Date Published: September 09, 2016
Publisher: John Wiley and Sons Inc.
Author(s): Hui Wang, Limin Han, Ganye Zhao, Hong Shen, Pengfeng Wang, Zhaomeng Sun, Chenzhong Xu, Yuanyuan Su, Guodong Li, Tanjun Tong, Jun Chen.
Senescent cells display a senescence‐associated secretory phenotype (SASP) which contributes to tumor suppression, aging, and cancer. However, the underlying mechanisms for SASP regulation are not fully elucidated. SIRT1, a nicotinamide adenosine dinucleotide‐dependent deacetylase, plays multiple roles in metabolism, inflammatory response, and longevity, etc. However, its posttranscriptional regulation and its roles in cellular senescence and SASP regulation are still elusive. Here, we identify the RNA‐binding protein hnRNP A1 as a posttranscriptional regulator of SIRT1, as well as cell senescence and SASP regulator. hnRNP A1 directly interacts with the 3′ untranslated region of SIRT1 mRNA, promotes its stability, and increases SIRT1 expression. hnRNP A1 delays replicative cellular senescence and prevents from Ras OIS via upregulation of SIRT1 expression to deacetylate NF‐κB, thus blunting its transcriptional activity and subsequent IL‐6/IL‐8 induction. hnRNP A1 overexpression promotes cell transformation and tumorigenesis in a SIRT1‐dependent manner. Together, our findings unveil a novel posttranscriptional regulation of SIRT1 by hnRNP A1 and uncover a critical role of hnRNP A1‐SIRT1–NF‐κB pathway in regulating cellular senescence and SASP expression.
Cellular senescence, including oncogene‐induced cellular senescence (OIS), is a stable cell cycle arrest which limits the proliferation of damaged cells and acts as a natural barrier against tumor development in vivo (Collado & Serrano, 2010). One distinct feature of senescent cells compared with young cells is that senescent cells secret a wide range of cytokines, chemokines, and other proteins termed as senescence‐associated secretory phenotype (SASP). SASP plays multiple biological functions such as tumor suppression, tissue repair, and embryonic development, by either autocrine or paracrine fashion. However, with senescent cell accumulation in late life, SASP can promote tumor formation and invasion and may contribute to aging and many age‐related diseases (van Deursen, 2014; Salama et al., 2014). Many SASP factors including key components IL‐6 and IL‐8 are mainly regulated at transcriptional level by transcription factor NF‐κB (Acosta et al., 2008; Kuilman et al., 2008). Despite various signaling pathways participate in regulating SASP production by altering NF‐κB pathway components phosphorylation status and activities (Wang et al., 2014; Kang et al., 2015), little is known about whether NF‐κB itself and its activity are subjected to other posttranslational modifications and regulations during senescence. Previous report shows that acetylation of lysine 310 in p65/RelA is required for the full transcriptional activity of NF‐κB (Chen et al., 2002). However, whether the acetylation status of NF‐κB is altered during senescence, whether NF‐κB acetylation has effect on the SASP expression, and how NF‐κB acetylation is regulated during senescence remain largely unknown.
SIRT1 plays multiple roles including CR, stress resistance, metabolism, and against age‐related diseases which tightly associated with healthy aging (Houtkooper et al., 2012; Giblin et al., 2014). However, how is SIRT1 itself regulated in aging, especially its posttranscriptional regulation is barely understood. Here, we identified that hnRNP A1 as a RNA‐binding protein directly bonds to SIRT1 mRNA 3′UTR and stabilizes SIRT1 mRNA and thus augments SIRT1 at both mRNA and protein levels (Figs 1 and 2). Therefore, our study shed new light on the posttranscriptional regulation of SIRT1 by hnRNP A1.
Antibodies, reagents, and cell lines used in this study are described in Supplemental Experimental Procedures. All of experiments were processed according to the standard protocols. Plasmids, viral infection, real‐time PCR, ChIP, immunoblot analysis, RNP‐IP, biotinylated RNA pull‐down assay, luciferase reporter gene assays, RNA isolation, RNA half‐life determination, SA‐β‐gal staining, cell cycle analysis, ELISA, soft agar, tumorigenic assay, etc., are provided in detail in Supplemental Experimental Procedures.
This work was supported by National Key Basic Research Program of China Grants 2013CB530801 and 2012CB911203.
All the authors declare no conflict of interest.
HW and JC designed research; HW, LMH, GYZ, HS, PFW, ZMS, CZX, YYS, and GDL performed research and analyzed the data; TJT supervised the research; and HW and JC wrote the manuscript.