Abstract

Transmissible gastroenteritis virus (TGEV), belonging to the coronaviridae family, is the key cause of the fatal diarrhea of piglets and results in many pathological processes. microRNAs (miRNAs) play a key role in the regulation of virus-induced apoptosis. During the process of apoptosis induced by TGEV infection in PK-15 cells, the miR-27b is notably down-regulated. Thus, we speculate that miR-27b is involved in regulating the process of apoptosis in PK-15 cells. In this study we demonstrated that the over-expression of miR-27b led to the inhibition of TGEV-induced apoptosis, reduction of Bax protein level, and decrease of caspase-3 and −9 activities. Conversely, silencing of miR-27b by miR-27b inhibitors enhanced apoptosis via up-regulating Bax expression and promoting the activities of caspase-3 and −9 in TGEV-infected cells. Subsequently, the runt-related transcription factor 1 (RUNX1) is a candidate target of miR-27b predicted by bioinformatics search. We further identified that the miR-27b directly bound to the 3′ UTR of RUNX1 mRNA and suppressed RUNX1 expression, which indicates RUNX1 is the direct target gene of miR-27b. The over-expression of RUNX1 increased apoptosis and knockdown RUNX1blocked apoptosis of viral-infected cells via regulating Bax expression and the activities of caspase-3 and −9. Our data reveal that miR-27b may repress the mitochondrial pathway of apoptosis by targeting RUNX1, indicating that TGEV may induce apoptosis via down-regulating miR-27b and that miR-27b may act as a target for therapeutic intervention.

Highlights

  • transmissible gastroenteritis virus (TGEV), a member of Coronaviridae family, is an enveloped virus with a positive-sense single-stranded RNA genome (Weiss & Leibowitz, 2011)

  • The results showed that the over-expression of miR-27b led to a decrease of apoptotic rate and the down-expression of miR-27b increased apoptotic rate at 24 and 48 hpi (Fig. 1A), indicating that miR-27b attenuated apoptosis induced by TGEV infection in PK-15 cells

  • We previously found that TGEV infection could cause PK-15 cell apoptosis through mitochondria-mediated pathway and FasL-mediated apoptotic pathway

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Summary

Introduction

TGEV, a member of Coronaviridae family, is an enveloped virus with a positive-sense single-stranded RNA genome (Weiss & Leibowitz, 2011). Apoptosis is a process of self-destruction in response to a variety of stimuli such as viral infection. Infection of coronavirus such as porcine epidemic diarrhea virus (PEDV). How to cite this article Zhao et al (2016), miR-27b attenuates apoptosis induced by transmissible gastroenteritis virus (TGEV) infection via targeting runt-related transcription factor 1 (RUNX1). (Kim & Lee, 2014), infectious bronchitis virus (IBV) (Li, Tam & Liu, 2007), severe acute respiratory syndrome coronavirus (SARS-CoV) (Krahling et al, 2009), may result in host cell apoptosis. We have reported that TGEV infection induced apoptosis via mitochondria mediated apoptotic pathway in PK-15 cells (Ding et al, 2012; Ding et al, 2013)

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