Identification of mecciRNAs and their roles in the mitochondrial entry of proteins
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus Danio rerio Homo sapiens
PROVIDER: GSE144063 | GEO | 2020/01/23
REPOSITORIES: GEO
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Project description:Current evidence suggests that nuclear-encoded mitochondrial proteins can be locally translated at the mitochondrial surface and co-translationally or post-translationally imported into mitochondria. mRNA localization on the mitochondrial membrane, a prerequisite for localized translation, remains uncharacterized in higher eukaryotic organisms. We employed fractionation-sequencing to profile mitochondria-associated mRNAs in zebrafish larvae. Our transcriptome-wide analysis reveals the localization of mRNAs of only 12% of the nuclear-encoded mitochondrial proteins to the mitochondrial surface, which suggests that post-translational import is the dominant mode of protein import to mitochondria. Additionally, the mRNAs which were localized to the mitochondrial membrane consisted mostly of those encoding proteins involved in mitochondrial dynamics, suggesting their site-specific translation. Finally, we show that the loss of function of the MIA pathway responsible for the post-translational import of a subclass of mitochondrial proteins, triggers mitochondrial localization of mRNAs encoding proteins that are imported to mitochondria via other pathways. Thus, our study suggests that mRNA targeting and localized translation could be relevant in higher eukaryotes to combat stress conditions affecting mitochondrial biogenesis in general.
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Project description:The human mitochondrial genome comprises a distinct genetic system transcribed as precursor polycistronic transcripts that are subsequently cleaved to generate individual mRNAs, tRNAs and rRNAs. Here we provide a comprehensive analysis of the human mitochondrial transcriptome across multiple cell lines and tissues. Using directional deep sequencing and parallel analysis of RNA ends, we demonstrate wide variation in mitochondrial transcript abundance, and precisely resolve transcript processing and maturation events. We identify novel transcripts, including small RNAs, and observe the enrichment of several nuclear RNAs in mitochondria. Using high-throughput in vivo DNaseI footprinting, we establish the global profile of DNA-binding protein occupancy across the mitochondrial genome at single nucleotide resolution, revealing novel regulatory features at mitochondrial transcription initiation sites and functional insights into disease-associated variants. Together, this integrated analysis of the mitochondrial transcriptome reveals unexpected complexity in the regulation, expression, and processing of mitochondrial RNA, and itM-CM-^BM-BM- provides a resource for the future study of mitochondrial function (accessed at mitochondria.matticklab.com). Examination of the mitochondiral transcriptome by long and small RNA sequencing, PARE sequencing and DNAseI hypersensitivity mapping.
2011-07-20 | E-GEOD-30772 | biostudies-arrayexpress
Project description:Identification of mecciRNAs and their roles in the mitochondrial entry of proteins
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Project description:The synthesis of mitochondrial OXPHOS complexes is central to cellular metabolism, yet many molecular details of mitochondrial translation remain elusive. It is commonly held view that translation initiation in human mitochondria proceeded in a manner similar to bacterial systems, with the mitoribosomal small subunit bound to the initiation factors, mtIF2 and mtIF3, along with initiator tRNA and an mRNA. However, unlike in bacteria, most human mitochondrial mRNAs lack 5′ leader sequences that can mediate small subunit binding, raising the question of how leaderless mRNAs are recognized by mitoribosomes. By using novel in vitro mitochondrial translation initiation assays, alongside biochemical and genetic characterization of cellular knockouts of mitochondrial translation factors, we describe unique features of translation initiation in human mitochondria. We show that in vitro, leaderless mRNA transcripts can be loaded directly onto assembled 55S mitoribosomes, but not onto the mitoribosomal small subunit (28S). In addition, we demonstrate that while mtIF2 is indispensable for mitochondrial translation, mtIF3 activity is not required for translation of leaderless mitochondrial transcripts but is essential for translation of ATP6 in the case of the bicistronic ATP8/ATP6 transcript. Our results confirm important evolutionary divergences of the mitochondrial translation system, and further our understanding of a process central to eukaryotic metabolism.
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Project description:Circular RNAs (circRNAs) are widespread circular forms of non-coding RNAs with largely unknown function. Because stimulation of mammary cells with the epidermal growth factor (EGF) leads to dynamic changes in the abundance of both coding and non-coding RNA molecules, and culminates in the acquisition of a robust migratory phenotype, this cellular model might disclose functions of circRNAs. Here we show that circRNAs of EGF-stimulated mammary cells are stably expressed, while mRNAs and micro-RNAs change within minutes. In general, the circRNAs we detected are relatively long-lived and weakly expressed. Interestingly, they are almost ubiquitously co-expressed with the corresponding linear transcripts, and the respective, shared promoter regions are more active compared to genes producing linear isoforms only. These findings imply that altered abundance of circRNAs, unlike changes in the levels of other RNAs, might not play critical roles in signaling cascades and downstream transcriptional networks that rapidly commit cells to specific outcomes. Detection of circRNAs from RNA-Seq â triplicate
2015-12-17 | E-GEOD-71195 | biostudies-arrayexpress
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.
2011-10-05 | E-GEOD-24761 | biostudies-arrayexpress
Project description:Circular RNAs (circRNAs) are widespread circular forms of non-coding RNAs with largely unknown function. Because stimulation of mammary cells with the epidermal growth factor (EGF) leads to dynamic changes in the abundance of both coding and non-coding RNA molecules, and culminates in the acquisition of a robust migratory phenotype, this cellular model might disclose functions of circRNAs. Here we show that circRNAs of EGF-stimulated mammary cells are stably expressed, while mRNAs and micro-RNAs change within minutes. In general, the circRNAs we detected are relatively long-lived and weakly expressed. Interestingly, they are almost ubiquitously co-expressed with the corresponding linear transcripts, and the respective, shared promoter regions are more active compared to genes producing linear isoforms only. These findings imply that altered abundance of circRNAs, unlike changes in the levels of other RNAs, might not play critical roles in signaling cascades and downstream transcriptional networks that rapidly commit cells to specific outcomes. Histone 3 Lysine 27 Acetylation â 2 replicates
2015-12-17 | E-GEOD-71196 | biostudies-arrayexpress
Project description:The human mitochondrial genome comprises a distinct genetic system transcribed as precursor polycistronic transcripts that are subsequently cleaved to generate individual mRNAs, tRNAs and rRNAs. Here we provide a comprehensive analysis of the human mitochondrial transcriptome across multiple cell lines and tissues. Using directional deep sequencing and parallel analysis of RNA ends, we demonstrate wide variation in mitochondrial transcript abundance, and precisely resolve transcript processing and maturation events. We identify novel transcripts, including small RNAs, and observe the enrichment of several nuclear RNAs in mitochondria. Using high-throughput in vivo DNaseI footprinting, we establish the global profile of DNA-binding protein occupancy across the mitochondrial genome at single nucleotide resolution, revealing novel regulatory features at mitochondrial transcription initiation sites and functional insights into disease-associated variants. Together, this integrated analysis of the mitochondrial transcriptome reveals unexpected complexity in the regulation, expression, and processing of mitochondrial RNA, and it provides a resource for the future study of mitochondrial function (accessed at mitochondria.matticklab.com).
2011-07-20 | GSE30772 | GEO
Project description:Identification of mitochondrial RNAs [II]
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Project description:Identification of mitochondrial RNAs [1]
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