Transcriptional repression of NFKBIA triggers constitutive IKK‐ and proteasome‐independent p65/RelA activation in senescence

Abstract

The IjB kinase (IKK)-NF-jB pathway is activated as part of the DNA damage response and controls both inflammation and resistance to apoptosis. How these distinct functions are achieved remained unknown. We demonstrate here that DNA double-strand breaks elicit two subsequent phases of NF-jB activation in vivo and in vitro, which are mechanistically and functionally distinct. RNA-sequencing reveals that the first-phase controls anti-apoptotic gene expression, while the second drives expression of senescence-associated secretory phenotype (SASP) genes. The rapidly activated first phase is driven by the ATM-PARP1-TRAF6-IKK cascade, which triggers proteasomal destruction of inhibitory IjBa, and is terminated through IjBa re-expression from the NFKBIA gene. The second phase, which is activated days later in senescent cells, is on the other hand independent of IKK and the proteasome. An altered phosphorylation status of NF-jB family member p65/ RelA, in part mediated by GSK3b, results in transcriptional silencing of NFKBIA and IKK-independent, constitutive activation of NF-jB in senescence. Collectively, our study reveals a novel physiological mechanism of NF-jB activation with important implications for genotoxic cancer treatment.

NF-κB determines Paneth versus goblet cell fate decision in the small intestine

“…n =3 per group, n ≥20 crypts per mouse. (E) Representative IHC images of anti-cleaved caspase 3 and Alcian Blue staining on PSI sections of Δ N and control ( n =3 per group) mice, and of a tissue sample of γ-irradiated control mice (see Kolesnichenko et al, 2021 ). Black arrows point to caspase 3-positive (apoptotic) cells in villi of irradiated controls.…”

NF‐κB/IKK activation by small extracellular vesicles within the SASP

“…However, our results show an increase in IKK mRNA using different housekeeping genes with no significant differences between their expressions in the various experimental conditions, suggesting a transcriptional regulation upon treatment with the evSASP. Interestingly, a recent study has shown that during the initial activation of senescence, IKKβ is activated by ATM while in the later stages the sSASP is expressed independently of IKKα/β and proteasome degradation of IκB in spite of depending on the NF‐κB protein p65 (Kolesnichenko et al, 2021). Altogether, this suggests that the activation of NF‐κB is far more complicated than initially thought in the context of senescence and both the sSASP and evSASP.…”

A New Gene Set Identifies Senescent Cells and Predicts Senescence-Associated Pathways Across Tissues

“…[56][57][58][59][60][61][62][63] Interestingly, the control of the SASP itself by RELA/p65, which we detected in two sequencing datasets of aging women, has recently been experimentally verified in U2OS osteosarcoma cells. 64 Transcriptome-wide state-of-the-art technologies such as scRNA-seq will help shape our understanding of not just aging, but also therapeutics that potentially target fundamental mechanisms of aging, such as senolytics. As noted earlier, a confounder in these analyses is the generally low expression of the canonical marker of senescence, Cdkn2a/p16 Ink4a , which is clearly detectable by RT-qPCR in the setting of aging, but poses challenges when using transcriptomewide approaches.…”