cytokinesis defects. Thus, we have identified an unexpected member of the nuclear pore and kinetochore that functions in both pore assembly at the nucleus and faithful cell division.