Loss of HuR leads to senescence-like cytokine induction in rodent fibroblasts by activating NF-κB.

ABSTRACT

BACKGROUND: HuR (human antigen R) is a ubiquitously expressed member of the Hu/ELAV family of proteins that is involved in diverse biological processes. HuR has also been shown to play an important role in cell cycle arrest during replicative senescence in both human and mouse cells. Senescent cells not only halt their proliferation, but also activate the secretion of proinflammatory cytokines. A persistent DNA damage response is essential for the senescence-associated secretory phenotype (SASP), and increasing evidence has suggested that the SASP is associated with malignancy. METHODS: Senescence-associated phenotypes were analyzed in MEFs and other cell line in which HuR expression is inhibited by sh-RNA-mediated knockdown. RESULTS: RNAi-mediated HuR inhibition resulted in an increase in SASP-related cytokines. The induction of SASP factors did not depend on ARF-p53 pathway-mediated cell cycle arrest, but required NF-κB activity. In the absence of HuR, cells were defective in the DNA-damage response, and single strand DNA breaks accumulated, which may have caused the activation of NF-κB and subsequent cytokine induction. CONCLUSIONS: In the absence of HuR, cells exhibit multiple senescence-associated phenotypes. Our findings suggest that HuR regulates not only the replicative lifespan, but also the expression of SASP-related cytokines in mouse fibroblasts. GENERAL SIGNIFICANCE: RNA-binding protein HuR protects cells from undergoing senescence. Senescence-associated phenotypes are accelerated in HuR-deficient cells.