Epigenetically regulated miR-449a enhances hepatitis B virus replication by targeting cAMP-responsive element binding protein 5 and modulating hepatocytes phenotype.

Xiaoyong Zhang,Hongyan Liu,Bo Qin,Zhanglian Xie,Jinlin Hou,Mengji Lu,Chunchen Wu,Wangyu Deng

doi:10.1038/srep25389

Abstract

Cellular microRNAs (miRNAs) are able to influence hepatitis B virus (HBV) replication directly by binding to HBV transcripts or indirectly by targeting cellular factors. Here, we investigate the effect of epigenetically regulated miR-449a on HBV replication and the underlying mechanisms. miR-449a expression was lower in human hepatocellular carcinoma (HCC) cells than in primary hepatocytes and could be induced by trichostatin A. Ectopic miR-449a expression in HCC cells strongly enhanced HBV replication, transcription, progeny virions secretion, and antigen expression in a dose-dependent manner. miR-449a directly targeted cAMP-responsive element binding protein 5 (CREB5), which in turn induced the expression of farnesoid X receptor α (FXRα), a transcription factor that facilitates HBV replication. CREB5 knockdown and overexpression demonstrated that it is a negative regulator of HBV replication. Additionally, miR-449a overexpression inhibited proliferation, caused cell cycle arrest, and promoted HCC cell differentiation. The results indicated that epigenetically regulated miR-449a targets CREB5 to increase FXRα expression, thereby promoting HBV replication and gene expression. Our findings provide a new understanding of the role of miRNAs in HBV replication.

Highlights

MiRNAs comprise a family of endogenous, conserved noncoding RNAs approximately 21–25 nucleotides in length that are involved in either translational arrest or RNA degradation via imperfect base pairing with the 3′ -untranslated region (UTR) or coding region of the target transcript[6]
We previously reported that trichostatin A (TSA), a potent HDAC inhibitor that increases histone acetylation, could enhance hepatitis B virus (HBV) replication in HBV-stably transfected HepG2.2.15 cells[17]
These results are consistent with a previous observation in cell-based replication systems and patient liver samples that HBV replication is regulated by the acetylation status of H3/H4 histones bound to the viral genome[25]

Summary

Introduction

MiRNAs comprise a family of endogenous, conserved noncoding RNAs approximately 21–25 nucleotides in length that are involved in either translational arrest or RNA degradation via imperfect base pairing with the 3′ -untranslated region (UTR) or coding region of the target transcript[6]. HDAC1-3 upregulation reduces the expression of miR-449a in HCC cell lines, whereas miR-449a overexpression reduces the expression of its target c-MET, decreases the phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2), and inhibits the proliferation of HCC cells[18]. Both the HDAC1 and ERK pathways, which are targeted by miR-449a, were previously reported to be involved in regulating HBV replication[25,26]. This study aims to examine the effect of miR-449a regulation on HBV and to explore the underlying molecular mechanisms

Objectives

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Results

Conclusion