Related Experiment Video
Updated: Jul 8, 2026

13:48
Reverse Genetics Mediated Recovery of Infectious Murine Norovirus
Published on: June 24, 2012
Transcripts encoding the nanovirus master replication initiator proteins are terminally redundant
Ioana Grigoras1, Tatiana Timchenko1, Bruno Gronenborn1
1Institut des Sciences du Végétal, CNRS, 91198 Gif sur Yvette, France.
The Journal of General Virology
|January 17, 2008
Summary
Plant nanoviruses possess unique master replication initiator (Rep) proteins. Their mRNAs are terminally redundant, with the replication origin transcribed into RNA, potentially regulating essential Rep protein expression.
Area of Science:
- Plant Virology
- Molecular Biology
- Genomics
Background:
- Plant nanoviruses are multicomponent single-stranded DNA viruses.
- These viruses encode unique master replication initiator (Rep) proteins essential for their life cycle.
Purpose of the Study:
- To investigate the transcriptional characteristics of nanovirus genome components.
- To determine if the unique features of master Rep mRNA transcription are conserved across different nanoviruses.
Main Methods:
- Mapping the 5' and 3' termini of polyadenylated mRNAs from FBNYV and subterranean clover stunt virus.
- Analyzing the secondary structure of transcribed RNA originating from the viral DNA replication origin.
Main Results:
- Nanovirus master Rep mRNAs exhibit terminal redundancy of up to 160 nucleotides.
- The viral DNA replication origin is transcribed into RNA capable of forming extended secondary structures.
- Other nanovirus genome components, like those encoding Clink or para-Rep proteins, lack these unique transcriptional features.
Conclusions:
- Terminally redundant mRNAs and transcribed replication origins are specific to nanovirus master Rep DNAs.
- This unique transcription mechanism may serve to regulate the expression of the essential master Rep protein.
Related Concept Videos
Viruses 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...
Leaky Scanning
During most eukaryotic translation processes, the small 40S ribosome subunit scans an mRNA from its 5' end until it encounters the first start AUG codon. The large 60S ribosomal subunit then joins the smaller one to initiate protein synthesis. The location of the translation initiation is largely determined by the nucleotides near the start codon as there may be multiple translation initiation sites present on the mRNA. Marilyn Kozak discovered that the sequence RCCAUGG (where R stands for...
Retrovirus 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...
Viral Mutations
A mutation is a change in the sequence of bases of DNA or RNA in a genome. Some mutations occur during replication of the genome due to errors made by the polymerase enzymes that replicate DNA or RNA. Unlike DNA polymerase, RNA polymerase is prone to errors because it is not capable of “proofreading” its work. Viruses with RNA-based genomes, like HIV, therefore accrue mutations faster than viruses with DNA-based genomes. Because mutation and recombination provide the raw material for adaptive...
Retroviruses
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’...
Nonsense-mediated mRNA Decay
The Upf proteins that carry out nonsense-mediated decay (NMD) are found in all eukaryotic organisms, including humans. Each protein has an individual role, but they need to work in collaboration. Upf1 is an ATP-dependent RNA helicase that unwinds the RNA helix. Because Upf1 can unwind any RNA, Upf2 and Upf3 are required to help Upf1 discriminate between nonsense and normal mRNAs.
Usually, Upf3 binds to an Exon Junction Complex (EJC) at mRNA splice sites. If a ribosome fully translates the mRNA,...
Usually, Upf3 binds to an Exon Junction Complex (EJC) at mRNA splice sites. If a ribosome fully translates the mRNA,...

