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MicroRNAs (miRNA) are non-coding RNA around 22 nucleotides in length.  They are responsible for gene expression and preventing translation of mRNA. miRNAs are highly conserved in evolutionary terms [1].

Precursors to miRNA are made by RNA Polymerase II. These precursors are then processed and incorporated into a set of proteins to create an RNA-Induced Silencing Complex [2].

miRNA are capable of regulating many RNA and in combination with each other.

One of the first families of miRNA, Let-7, was discovered in Caenorhabditis elegans. Let-7 has since been discovered in humans and is controlled at post-transcriptional level. Misregulation of Let-7 can lead to uncontrolled cell growth and cancer [3].


  1. S.Roush & F.J. Slack (2008), Trends in Cell Biology, 18(10), 505-516
  2. Alberts et al., Molecular Biology of the Cell, 5th edition, page 494.
  3. S. Roush & F.J. Slack, (2008), Trends in Cell Biology, 18(10), 505-516
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