A complex genome-microRNA interplay in human mitochondria.

Santosh Shinde,Utpal Bhadra

doi:10.1155/2015/206382

Abstract

Small noncoding regulatory RNA exist in wide spectrum of organisms ranging from prokaryote bacteria to humans. In human, a systematic search for noncoding RNA is mainly limited to the nuclear and cytosolic compartments. To investigate whether endogenous small regulatory RNA are present in cell organelles, human mitochondrial genome was also explored for prediction of precursor microRNA (pre-miRNA) and mature miRNA (miRNA) sequences. Six novel miRNA were predicted from the organelle genome by bioinformatics analysis. The structures are conserved in other five mammals including chimp, orangutan, mouse, rat, and rhesus genome. Experimentally, six human miRNA are well accumulated or deposited in human mitochondria. Three of them are expressed less prominently in Northern analysis. To ascertain their presence in human skeletal muscles, total RNA was extracted from enriched mitochondria by an immunomagnetic method. The expression of six novel pre-miRNA and miRNA was confirmed by Northern blot analysis; however, low level of remaining miRNA was found by sensitive Northern analysis. Their presence is further confirmed by real time RT-PCR. The six miRNA find their multiple targets throughout the human genome in three different types of software. The luciferase assay was used to confirm that MT-RNR2 gene was the potential target of hsa-miR-mit3 and hsa-miR-mit4.

Highlights

Mitochondria are known as the powerhouse of the cell; they are membrane bound organelles present in most eukaryotic cells
Luciferase assay was used to invent whether MT-RNR2 was the direct target of hsa-miR-mit3 or hsa-miR-mit4 microRNA separately
A wild type and a mutated 3󸀠 UTR of MT-RNR2 gene were subcloned into the psiCHECK-2 luciferase miRNA expression reporter vector as described earlier [23]

Summary

Introduction

Mitochondria are known as the powerhouse of the cell; they are membrane bound organelles present in most eukaryotic cells. The numbers of mitochondria are generally varied from cell to cell and organism to organism. Mitochondria have their own genome (mitochondrial DNA, mtDNA) that is different from nuclear genome. Human mitochondrial genome carries 37 genes in a 16.5 kb small circular genome. Of these 13 specific protein products especially the subunit of the respiratory gene complex and the remaining 24 encode RNA products. Mitochondria genome imported 22 tRNA and is involved in the trafficking of different proteins through distinct molecular mechanisms [1]

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Conclusion