Poly(ADP-ribosyl)ation enhances HuR oligomerization and contributes to pro-inflammatory gene mRNA stabilization

Yueshuang Ke,Istvan Boldogh,Ameer Ali Bohio,Ruoxi Wang,Jing Zhang,Xueqing Ba,Xueping Lv,Xingyue Fu,Xianlu Zeng,Wenjing Hao

doi:10.1007/s00018-020-03618-4

Abstract

Poly(ADP-ribosyl)ation (PARylation) is an important post-translational modification mainly catalyzed by poly-ADP-ribose polymerase 1 (PARP1). In addition to having important roles in DNA damage detection and repair, it functions in gene expression regulation, especially at the posttranscriptional level. Embryonic lethal abnormal vision-like 1/human antigen R (ELAVL/HuR), a canonical 3′ untranslated region AU-rich element-binding protein, is a crucial mRNA-stabilizing protein that protects target mRNAs from RNA-destabilizing protein- or microRNA-induced silencing complex (miRISC)-mediated degradation. Additionally, in some cases, HuR itself either promotes or suppresses translation. Here, we demonstrated that in response to inflammatory stimuli, the PARylation of HuR, mostly at the conserved D226 site, by PARP1 increased the formation of the HuR oligomer/multimer, and HuR oligomerization promoted the disassociation of miRISC and stabilized the pro-inflammatory gene mRNAs. The prevention of PARP1 activation or HuR oligomerization attenuated lipopolysaccharide-induced inflammatory gene expression and the airway recruitment of neutrophils in mouse lungs. The present study verified a novel mechanism of PARP1 and HuR PARylation in the RNA stability regulation, increasing our understanding of how PARP1 regulates gene expression.

Highlights

Eukaryotes employ multiple post-transcriptional mechanisms to adjust their gene expression levels in response to external stimuli and changes in cellular physiopathology
Cells were challenged with TNFα for 1 h, treated with the amine-specific chemical crosslinking reagent disuccinimidyl suberate (DSS), and the HuR contents under non-denaturing and non-reducing conditions were analyzed by western blotting using an anti-HuR antibody (Ab)
To rule out the possibility that other cell proteins cross-linked with HuR under DSS-treatment conditions and to confirm the formation of the HuR oligomer in response to inflammatory stimulation, Flagtagged HuR (Flag-HuR) was expressed in HEK293 cells, and the cell extracts were subjected to immunoprecipitation using anti-FLAG Ab

Summary

Introduction

Eukaryotes employ multiple post-transcriptional mechanisms to adjust their gene expression levels in response to external stimuli and changes in cellular physiopathology. Many proteins that regulate cell growth, differentiation and inflammation are coded by unstable mRNAs. Many proteins that regulate cell growth, differentiation and inflammation are coded by unstable mRNAs Among these mRNAs are short-lived mRNAs, which are often characterized by the presence of cis-regulatory elements that are responsible for their degradation [1]. One class of such elements is represented by the AU-rich elements (AREs), which are mainly present in 3′ untranslated regions (3′ UTRs) and bound by RNA-binding proteins (RBPs) [2, 3]. The functional regulation of HuR is achieved through protein modifications, including phosphorylation, methylation, ubiquitination, NEDDylation and proteolytic cleavage, which may regulate its subcellular localization, interactions with other proteins or associations with target RNAs [12, 17,18,19,20,21,22,23,24,25,26]

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