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Human mitochondria hub of small RNAs: Analysis by deep Sequencing

ABSTRACT: We report here that human mitochondria contain small RNA including microRNA, piRNA, tRNA, rRNA, and RNA repeats. Mitochondria from human cells were purified and RNA isolated. Small RNAs were purified, library generated and analyzed by Illumina Hiseq 2000 system. The sequencing generated 19.5 and 17.7 million reads from HEK-293 and HeLa respectively. 91% and 97% sequences of HEK293 and HeLa respectively were annotated to various classes of small RNA. The total percentage of 4.21 and 2.58 sequences from HEK293 and HeLa respectively was found to be of miRNA. Further, we found only 1.2 % sequences from both the libraries aligned to mitochondrial genome. These results suggest that there is efficient transport of nuclear encoded small RNA to mitochondria. The small RNA in mitochondria may regulate critical cellular processes.

ORGANISM(S): Homo sapiens

PROVIDER: GSE32185 | GEO | 2013/03/05

SECONDARY ACCESSION(S): PRJNA147397

REPOSITORIES: GEO

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Project description:MicroRNAs (miRNAs) are small non-coding RNAs that associate with Argonaute 2 protein to regulate gene expression at the post-transcriptional level in the cytoplasm. However, recent studies have reported that some miRNAs localize to and function in other cellular compartments. Mitochondria harbour their own genetic system that may be a potential site for miRNA-mediated post-transcriptional regulation. We aimed at investigating whether nuclear-encoded miRNAs can localize to and function in human mitochondria. To enable identification of mitochondrial-enriched miRNAs, we profiled the mitochondrial and cytosolic RNA fractions from the same HeLa cells by miRNA microarray analysis. Mitochondria were purified using a combination of cell fractionation and immunoisolation, and assessed for the lack of protein and RNA contaminants. We found 57 miRNAs differentially expressed in HeLa mitochondria and cytosol. Of these 57, a signature of 13 nuclear-encoded miRNAs was reproducibly enriched in mitochondrial RNA and validated by RT-PCR for hsa-miR-494, hsa-miR-1275 and hsa-miR-1974. This study provides the first comprehensive view of the localization of RNA interference components to the mitochondria. Our data outline the molecular bases for a novel layer of crosstalk between nucleus and mitochondria through a specific subset of human miRNAs that we termed ‘mitomiRs’. To assess whether nuclear-encoded miRNA are detectable in human mitochondria, we performed the following four steps approach. First, cultured HeLa cells were allowed to reach 80-100% confluence and subjected to fractionation in order to isolate the cytosolic fraction. From the same HeLa cells, mitochondria were isolated by immunomagnetic Anti-TOM22 MicroBeads from the Mitochondria Isolation Kit (Miltenyi Biotec). In total, six mitochondria preparations were perfromed, three of these were additionally treated with RNase A. Second, total RNA was extracted from the mitochondrial and cytosolic fractions. Third, mitochondrial and cytosolic RNA were respectively profiled by microRNA microarray analysis. Last, data were analyzed and normalized.Three independent assays were performed.

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Human mitochondria hub of small RNAs: Analysis by deep Sequencing

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