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ATP/Mg++-dependent cross-linking of cap binding proteins to the 5' end of eukaryotic mRNA

N Sonenberg

    Nucleic Acids Research
    |April 10, 1981
    PubMed

    Insights

    Two proteins specifically bind to the 5' cap end of reovirus mRNA. This ATP/Mg++ dependent process differs from previously identified cap binding proteins, suggesting a new role in mRNA recognition.

    Area of Science:

    • Molecular Biology
    • Biochemistry
    • Virology

    Background:

    • The 5' cap structure of eukaryotic messenger RNA (mRNA) is crucial for its recognition by the translation machinery.
    • Previously, a 24,000-dalton (24K) cap binding protein was identified and characterized.
    • The precise mechanisms and protein factors involved in 5' cap recognition and subsequent mRNA processing are areas of ongoing research.

    Purpose of the Study:

    • To identify and characterize proteins that specifically interact with the 5' cap end of oxidized reovirus mRNA.
    • To investigate the biochemical requirements for the cross-linking of these proteins to the mRNA cap.
    • To propose a functional model for these newly identified proteins in eukaryotic mRNA metabolism.

    Main Methods:

    • UV-induced protein-nucleic acid cross-linking assays using oxidized reovirus mRNA.
    • Analysis of protein molecular weights using SDS-PAGE.
    • Biochemical characterization of cross-linking reaction conditions, including dependence on ATP, Mg++, and other nucleotides/cations.

    Main Results:

    • Two proteins, with apparent molecular weights of 28,000 (28K) and 50,000 (50K) daltons, were shown to specifically recognize and cross-link to the 5' cap of oxidized reovirus mRNA.
    • The cross-linking of these 28K and 50K proteins was dependent on Adenosine Triphosphate (ATP) and Magnesium ions (Mg++).
    • This ATP/Mg++ dependence contrasted with the previously characterized 24K cap binding protein, and non-hydrolyzable ATP analogs or other nucleotides did not substitute for ATP.

    Conclusions:

    • The 28K and 50K dalton proteins represent novel factors involved in 5' cap recognition of eukaryotic mRNAs.
    • Their ATP/Mg++ dependent cross-linking suggests a distinct mechanism compared to known cap binding proteins.
    • A model is proposed where these proteins may function in the recognition and unwinding of the 5' cap structure, potentially playing a role in mRNA processing or translation initiation.

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