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Co-immunoprecipitation of the Mouse Mx1 Protein with the Influenza A Virus Nucleoprotein
Published on: April 21, 2015
Selective incorporation of vRNP into influenza A virions determined by its specific interaction with M1 protein
Chutikarn Chaimayo1, Tsuyoshi Hayashi2, Andrew Underwood2
1Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, United States; Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
Abstract:
Influenza A viruses contain eight single-stranded, negative-sense RNA segments as viral genomes in the form of viral ribonucleoproteins (vRNPs). During genome replication in the nucleus, positive-sense complementary RNPs (cRNPs) are produced as replicative intermediates, which are not incorporated into progeny virions. To analyze the mechanism of selective vRNP incorporation into progeny virions, we quantified vRNPs and cRNPs in the nuclear and cytosolic fractions of infected cells, using a strand-specific qRT-PCR. Unexpectedly, we found that cRNPs were also exported to the cytoplasm. This export was chromosome region maintenance 1 (CRM1)-independent unlike that of vRNPs. Although both vRNPs and cRNPs were present in the cytosol, viral matrix (M1) protein, a key regulator for viral assembly, preferentially bound vRNPs over cRNPs. These results indicate that influenza A viruses selectively uptake cytosolic vRNPs through a specific interaction with M1 during viral assembly.
Insights
Influenza A virus selectively packages viral ribonucleoproteins (vRNPs) for progeny, not complementary RNPs (cRNPs). This selective uptake is mediated by the matrix (M1) protein during viral assembly.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Influenza A viruses utilize eight RNA segments forming viral ribonucleoproteins (vRNPs).
- Replication produces complementary RNPs (cRNPs) as intermediates, not packaged into new viruses.
Purpose of the Study:
- To investigate the mechanism of selective vRNP incorporation into progeny virions.
- To quantify vRNPs and cRNPs in infected cell fractions.
Main Methods:
- Strand-specific quantitative reverse transcription PCR (qRT-PCR).
- Fractionation of infected cells into nuclear and cytosolic components.
Main Results:
- cRNPs are exported to the cytoplasm independently of CRM1.
- Viral matrix (M1) protein preferentially binds vRNPs over cRNPs in the cytosol.
- Selective uptake of cytosolic vRNPs by M1 during assembly.
Conclusions:
- Influenza A virus assembly involves selective recognition and packaging of vRNPs.
- M1 protein plays a crucial role in distinguishing vRNPs from cRNPs for incorporation.
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