Translational Regulation in the Mammalian Oocyte

Šušor, Andrej; Kubelka, Michal

doi:10.1007/978-3-319-60855-6_12

Cited by 30 publications

(32 citation statements)

References 246 publications

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“…Taken together, mTOR involvement is indispensable for inactivation of translational repressor 4E-BP1, which prevents the synthesis of essential proteins necessary for a correct completion of the meiotic and mitotic divisions. In addition to translational initiation factors, Ribosomal protein S3 (RPS3) is present at the mitotic 72 or newly forming meiotic spindle 73 . RPS3 knockdown causes arrest in mitotic metaphase, 72 which resembles the effect of mTOR inhibition 23 in the bovine oocyte.…”

Section: Resultsmentioning

confidence: 99%

Regulation of 4E-BP1 activity in the mammalian oocyte

et al. 2017

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Fully grown mammalian oocytes utilize transcripts synthetized and stored during earlier development. RNA localization followed by a local translation is a mechanism responsible for the regulation of spatial and temporal gene expression. Here we show that the mouse oocyte contains 3 forms of cap-dependent translational repressor expressed on the mRNA level: 4E-BP1, 4E-BP2 and 4E-BP3. However, only 4E-BP1 is present as a protein in oocytes, it becomes inactivated by phosphorylation after nuclear envelope breakdown and as such it promotes cap-dependent translation after NEBD. Phosphorylation of 4E-BP1 can be seen in the oocytes after resumption of meiosis but it is not detected in the surrounding cumulus cells, indicating that 4E-BP1 promotes translation at a specific cell cycle stage. Our immunofluorescence analyses of 4E-BP1 in oocytes during meiosis I showed an even localization of global 4E-BP1, as well as of its 4E-BP1 (Thr37/46) phosphorylated form. On the other hand, 4E-BP1 phosphorylated on Ser65 is localized at the spindle poles, and 4E-BP1 phosphorylated on Thr70 localizes on the spindle. We further show that the main positive regulators of 4E-BP1 phosphorylation after NEBD are mTOR and CDK1 kinases, but not PLK1 kinase. CDK1 exerts its activity toward 4E-BP1 phosphorylation via phosphorylation and activation of mTOR. Moreover, both CDK1 and phosphorylated mTOR co-localize with 4E-BP1 phosphorylated on Thr70 on the spindle at the onset of meiotic resumption. Expression of the dominant negative 4E-BP1 mutant adversely affects translation and results in spindle abnormality. Taken together, our results show that the phosphorylation of 4E-BP1 promotes translation at the onset of meiosis to support the spindle assembly and suggest an important role of CDK1 and mTOR kinases in this process. We also show that the mTOR regulatory pathway is present in human oocytes and is likely to function in a similar way as in mouse oocytes.

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Section: Resultsmentioning

confidence: 99%

Regulation of 4E-BP1 activity in the mammalian oocyte

et al. 2017

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“…However, according to the P/NP ratio of EDTA-treated NEBD-stage oocyte, we could not confirm or exclude the possibility that there were no high-molecular-weight stored ribonucleoprotein particles (RNP) that co-sedimented with polysomes and thus contained both rRNA species. It has been shown that maternal RNPs are stored in distinct sub-cellular regions in the oocyte [36]. Indeed, microscopic studies have revealed RNP aggregates at the cortex and in fibrillar cytoplasmic lattices and the latter of which also contains inactive ribosomes [36,57].…”

Section: Discussionmentioning

confidence: 99%

“…It has been shown that maternal RNPs are stored in distinct sub-cellular regions in the oocyte [36]. Indeed, microscopic studies have revealed RNP aggregates at the cortex and in fibrillar cytoplasmic lattices and the latter of which also contains inactive ribosomes [36,57]. However, very little is known about their physical properties, complete protein composition nor their velocity sedimentation coefficients.…”

Section: Discussionmentioning

confidence: 99%

“…The meiotic maturation of oocytes, within this context, requires a tightly coordinated array of cellular and metabolic processes that includes the inhibition of cell death, remodelling of chromatin and preparation for the metabolic demands connected with the first mitotic division and subsequent fertilisation [34,35]. Accordingly, such processes are largely mediated by the pre-synthesised maternal mRNA stored in translationally-inactive ribonucleoprotein particles [36]. The ribosomal recruitment of specific and required mRNAs during oocyte maturation is controlled by a complex regulatory network involving a central role for the cytoplasmic polyadenylation of targeted transcripts at their 3 -end [37][38][39][40], leading to the creation of translational hotspots (under the influence of the mTOR-eIF4E signalling axis) essential for meiotic maturation [41].…”

Section: Introductionmentioning

confidence: 99%

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Identifying the Translatome of Mouse NEBD-Stage Oocytes via SSP-Profiling; A Novel Polysome Fractionation Method

Mašek

Llano

Gahurová

et al. 2020

IJMS

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Meiotic maturation of oocyte relies on pre-synthesised maternal mRNA, the translation of which is highly coordinated in space and time. Here, we provide a detailed polysome profiling protocol that demonstrates a combination of the sucrose gradient ultracentrifugation in small SW55Ti tubes with the qRT-PCR-based quantification of 18S and 28S rRNAs in fractionated polysome profile. This newly optimised method, named Scarce Sample Polysome Profiling (SSP-profiling), is suitable for both scarce and conventional sample sizes and is compatible with downstream RNA-seq to identify polysome associated transcripts. Utilising SSP-profiling we have assayed the translatome of mouse oocytes at the onset of nuclear envelope breakdown (NEBD)—a developmental point, the study of which is important for furthering our understanding of the molecular mechanisms leading to oocyte aneuploidy. Our analyses identified 1847 transcripts with moderate to strong polysome occupancy, including abundantly represented mRNAs encoding mitochondrial and ribosomal proteins, proteasomal components, glycolytic and amino acids synthetic enzymes, proteins involved in cytoskeleton organization plus RNA-binding and translation initiation factors. In addition to transcripts encoding known players of meiotic progression, we also identified several mRNAs encoding proteins of unknown function. Polysome profiles generated using SSP-profiling were more than comparable to those developed using existing conventional approaches, being demonstrably superior in their resolution, reproducibility, versatility, speed of derivation and downstream protocol applicability.

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“…The developmental processes, which include meiotic progression, oocyte to embryo transition, later spermatogenesis and early embryogenesis, require timely and strictly regulated transcriptional and translational control (Braun, ; Susor & Kubelka, ). For this purpose, newly transcribed precursor (pre)‐messenger RNAs (mRNAs) in the nucleus undergo a number of modifications such as capping, polyadenylation, and splicing in the germ cells and early embryos as is observed in eukaryotic cells (Barckmann & Simonelig, ; Piccioni, Zappavigna, & Verrotti, ).…”

Section: From Transcription To Translation In the Germ Cells And Earlmentioning

confidence: 99%

The translational functions of embryonic poly(A)‐binding protein during gametogenesis and early embryo development

Öztürk

2019

Molecular Reproduction Devel

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Embryonic poly(A)‐binding protein (EPAB) is an RNA‐binding protein that binds to the poly(A) tails and AU‐rich element at the 3′ ends of messenger RNA (mRNAs). The main functions of EPAB are to protect stored mRNAs from undergoing deadenylation and subsequent degradation and to be involved in their translational regulation during spermatogenesis, oogenesis, and early embryogenesis. Following the first characterization of Epab in the Xenopus oocytes and early embryos, spatial and temporal expression and potential roles of the Epab gene have been determined in the vertebrate germ cells and early embryos. In this review, we have comprehensively evaluated all studies in this field and discussed the particular functions of EPAB in the spermatogenic cells, oocytes, early embryos, and somatic cells in vertebrates.

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Translational Regulation in the Mammalian Oocyte

Cited by 30 publications

References 246 publications

Regulation of 4E-BP1 activity in the mammalian oocyte

Regulation of 4E-BP1 activity in the mammalian oocyte

Identifying the Translatome of Mouse NEBD-Stage Oocytes via SSP-Profiling; A Novel Polysome Fractionation Method

The translational functions of embryonic poly(A)‐binding protein during gametogenesis and early embryo development

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