Identification of functional cis-acting RNA elements in the hepatitis E virus genome required for viral replication

PLoS Pathog. 2020 May 20;16(5):e1008488. doi: 10.1371/journal.ppat.1008488. eCollection 2020 May.

Abstract

There are approximately 20 million events of hepatitis E virus (HEV) infection worldwide annually. The genome of HEV is a single-strand, positive-sense RNA containing 5' and 3' untranslated regions and three open reading frames (ORF). HEV genome has 5' cap and 3' poly(A) tail to mimic host mRNA to escape the host innate immune surveillance and utilize host translational machineries for viral protein translation. The replication mechanism of HEV is poorly understood, especially how the viral polymerase distinguishes viral RNA from host mRNA to synthesize new viral genomes. We hypothesize that the HEV genome contains cis-acting elements that can be recognized by the virally encoded polymerase as "self" for replication. To identify functional cis-acting elements systematically across the HEV genome, we utilized an ORF1 transcomplementation system. Ultimately, we found two highly conserved cis-acting RNA elements within the ORF1 and ORF2 coding regions that are required for viral genome replication in a diverse panel of HEV genotypes. Synonymous mutations in the cis-acting RNA elements, not altering the ORF1 and ORF2 protein sequences, significantly impaired production of infectious viral particles. Mechanistic studies revealed that the cis-acting elements form secondary structures needed to interact with the HEV ORF1 protein to promote HEV replication. Thus, these cis-acting elements function as a scaffold, providing a specific "signal" that recruits viral and host factors to assemble the viral replication complex. Altogether, this work not only facilitates our understanding of the HEV life cycle and provides novel, RNA-directed targets for potential HEV treatments, but also sheds light on the development of HEV as a therapeutic delivery vector.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Genome, Viral*
  • HEK293 Cells
  • Hepatitis E virus / physiology*
  • Humans
  • Mice
  • Mice, Inbred BALB C
  • Mutation
  • Open Reading Frames / physiology
  • RNA, Viral* / biosynthesis
  • RNA, Viral* / genetics
  • Regulatory Sequences, Ribonucleic Acid / physiology*
  • Virus Replication / physiology*

Substances

  • RNA, Viral
  • Regulatory Sequences, Ribonucleic Acid

Grants and funding

The work was supported by Tsinghua-Peking University Center of Life Sciences (045-61020100119), Tsinghua University Initiative Scientific Research Program (2019Z06QCX10), Beijing Advanced Innovation Center for Structure Biology (100300001) and Start-up Foundation of Tsinghua University (53332101319). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.