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Two initiation sites for foot-and-mouth disease virus polyprotein in vivo

B E Clarke, D V Sangar, J N Burroughs

    The Journal of General Virology
    |December 1, 1985
    PubMed

    Insights

    Foot-and-mouth disease virus (FMDV) RNA translation initiates at two sites, producing P20a and P16 proteins. Their N-terminal differences and surrounding sequences influence initiation site usage and in vivo/in vitro synthesis ratios.

    Area of Science:

    • Molecular Biology
    • Virology
    • Genetics

    Background:

    • Eukaryotic mRNA translation typically starts at a single site.
    • Foot-and-mouth disease virus (FMDV) presents a unique case with dual translation products from its RNA.
    • Previous research indicated two primary translation products, P20a and P16, from the FMDV genome's 5' coding region.

    Purpose of the Study:

    • To confirm the presence of two translation initiation sites for FMDV RNA.
    • To investigate the structural differences between the two primary translation products.
    • To analyze the nucleotide sequences influencing initiation site selection and protein synthesis regulation.

    Main Methods:

    • Partial protease digestion to analyze protein N-terminal differences.
    • Sequence analysis of FMDV subtypes (A10 and A12) to identify initiator AUG codons.
    • In vitro and in vivo protein synthesis assays to compare translation product ratios.

    Main Results:

    • Proteins P20a and P16 differ only at their N termini, confirming two initiation sites.
    • Sequence analysis revealed two initiator AUG codons in the expected positions for FMDV subtypes.
    • The relative usage of initiation sites correlates with surrounding nucleotide sequences.
    • In vitro and in vivo synthesis ratios of P20a and P16 differ significantly, suggesting in vivo regulation.
    • The cleavage site for the structural protein precursor P88 is located more N-terminally than previously reported.

    Conclusions:

    • FMDV RNA translation utilizes two distinct initiation sites, generating proteins with different N termini.
    • Nucleotide sequences flanking initiator codons play a crucial role in regulating translation initiation site selection.
    • A post-transcriptional or translational control mechanism likely regulates P20a synthesis in vivo.
    • The precise localization of the P88 cleavage site provides new insights into FMDV polyprotein processing.

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