Role of mitochondrial ribosome-dependent translation in germline formation in Drosophila embryos

AbstractRibosome biogenesis requires auxiliary factors to promote folding and assembly of ribosomal proteins and RNA. Particularly, maturation of the peptidyl transferase center (PTC) is mediated by conserved GTPases, but the molecular basis is poorly understood. Here, we define the mechanism of GTPase-driven maturation of the human mitochondrial large ribosomal subunit (mtLSU) using endogenous complex purification, in vitro reconstitution and cryo-EM. Structures of transient native mtLSU assembly intermediates that accumulate in GTPBP6-deficient cells reveal how the biogenesis factors GTPBP5, MTERF4 and NSUN4 facilitate PTC folding. Addition of recombinant GTPBP6 reconstitutes late mtLSU biogenesis in vitro and shows that GTPBP6 triggers a molecular switch and progression to a near-mature PTC state. Additionally, cryo-EM analysis of GTPBP6-treated mature mitochondrial ribosomes reveals the structural basis for the dual-role of GTPBP6 in ribosome biogenesis and recycling. Together, these results provide a framework for understanding step-wise PTC folding as a critical conserved quality control checkpoint.

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Mitochondrial microRNAs: A Putative Role in Tissue Regeneration

Biology ◽

10.3390/biology9120486 ◽

2020 ◽

Vol 9 (12) ◽

pp. 486

Author(s):

Sílvia C. Rodrigues ◽

Renato M. S. Cardoso ◽

Filipe V. Duarte

Keyword(s):

Tissue Regeneration ◽

Protein Complexes ◽

Mitochondrial Protein ◽

Noncoding Rnas ◽

Atp Synthesis ◽

Mitochondrial Proteins ◽

Cellular Mechanisms ◽

Small Noncoding Rnas ◽

Mitochondrial Ribosome

The most famous role of mitochondria is to generate ATP through oxidative phosphorylation, a metabolic pathway that involves a chain of four protein complexes (the electron transport chain, ETC) that generates a proton-motive force that in turn drives the ATP synthesis by the Complex V (ATP synthase). An impressive number of more than 1000 mitochondrial proteins have been discovered. Since mitochondrial proteins have a dual genetic origin, it is predicted that ~99% of these proteins are nuclear-encoded and are synthesized in the cytoplasmatic compartment, being further imported through mitochondrial membrane transporters. The lasting 1% of mitochondrial proteins are encoded by the mitochondrial genome and synthesized by the mitochondrial ribosome (mitoribosome). As a result, an appropriate regulation of mitochondrial protein synthesis is absolutely required to achieve and maintain normal mitochondrial function. Regarding miRNAs in mitochondria, it is well-recognized nowadays that several cellular mechanisms involving mitochondria are regulated by many genetic players that originate from either nuclear- or mitochondrial-encoded small noncoding RNAs (sncRNAs). Growing evidence collected from whole genome and transcriptome sequencing highlight the role of distinct members of this class, from short interfering RNAs (siRNAs) to miRNAs and long noncoding RNAs (lncRNAs). Some of the mechanisms that have been shown to be modulated are the expression of mitochondrial proteins itself, as well as the more complex coordination of mitochondrial structure and dynamics with its function. We devote particular attention to the role of mitochondrial miRNAs and to their role in the modulation of several molecular processes that could ultimately contribute to tissue regeneration accomplishment.

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The role of the mitochondrial ribosome in human disease: searching for mutations in 12S mitochondrial rRNA with high disruptive potential

Human Molecular Genetics ◽

10.1093/hmg/ddt490 ◽

2013 ◽

Vol 23 (4) ◽

pp. 949-967 ◽

Cited By ~ 20

Author(s):

Paul M. Smith ◽

Joanna L. Elson ◽

Laura C. Greaves ◽

Saskia B. Wortmann ◽

Richard J.T. Rodenburg ◽

...

Keyword(s):

Human Disease ◽

Mitochondrial Rrna ◽

Mitochondrial Ribosome

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Essential role of mitochondrially encoded large rRNA for germ-line formation in Drosophila embryos

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.95.19.11274 ◽

1998 ◽

Vol 95 (19) ◽

pp. 11274-11278 ◽

Cited By ~ 61

Author(s):

T. Iida ◽

S. Kobayashi

Keyword(s):

Essential Role ◽

Germ Line ◽

Line Formation ◽

Drosophila Embryos

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Compartments, wingless and engrailed: patterning the ventral epidermis of Drosophila embryos

Development ◽

10.1242/dev.122.12.4095 ◽

1996 ◽

Vol 122 (12) ◽

pp. 4095-4103 ◽

Cited By ~ 14

Author(s):

P.A. Lawrence ◽

B. Sanson ◽

J.P. Vincent

Keyword(s):

Pattern Formation ◽

Wing Disc ◽

High Concentration ◽

Good Region ◽

Steep Slopes ◽

Cuticular Structures ◽

Different Levels ◽

Promote Cell Death ◽

Drosophila Embryos

Recent experiments on the wing disc of Drosophila have shown that cells at the interface between the anterior and posterior compartments drive pattern formation by becoming the source of a morphogen. Here we ask whether this model applies to the ventral embryonic epidermis. First, we show that interfaces between posterior (engrailed ON) and anterior (engrailed OFF) cells are required for pattern formation. Second, we provide evidence that Wingless could play the role of the morphogen, at least within part of the segmental pattern. We looked at the cuticular structures that develop after different levels of uniform Wingless activity are added back to unsegmented embryos (wingless- engrailed-). Because it is rich in landmarks, the T1 segment is a good region to analyse. There, we find that the cuticle formed depends on the amount of added Wingless activity. For example, a high concentration of Wingless gives the cuticle elements normally found near the top of the presumed gradient. Unsegmented embryos are much shorter than wild type. If Wingless activity is added in stripes, the embryos are longer than if it is added uniformly. We suggest that the Wingless gradient landscape affects the size of the embryo, so that steep slopes would allow cells to survive and divide, while an even distribution of morphogen would promote cell death. Supporting the hypothesis that Wingless acts as a morphogen, we find that these stripes affect, at a distance, the type of cuticle formed and the planar polarity of the cells.

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Early Spindle Assembly in Drosophila Embryos: Role of a Force Balance Involving Cytoskeletal Dynamics and Nuclear Mechanics

Molecular Biology of the Cell ◽

10.1091/mbc.e05-02-0154 ◽

2005 ◽

Vol 16 (10) ◽

pp. 4967-4981 ◽

Cited By ~ 51

Author(s):

E. N. Cytrynbaum ◽

P. Sommi ◽

I. Brust-Mascher ◽

J. M. Scholey ◽

A. Mogilner

Keyword(s):

Spindle Assembly ◽

Spindle Pole ◽

Cortical Reorganization ◽

Force Balance ◽

Cell Cortex ◽

Nuclear Dynamics ◽

Nuclear Mechanics ◽

Cytoskeletal Dynamics ◽

Drosophila Embryos

Mitotic spindle morphogenesis depends upon the action of microtubules (MTs), motors and the cell cortex. Previously, we proposed that cortical- and MT-based motors acting alone can coordinate early spindle assembly in Drosophila embryos. Here, we tested this model using microscopy of living embryos to analyze spindle pole separation, cortical reorganization, and nuclear dynamics in interphase-prophase of cycles 11-13. We observe that actin caps remain flat as they expand and that furrows do not ingress. As centrosomes separate, they follow a linear trajectory, maintaining a constant pole-to-furrow distance while the nucleus progressively deforms along the elongating pole-pole axis. These observations are incorporated into a model in which outward forces generated by zones of active cortical dynein are balanced by inward forces produced by nuclear elasticity and during cycle 13, by Ncd, which localizes to interpolar MTs. Thus, the force-balance driving early spindle morphogenesis depends upon MT-based motors acting in concert with the cortex and nucleus.

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Argos and Spitz group genes function to regulate midline glial cell number in Drosophila embryos

Development ◽

10.1242/dev.124.19.3787 ◽

1997 ◽

Vol 124 (19) ◽

pp. 3787-3796 ◽

Cited By ~ 2

Author(s):

C. Stemerdink ◽

J.R. Jacobs

Keyword(s):

Gene Expression ◽

Glial Cell ◽

Nerve Cord ◽

Egf Receptor ◽

Ectopic Expression ◽

Cell Number ◽

Glia Cell ◽

Drosophila Embryos

The midline glia of the Drosophila embryonic nerve cord undergo a reduction in cell number after facilitating commissural tract morphogenesis. The numbers of midline glia entering apoptosis at this stage can be increased by a loss or reduction of function in genes of the spitz group or Drosophila EGF receptor (DER) pathway. Argos, a secreted molecule with an atypical EGF motif, is postulated to function as a DER antagonist. In this work, we assess the role of argos in the determination of midline glia cell number. Although all midline glia express DER, argos expression is restricted to the midline glia which do not enter apoptosis. Fewer midline glia enter apoptosis in embryos lacking argos function. Ectopic expression of argos is sufficient to remove all DER-expressing midline glia from the nerve cord, even those that already express argos. DER expression is not terminated in the midline glia after spitz group signaling triggers changes in gene expression. It is therefore likely that an attenuation of DER signaling by Argos is integrated with the augmentation of DER signaling by Spitz throughout the period of reduction of midline glia number. We suggest that signaling by Spitz but not Argos is restricted to adhesive junctions. In this manner, midline glia not forming signaling junctions remain sensitive to juxtacrine Argos signaling, while an autocrine Argos signal is excluded by the adhesive junction.

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The post-transcriptional life of mammalian mitochondrial RNA

Biochemical Journal ◽

10.1042/bj20112208 ◽

2012 ◽

Vol 444 (3) ◽

pp. 357-373 ◽

Cited By ~ 87

Author(s):

Joanna Rorbach ◽

Michal Minczuk

Keyword(s):

Messenger Rna ◽

Mitochondrial Gene ◽

Rna Stability ◽

Stability Control ◽

Mitochondrial Rna ◽

Mammalian Mitochondria ◽

Mitochondrial Ribosome ◽

Rna Maturation ◽

Rna Polyadenylation

Mammalian mitochondria contain their own genome that encodes mRNAs for thirteen essential subunits of the complexes performing oxidative phosporylation as well as the RNA components (two rRNAs and 22 tRNAs) needed for their translation in mitochondria. All RNA species are produced from single polycistronic precursor RNAs, yet the relative concentrations of various RNAs differ significantly. This underscores the essential role of post-transcriptional mechanisms that control the maturation, stability and translation of mitochondrial RNAs. The present review provides a detailed summary on the role of RNA maturation in the regulation of mitochondrial gene expression, focusing mainly on messenger RNA polyadenylation and stability control. Furthermore, the role of mitochondrial ribosomal RNA stability, processing and modifications in the biogenesis of the mitochondrial ribosome is discussed.

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Ran Is Required before Metaphase for Spindle Assembly and Chromosome Alignment and after Metaphase for Chromosome Segregation and Spindle Midbody Organization

Molecular Biology of the Cell ◽

10.1091/mbc.e05-10-0991 ◽

2006 ◽

Vol 17 (4) ◽

pp. 2069-2080 ◽

Cited By ~ 30

Author(s):

Rosalind V. Silverman-Gavrila ◽

Andrew Wilde

Keyword(s):

Chromosome Segregation ◽

Metaphase Plate ◽

Spindle Assembly ◽

Aurora A ◽

Microtubule Organization ◽

Chromosome Alignment ◽

Production Organization ◽

Drosophila Embryos

The Ran pathway has been shown to have a role in spindle assembly. However, the extent of the role of the Ran pathway in mitosis in vivo is unclear. We report that perturbation of the Ran pathway disrupted multiple steps of mitosis in syncytial Drosophila embryos and uncovered new mitotic processes that are regulated by Ran. During the onset of mitosis, the Ran pathway is required for the production, organization, and targeting of centrosomally nucleated microtubules to chromosomes. However, the role of Ran is not restricted to microtubule organization, because Ran is also required for the alignment of chromosomes at the metaphase plate. In addition, the Ran pathway is required for postmetaphase events, including chromosome segregation and the assembly of the microtubule midbody. The Ran pathway mediates these mitotic events, in part, by facilitating the correct targeting of the kinase Aurora A and the kinesins KLP61F and KLP3A to spindles.

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The Mesodermal Expression of rolling stone (rost) Is Essential for Myoblast Fusion in Drosophila and Encodes a Potential Transmembrane Protein

The Journal of Cell Biology ◽

10.1083/jcb.138.2.337 ◽

1997 ◽

Vol 138 (2) ◽

pp. 337-348 ◽

Cited By ~ 17

Author(s):

Achim Paululat ◽

Anette Goubeaud ◽

Christine Damm ◽

Stefan Knirr ◽

Susanne Burchard ◽

...

Keyword(s):

Transmembrane Protein ◽

Myoblast Fusion ◽

Fusion Process ◽

Knock Out ◽

Visceral Mesoderm ◽

Homologous Genes ◽

Rolling Stone ◽

Embryonic Nervous System ◽

Drosophila Embryos

In homozygous rolling stone embryos, the fusion of myoblasts to syncytial myotubes is diminished. Nevertheless, the visceral mesoderm, the heart mesoderm, and few somatic muscles are properly formed. Thus, we postulate a central role of rolling stone for the fusion process within the somatic mesoderm. We have cloned the rolling stone gene, and the deduced protein sequence is in accordance with a transmembrane protein, which agrees with the enrichment of Rost in the membrane fraction of Drosophila embryos. No homologous genes have been described so far. rolling stone is expressed in the embryonic nervous system and cells of the somatic mesoderm, most notable in muscle founder cells. To elucidate the function of rolling stone for myoblast fusion, we applied a knock-out strategy. The expression of an antisense rolling stone transcript specifically within the mesoderm of wild-type embryos results in fusion defects of myoblasts, proving that the rolling stone expression in the mesoderm is responsible for the rolling stone phenotype. We suggest that rolling stone is a member of a group of genes that are necessary for the fusion process during myogenesis.

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