Tristetraprolin targets Nos2 expression in the colonic epithelium

Melanie A Eshelman,Gregory S Yochum,Yuka Imamura Kawasawa,Deborah J Stumpo,Rebecca M Fleeman,Stephen M Matthews,Walter A Koltun,Faoud T Ishmael,Emily M Schleicher,Perry J Blackshear

doi:10.1038/s41598-019-50957-9

Melanie A Eshelman, Gregory S Yochum + Show 8 more

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https://doi.org/10.1038/s41598-019-50957-9

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Tristetraprolin (TTP), encoded by the Zfp36 gene, is a zinc-finger protein that regulates RNA stability primarily through association with 3′ untranslated regions (3′ UTRs) of target mRNAs. While TTP is expressed abundantly in the intestines, its function in intestinal epithelial cells (IECs) is unknown. Here we used a cre-lox system to remove Zfp36 in the mouse epithelium to uncover a role for TTP in IECs and to identify target genes in these cells. While TTP was largely dispensable for establishment and maintenance of the colonic epithelium, we found an expansion of the proliferative zone and an increase in goblet cell numbers in the colon crypts of Zfp36ΔIEC mice. Furthermore, through RNA-sequencing of transcripts isolated from the colons of Zfp36fl/fl and Zfp36ΔIEC mice, we found that expression of inducible nitric oxide synthase (iNos or Nos2) was elevated in TTP-knockout IECs. We demonstrate that TTP interacts with AU-rich elements in the Nos2 3′ UTR and suppresses Nos2 expression. In comparison to control Zfp36fl/fl mice, Zfp36ΔIEC mice were less susceptible to dextran sodium sulfate (DSS)-induced acute colitis. Together, these results demonstrate that TTP in IECs targets Nos2 expression and aggravates acute colitis.

Highlights

A single layer of epithelial cells lines the intestines and forms a physical barrier to protect underlying tissue from the microbiota and noxious contents of the lumen[1]
Despite robust TTP expression in the intestine, little is known about its function in intestinal epithelial cells (IECs) and whether it contributes to intestinal homeostasis or digestive diseases[10]
Zfp[36] expression was dramatically reduced in RNAs isolated from full-thickness tissue and was reduced more than 99% in purified colonic epithelium from ΔIEC mice (Fig. 1C,D). This reduction was apparent at the protein level as very little TTP was detected by western blot analysis of ΔIEC colonic lysates (Fig. 1E)

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Introduction

A single layer of epithelial cells lines the intestines and forms a physical barrier to protect underlying tissue from the microbiota and noxious contents of the lumen[1]. RNA-binding proteins can either degrade or stabilize transcripts by associating with 3′ UTRs of target transcripts and recruiting multiprotein complexes One such protein is tristetraprolin (TTP; known as TIS11, NUP475, and G0S24), which is encoded by the Zfp[36] gene[5]. In this study we sought to identify TTP targets in IECs and to uncover the role for epithelial TTP in intestinal homeostasis and acute colitis. We identified increased Nos[2] expression in TTP-depleted IECs. we demonstrated that Nos[2] is targeted by TTP through interactions with its 3′ UTR. We demonstrated that Nos[2] is targeted by TTP through interactions with its 3′ UTR These post-transcriptional alterations in TTP-depleted IECs protect mice from a model of acute colitis

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