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Related Concept Videos

MicroRNAs01:22

MicroRNAs

MicroRNA (miRNA) are short, regulatory RNA transcribed from introns—non-coding regions of a gene—or intergenic regions—stretches of DNA present between genes. Several processing steps are required to form biologically active, mature miRNA. The initial transcript, called primary miRNA (pri-mRNA), base-pairs with itself forming a stem-loop structure. Within the nucleus, an endonuclease enzyme, called Drosha, shortens the stem-loop structure into hairpin-shaped pre-miRNA. After the pre-miRNA ends...
RNA Interference01:23

RNA Interference

RNA interference (RNAi) is a process in which a small non-coding RNA molecule blocks the post-transcriptional expression of a gene by binding to its messenger RNA (mRNA) and preventing the protein from being translated.
This process occurs naturally in cells, often through the activity of genomically-encoded microRNAs. Researchers can take advantage of this mechanism by introducing synthetic RNAs to deactivate specific genes for research or therapeutic purposes. For example, RNAi could be used...
pre-mRNA Processing02:01

pre-mRNA Processing

In eukaryotic cells, transcripts made by RNA polymerase are modified and processed before exiting the nucleus. Unprocessed RNA is called precursor mRNA or pre-mRNA to distinguish it from mature mRNA.
Once about 20-40 ribonucleotides have been joined together by RNA polymerase, a group of enzymes adds a “cap” to the 5’ end of the growing transcript. In this process, a 5’ phosphate is replaced by modified guanosine that has a methyl group attached to it (7-Methyl guanosine). This 5’ cap helps the...
RNA Interference01:23

RNA Interference

RNA interference (RNAi) is a process in which a small non-coding RNA molecule blocks the post-transcriptional expression of a gene by binding to its messenger RNA (mRNA) and preventing the protein from being translated.
This process occurs naturally in cells, often through the activity of genomically-encoded microRNAs. Researchers can take advantage of this mechanism by introducing synthetic RNAs to deactivate specific genes for research or therapeutic purposes. For example, RNAi could be used...
MicroRNAs01:22

MicroRNAs

MicroRNA (miRNA) are short, regulatory RNA transcribed from introns—non-coding regions of a gene—or intergenic regions—stretches of DNA present between genes. Several processing steps are required to form biologically active, mature miRNA. The initial transcript, called primary miRNA (pri-mRNA), base-pairs with itself forming a stem-loop structure. Within the nucleus, an endonuclease enzyme, called Drosha, shortens the stem-loop structure into hairpin-shaped pre-miRNA. After the pre-miRNA ends...
MicroRNAs01:22

MicroRNAs

MicroRNA (miRNA) are short, regulatory RNA transcribed from introns (non-coding regions of a gene) or intergenic regions (stretches of DNA present between genes). Several processing steps are required to form biologically active, mature miRNA. The initial transcript, called primary miRNA (pri-mRNA), base-pairs with itself, forming a stem-loop structure. Within the nucleus, an endonuclease enzyme, called Drosha, shortens the stem-loop structure into hairpin-shaped pre-miRNA. After the pre-miRNA...

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A Bioinformatics Pipeline to Accurately and Efficiently Analyze the MicroRNA Transcriptomes in Plants
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Intronic microRNA precursors that bypass Drosha processing.

J Graham Ruby1, Calvin H Jan, David P Bartel

  • 1Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, Massachusetts 02142, USA.

Nature
|June 26, 2007
PubMed
Summary

Scientists discovered a new microRNA (miRNA) pathway using debranched introns called mirtrons. These bypass Drosha processing, offering an alternative route for miRNA biogenesis in animals.

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Area of Science:

  • Molecular Biology
  • Genetics
  • RNA Biology

Background:

  • MicroRNAs (miRNAs) are small endogenous RNAs regulating gene expression by repressing messenger RNAs.
  • Canonical miRNA biogenesis involves Drosha and Dicer processing of pre-miRNA hairpins.
  • The precise mechanisms and evolutionary origins of miRNA biogenesis pathways are areas of active research.

Purpose of the Study:

  • To identify alternative pathways for microRNA biogenesis.
  • To investigate the role of introns in miRNA production.
  • To explore the evolutionary origins of microRNAs.

Main Methods:

  • Bioinformatic analysis to identify potential miRNA precursors.
  • Comparative genomics to assess evolutionary conservation.
  • Functional characterization of identified mirtrons.

Main Results:

  • Discovery of 'mirtrons,' debranched introns mimicking pre-miRNAs.
  • Identification of 14 mirtrons in Drosophila melanogaster and 4 in Caenorhabditis elegans.
  • Evidence of evolutionary conservation suggesting regulatory roles for mirtrons.

Conclusions:

  • A novel miRNA biogenesis pathway exists, utilizing debranched introns (mirtrons).
  • Mirtrons bypass the canonical Drosha-dependent processing step.
  • This pathway may represent an ancient mechanism for miRNA evolution predating Drosha.