Canonical and alternate functions of the microRNA biogenesis machinery

  1. Dan R. Littman1,5,6
  1. 1Molecular Pathogenesis Program, Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, New York 10016, USA;
  2. 2The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia;
  3. 3Structural Biology Program of the Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, New York 10016, USA;
  4. 4Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA;
  5. 5Howard Hughes Medical Institute, New York University School of Medicine, New York, New York 10016, USA

    Abstract

    The canonical microRNA (miRNA) biogenesis pathway requires two RNaseIII enzymes: Drosha and Dicer. To understand their functions in mammals in vivo, we engineered mice with germline or tissue-specific inactivation of the genes encoding these two proteins. Changes in proteomic and transcriptional profiles that were shared in Dicer- and Drosha-deficient mice confirmed the requirement for both enzymes in canonical miRNA biogenesis. However, deficiency in Drosha or Dicer did not always result in identical phenotypes, suggesting additional functions. We found that, in early-stage thymocytes, Drosha recognizes and directly cleaves many protein-coding messenger RNAs (mRNAs) with secondary stem–loop structures. In addition, we identified a subset of miRNAs generated by a Dicer-dependent but Drosha-independent mechanism. These were distinct from previously described mirtrons. Thus, in mammalian cells, Dicer is required for the biogenesis of multiple classes of miRNAs. Together, these findings extend the range of function of RNaseIII enzymes beyond canonical miRNA biogenesis, and help explain the nonoverlapping phenotypes caused by Drosha and Dicer deficiency.

    Keywords

    Footnotes

    • Received May 28, 2010.
    • Accepted July 21, 2010.
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