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MicroRNAs

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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...

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Related Experiment Video

Updated: Jul 15, 2026

Polysome Fractionation and Analysis of Mammalian Translatomes on a Genome-wide Scale

Polysome Fractionation and Analysis of Mammalian Translatomes on a Genome-wide Scale

Published on: May 17, 2014

MicroRNAs, mRNAs, and translation.

P A Maroney¹, Y Yu, T W Nilsen

¹Center for RNA Molecular Biology and Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-4973, USA.

Cold Spring Harbor Symposia on Quantitative Biology

|March 27, 2007

Summary

MicroRNAs (miRNAs) are regulatory molecules impacting gene expression. This study found most miRNAs associate with translating mRNAs in polysomes, suggesting a role in translation regulation.

Area of Science:

Molecular Biology
Gene Regulation
Cell Biology

Background:

MicroRNAs (miRNAs) are key regulators of gene expression in animal cells, primarily by repressing protein production from target messenger RNAs (mRNAs).
Despite their widespread influence, the precise mechanisms underlying miRNA function remain incompletely understood.
Investigating the subcellular localization of miRNAs is crucial for elucidating their mode of action.

Purpose of the Study:

To investigate the subcellular distribution of microRNAs (miRNAs) in actively growing HeLa cells.
To determine the association of miRNAs with actively translating messenger RNAs (mRNAs).
To explore the impact of miRNA association on mRNA translation, specifically focusing on KRAS mRNA.

Main Methods:

Analysis of subcellular localization of miRNAs in HeLa cells.

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Identification of miRNA association with polysomal fractions containing actively translating mRNAs.

Examination of KRAS mRNA association with polysomes and its translational status.

Main Results:

The vast majority of analyzed miRNAs were found to be associated with actively translating mRNAs within polysomes.
A specific miRNA-regulated mRNA, KRAS, was also found to be polysome-associated.
Translation of the KRAS mRNA appeared to be impaired, potentially at the elongation stage, in the presence of miRNA regulation.

Conclusions:

MicroRNA (miRNA) localization within polysomes suggests a direct role in regulating the translation of associated messenger RNAs (mRNAs).
The observed impairment of KRAS mRNA translation indicates that miRNAs may influence translation elongation.
These findings contribute to a deeper understanding of the mechanistic basis of miRNA-mediated gene regulation.