mRNA degradation in Escherichia coli: a novel factor which impedes the exoribonucleolytic activity of PNPase at stem-loop structures

Authors

  • Helen Causton,

    1. Imperial Cancer Research Fund Laboratories, Institute of Molecular Medicine and Nuffield Department of Clinical Biochemistry, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK.
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    • Whitehead Institute, Nine Cambridge Center, Cambridge, Massachusetts, USA.

  • Béatrice Py,

    1. Imperial Cancer Research Fund Laboratories, Institute of Molecular Medicine and Nuffield Department of Clinical Biochemistry, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK.
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  • Robert S. McLaren,

    1. Imperial Cancer Research Fund Laboratories, Institute of Molecular Medicine and Nuffield Department of Clinical Biochemistry, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK.
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    • McArdle Laboratory for Cancer Research, University of Wisconsin, 1400 University Avenue, Madison, Wisconsin 53706, USA.

  • Christopher F. Higgins

    Corresponding author
    1. Imperial Cancer Research Fund Laboratories, Institute of Molecular Medicine and Nuffield Department of Clinical Biochemistry, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK.
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Summary

Stem-loop structures can protect upstream mRNA from degradation by impeding the processive activities of 3′–5′ exoribonucleases. The ability of such structures to impede exonuclease activity in vitro is insufficient to account for the stability they can confer on mRNA in vivo. In this study we identify a factor from Escherichia coli which specifically impedes the processive activity of the 3′–5′ exonuclease PNPase at stem-loop structures in vitro. This factor can, potentialiy, reconcile the apparent discrepancy between the ability of 3′ stem-loop structures to stabilize upstream mRNA in vitro and in vivo. Its mechanism of action, and possible role in regulating mRNA degradation, is discussed.

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