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Covalent linkage between RNA and nascent DNA in the slime mold, Physarum polycephalum

M A Waqar, J A Huberman

    Biochimica Et Biophysica Acta
    |April 2, 1975
    PubMed

    Insights

    Physarum polycephalum DNA synthesis begins with short RNA primers. These RNA-DNA junctions, containing phosphodiester bonds, are later found in longer DNA strands.

    Area of Science:

    • Molecular Biology
    • Cell Biology
    • Biochemistry

    Background:

    • DNA replication requires initiation of new DNA strands.
    • The role of RNA in initiating DNA synthesis in eukaryotic slime molds was not fully understood.

    Purpose of the Study:

    • To investigate the nature of nascent DNA chains in Physarum polycephalum.
    • To determine if RNA is involved in the initiation of DNA synthesis in this organism.

    Main Methods:

    • Injection of alpha-32P-labeled deoxyribonucleoside triphosphates into Physarum polycephalum plasmodia.
    • Analysis of incorporated nucleotides in DNA strands of varying lengths using denaturation and Cs2SO4 density gradient centrifugation.
    • Alkali hydrolysis to identify ribonucleotides.

    Main Results:

    • Newly synthesized DNA strands were initially short (<300 nucleotides).
    • A small fraction of incorporated phosphorus (32P) was transferred to ribonucleotides, indicating RNA presence.
    • RNA-DNA junctions were identified, with varying ribo- and deoxyribonucleotide combinations.

    Conclusions:

    • Short RNA sequences act as primers, covalently linked to nascent DNA chains in Physarum polycephalum.
    • These RNA primers are essential for initiating DNA synthesis in this eukaryotic slime mold.
    • The findings contribute to understanding the fundamental mechanisms of DNA replication.

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