Biology Reference
In-Depth Information
Chapter 1
The Pathway of miRNA Maturation
Michael Sand
Abstract
MicroRNAs (miRNAs) are a novel class of 17-23 nucleotide short, nonprotein-coding RNA molecules
which have emerged to be key players in posttranscriptional gene regulation. In this chapter we give an
in-depth review of the classic, canonical mammalian miRNA maturation pathway and discuss new, nonca-
nonical alternatives such as the mirtron pathway which were recently described.
Key words
MicroRNA, Primary-microRNA, Drosha, Precursor-microRNA, Dicer, Mirtron
1
Introduction: The Classic miRNA Maturation Pathway
MicroRNAs (miRNAs) are 17-23 nt short, nonprotein-coding
RNA (ncRNA) molecules which are highly conserved through the
genome of viruses, plants, animals, and humans. Accumulating evi-
dence suggests their fundamental role in the concept of posttran-
scriptional gene regulation as they have shown to play an important
role during development, cellular physiology, and disease pathol-
ogy. Recently this group of ncRNAs has received considerable
attention in biomedical research because of their pervasive level of
gene regulation.
In this chapter we focus on the classic, canonical mammalian
miRNA maturation pathway (Fig.
1
) which shows a stepwise matu-
ration pattern located inside the nucleus and in the cytoplasm and
discuss new, alternative miRNA pathways recently described.
2
Intranuclear Maturation: The Primary-miRNA Transcript and Drosha Cleavage
In eukaryotes the genetic information which is necessary for the
maturation of miRNAs is encoded throughout the whole genome
which is stored on chromosomes inside the nucleus. In humans
only approximately 1.5 % of the three billion base pairs of DNA are
