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Updated: Jul 15, 2026

Sequence-specific Labeling of Nucleic Acids and Proteins with Methyltransferases and Cofactor Analogues
12:07

Sequence-specific Labeling of Nucleic Acids and Proteins with Methyltransferases and Cofactor Analogues

Published on: November 22, 2014

Methyl labeling of HeLa cell hnRNA: a comparison with mRNA

M Salditt-Georgieff, W Jelinek, J E Darnell

    Cell
    |February 1, 1976
    PubMed

    Insights

    HeLa cell messenger RNA (mRNA) and heterogeneous nuclear RNA (hnRNA) contain methylation. hnRNA methylation and cleavage may generate mRNA, with some mRNA potentially derived from hnRNA 5' regions.

    Area of Science:

    • Molecular Biology
    • RNA Biochemistry
    • Cellular Biology

    Background:

    • HeLa cell mRNA typically possesses 1-2 N6-methyladenosine (m6Ap) residues and a methylated 5' cap structure.
    • Heterogeneous nuclear RNA (hnRNA) is longer than mRNA and contains both m6Ap and cap structures, with a higher m6Ap content.

    Purpose of the Study:

    • To investigate the methylation patterns and potential relationship between hnRNA and mRNA in HeLa cells.
    • To explore the processing of hnRNA into mRNA, focusing on methylation and cleavage events.

    Main Methods:

    • Analysis of mRNA and hnRNA molecules in HeLa cells.
    • Characterization of methylated residues (m6Ap) and 5' cap structures.
    • Identification of T2 RNAase-resistant, methyl-labeled oligonucleotides in nuclear RNA.

    Main Results:

    • hnRNA contains significantly more m6Ap residues (4-6 times) than mRNA.
    • Nuclear RNA exhibits T2 RNAase-resistant, methyl-labeled dinucleotides and trinucleotides, absent in mRNA.
    • These dinucleotides may serve as precursors for 2'-O-methylated nucleotides found in mRNA cap structures.

    Conclusions:

    • Internal methylation of hnRNA (m6Ap and 2'-O-methyl) followed by cleavage and cap addition likely generates some HeLa cell mRNA.
    • The presence of cap structures in longer hnRNA molecules suggests that some mRNA may originate from the 5' regions of hnRNA.

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