Related Experiment Video
Updated: Jul 3, 2026
06:03
Use of Viral Entry Assays and Molecular Docking Analysis for the Identification of Antiviral Candidates against Coxsackievirus A16
Published on: July 15, 2019
Functional analysis of structural motifs in dicistroviruses
Nobuhiko Nakashima1, Toshio Uchiumi
1National Institute of Agrobiological Sciences, Owashi 1-2, Tsukuba, Ibaraki 305-8634, Japan. nakaji@affrc.go.jp
Virus Research
|July 16, 2008
Summary
Dicistroviridae viruses possess unique RNA structures, including two distinct ORFs and an intergenic region internal ribosome entry site (IGR-IRES), facilitating distinct protein synthesis pathways compared to picornaviruses.
Area of Science:
- Virology
- Molecular Biology
- Genomics
Background:
- Dicistroviridae are positive-stranded RNA viruses with monopartite genomes.
- They share features with picornaviruses, such as genome-linked virus proteins (VPg) and poly (A) tails.
- Unlike picornaviruses' single ORF, dicistroviruses have two nonoverlapping ORFs.
Purpose of the Study:
- To describe the distinct characteristics of Dicistroviridae.
- To elucidate the role of RNA elements and viral proteins in dicistrovirus replication.
- To highlight the unique translation mechanism mediated by the IGR-IRES.
Main Methods:
- Comparative genomic analysis of Dicistroviridae and related viruses.
- Bioinformatic analysis of RNA elements, including untranslated regions (UTRs) and intergenic regions (IGRs).
- Examination of viral protein functions and their roles in replication.
Main Results:
- Dicistroviruses possess two nonoverlapping ORFs: the 5'-proximal ORF for replicases and the 3'-proximal ORF for capsid proteins.
- An internal ribosome entry site (IRES) in the 5' UTR initiates translation of the replicase polyprotein.
- A second IRES in the intergenic region (IGR-IRES) controls translation of capsid proteins, featuring a complex stem-loop structure with pseudoknots.
Conclusions:
- Dicistroviruses employ a unique two-ORF genome organization and IRES-mediated translation strategy.
- The IGR-IRES is crucial for efficient synthesis of capsid proteins, distinguishing them from viruses relying on subgenomic RNA.
- Understanding these viral RNA elements and proteins provides insights into viral replication and evolution.
Related Concept Videos
00:56Viral Structure
Viruses are extraordinarily diverse in shape and size, but they all have several structural features in common. All viruses have a core that contains a DNA- or RNA-based genome. The core is surrounded by a protective coat of proteins called the capsid. The capsid is composed of subunits called capsomeres. The capsid and genome-containing core are together known as the nucleocapsid.
01:26Size and Structure of Viral Genomes
Viral genomes exhibit remarkable diversity in size, structure, and composition, influencing their replication strategies and interactions with host cells. These genomes consist of either DNA or RNA and may be linear or circular. Additionally, they can be single-stranded or double-stranded, with each configuration affecting how the virus propagates within a host. RNA viruses, for instance, generally have smaller genomes than DNA viruses, a factor that contributes to their high mutation rates and...
02:33Retroviruses
Retroviruses and retrotransposons both insert copies of their genetic elements into the genome of the host cell. Thus, the viral genes are passed on when the host genome is replicated or translated. A typical retroviral DNA sequence contains 3-4 genes that encode the different proteins required for its structural assembly and function as a molecular parasite. This DNA is transcribed into a single mRNA, which is very similar in structure to conventional mRNAs, i.e., it is capped at the 5’...
01:29Viruses with RNA Genomes
RNA viruses are categorized into positive-strand, negative-strand, or double-stranded groups based on their genomic structure and replication mechanisms. This classification dictates how they exploit host cellular machinery for protein synthesis and replication. Some RNA viruses also utilize reverse transcription as part of their life cycle, further diversifying their replication strategies.Positive-Strand RNA VirusesPositive-strand RNA viruses have genomes that function directly as messenger...
01:19Inhibitors of Virion Maturation and Assembly
As part of their replication cycle, certain viruses synthesize long precursor proteins called polyproteins within infected host cells. In human immunodeficiency virus (HIV), two major polyproteins are produced: Gag and Gag-Pol. The Gag polyprotein supplies the structural components of the virus, while Gag-Pol includes essential viral enzymes such as reverse transcriptase, integrase, and protease. After synthesis, these polyproteins move to the host cell membrane, where they assemble into an...
01:10Retrovirus Life Cycles
Retroviruses have a single-stranded RNA genome that undergoes a special form of replication. Once the retrovirus has entered the host cell, an enzyme called reverse transcriptase synthesizes double-stranded DNA from the retroviral RNA genome. This DNA copy of the genome is then integrated into the host’s genome inside the nucleus via an enzyme called integrase. Consequently, the retroviral genome is transcribed into RNA whenever the host’s genome is transcribed, allowing the retrovirus to...