Cytoplasm: Translational Apparatus

2014 ◽  
pp. 1-19
Author(s):  
Karen S. Browning
Keyword(s):  
Translational Apparatus

scholarly journals The Interaction of the Chaperonin Tailless Complex Polypeptide 1 (Tcp1) Ring Complex (Tric) with Ribosome-Bound Nascent Chains Examined Using Photo-Cross-Linking

2000 ◽  
Vol 149 (3) ◽  
pp. 591-602 ◽  
Author(s):  
Christine D. McCallum ◽  
Hung Do ◽  
Arthur E. Johnson ◽  
Judith Frydman
Keyword(s):  
Close Association ◽  
Cellular Proteins ◽  
Cross Linking ◽  
Exit Channel ◽  
Nascent Chain ◽  
Ring Complex ◽  
Cross Links ◽  
Oligomeric Complex ◽  
A Chain ◽  
Translational Apparatus

The eukaryotic chaperonin tailless complex polypeptide 1 (TCP1) ring complex (TRiC) (also called chaperonin containing TCP1 [CCT]) is a hetero-oligomeric complex that facilitates the proper folding of many cellular proteins. To better understand the manner in which TRiC interacts with newly translated polypeptides, we examined its association with nascent chains using a photo-cross-linking approach. To this end, a series of ribosome-bound nascent chains of defined lengths was prepared using truncated mRNAs. Photoactivatable probes were incorporated into these 35S- labeled nascent chains during translation. Upon photolysis, TRiC was cross-linked to ribosome-bound polypeptides exposing at least 50–90 amino acids outside the ribosomal exit channel, indicating that the chaperonin associates with much shorter nascent chains than indicated by previous studies. Cross-links were observed for nascent chains of the cytosolic proteins actin, luciferase, and enolase, but not to ribosome-bound preprolactin. The pattern of cross-links became more complex as the nascent chain increased in length. These results suggest a chain length–dependent increase in the number of TRiC subunits involved in the interaction that is consistent with the idea that the substrate participates in subunit-specific contacts with the chaperonin. Both ribosome isolation by centrifugation through sucrose cushions and immunoprecipitation with anti-puromycin antibodies demonstrated that the photoadducts form on ribosome-bound polypeptides. Our results indicate that TRiC/CCT associates with the translating polypeptide shortly after it emerges from the ribosome and suggest a close association between the chaperonin and the translational apparatus.

scholarly journals Maybe repressed mRNAs are not stored in the chromatoid body in mammalian spermatids

Reproduction ◽  
2011 ◽  
Vol 142 (3) ◽  
pp. 383-388 ◽  
Author(s):  
Kenneth C Kleene ◽  
Danielle L Cullinane
Keyword(s):  
Caenorhabditis Elegans ◽  
Mrna Translation ◽  
Mrna Localization ◽  
Structure And Function ◽  
Convincing Evidence ◽  
Chromatoid Body ◽  
P Granules ◽  
Accurate Indication ◽  
And Function ◽  
Translational Apparatus

The chromatoid body is a dynamic organelle that is thought to coordinate the cytoplasmic regulation of mRNA translation and degradation in mammalian spermatids. The chromatoid body is also postulated to function in repression of mRNA translation by sequestering dormant mRNAs where they are inaccessible to the translational apparatus. This review finds no convincing evidence that dormant mRNAs are localized exclusively in the chromatoid body. This discrepancy can be explained by two hypotheses. First, experimental artifacts, possibly related to peculiarities of the structure and function of the chromatoid body, preclude obtaining an accurate indication of mRNA localization. Second, mRNA is not stored in the chromatoid body, because, like perinuclear P granules in Caenorhabditis elegans, the chromatoid body functions as a center for mRNP remodeling and export to other cytoplasmic sites.

scholarly journals Coordinated Hibernation of Transcriptional and Translational Apparatus during Growth Transition ofEscherichia colito Stationary Phase

mSystems ◽  
2018 ◽  
Vol 3 (5) ◽  
Author(s):  
Hideji Yoshida ◽  
Tomohiro Shimada ◽  
Akira Ishihama
Keyword(s):  
Stationary Phase ◽  
Sigma Factor ◽  
Exponential Phase ◽  
Screening System ◽  
Content Type ◽  
Genome Expression ◽  
70S Ribosome ◽  
K 12 ◽  
Sigma Subunit ◽  
Translational Apparatus

ABSTRACTIn the process ofEscherichia coliK-12 growth from exponential phase to stationary, marked alteration takes place in the pattern of overall genome expression through modulation of both parts of the transcriptional and translational apparatus. In transcription, the sigma subunit with promoter recognition properties is replaced from the growth-related factor RpoD by the stationary-phase-specific factor RpoS. The unused RpoD is stored by binding with the anti-sigma factor Rsd. In translation, the functional 70S ribosome is converted to inactive 100S dimers through binding with the ribosome modulation factor (RMF). Up to the present time, the regulatory mechanisms of expression of these two critical proteins, Rsd and RMF, have remained totally unsolved. In this study, attempts were made to identify the whole set of transcription factors involved in transcription regulation of thersdandrmfgenes using the newly developed promoter-specific transcription factor (PS-TF) screening system. In the first screening, 74 candidate TFs with binding activity to both of thersdandrmfpromoters were selected from a total of 194 purified TFs. After 6 cycles of screening, we selected 5 stress response TFs, ArcA, McbR, RcdA, SdiA, and SlyA, for detailed analysisin vitroandin vivoof their regulatory roles. Results indicated that bothrsdandrmfpromoters are repressed by ArcA and activated by McbR, RcdA, SdiA, and SlyA. We propose the involvement of a number of TFs in simultaneous and coordinated regulation of the transcriptional and translational apparatus. By using genomic SELEX (gSELEX) screening, each of the five TFs was found to regulate not only thersdandrmfgenes but also a variety of genes for growth and survival.IMPORTANCEDuring the growth transition ofE. colifrom exponential phase to stationary, the genome expression pattern is altered markedly. For this alteration, the transcription apparatus is altered by binding of anti-sigma factor Rsd to the RpoD sigma factor for sigma factor replacement, while the translation machinery is modulated by binding of RMF to 70S ribosome to form inactive ribosome dimer. Using the PS-TF screening system, a number of TFs were found to bind to both thersdandrmfpromoters, of which the regulatory roles of 5 representative TFs (one repressor ArcA and the four activators McbR, RcdA, SdiA, and SlyA) were analyzed in detail. The results altogether indicated the involvement of a common set of TFs, each sensing a specific environmental condition, in coordinated hibernation of the transcriptional and translational apparatus for adaptation and survival under stress conditions.

scholarly journals Tailed giant Tupanvirus possesses the most complete translational apparatus of the known virosphere

2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Jônatas Abrahão ◽  
Lorena Silva ◽  
Ludmila Santos Silva ◽  
Jacques Yaacoub Bou Khalil ◽  
Rodrigo Rodrigues ◽  
...  
Keyword(s):  
Translational Apparatus

scholarly journals Evolution of Mycolic Acid Biosynthesis Genes and Their Regulation during Starvation in Mycobacterium tuberculosis

2015 ◽  
Vol 197 (24) ◽  
pp. 3797-3811 ◽  
Author(s):  
Stevie Jamet ◽  
Yves Quentin ◽  
Coralie Coudray ◽  
Pauline Texier ◽  
Françoise Laval ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Outer Membrane ◽  
Cell Envelope ◽  
Stringent Response ◽  
Mycolic Acid ◽  
Content Type ◽  
New Targets ◽  
Key Enzyme ◽  
Unique Cell ◽  
Translational Apparatus

ABSTRACTMycobacterium tuberculosis, the etiological agent of tuberculosis, is a Gram-positive bacterium with a unique cell envelope composed of an essential outer membrane. Mycolic acids, which are very-long-chain (up to C100) fatty acids, are the major components of this mycomembrane. The enzymatic pathways involved in the biosynthesis and transport of mycolates are fairly well documented and are the targets of the major antituberculous drugs. In contrast, only fragmented information is available on the expression and regulation of the biosynthesis genes. In this study, we report that thehadA,hadB, andhadCgenes, which code for the mycolate biosynthesis dehydratase enzymes, are coexpressed with three genes that encode proteins of the translational apparatus. Consistent with the well-established control of the translation potential by nutrient availability, starvation leads to downregulation of thehadABCgenes along with most of the genes required for the synthesis, modification, and transport of mycolates. The downregulation of a subset of the biosynthesis genes is partially dependent on RelMtb, the key enzyme of the stringent response. We also report the phylogenetic evolution scenario that has shaped the current genetic organization, characterized by the coregulation of thehadABCoperon with genes of the translational apparatus and with genes required for the modification of the mycolates.IMPORTANCEMycobacterium tuberculosisinfects one-third of the human population worldwide, and despite the available therapeutic arsenal, it continues to kill millions of people each year. There is therefore an urgent need to identify new targets and develop a better understanding of how the bacterium is adapting itself to host defenses during infection. A prerequisite of this understanding is knowledge of how this adaptive skill has been implanted by evolution. Nutrient scarcity is an environmental condition the bacterium has to cope with during infection. In many bacteria, adaptation to starvation relies partly on the stringent response.M. tuberculosis's unique outer membrane layer, the mycomembrane, is crucial for its viability and virulence. Despite its being the target of the major antituberculosis drugs, only scattered information exists on how the genes required for biosynthesis of the mycomembrane are expressed and regulated during starvation. This work has addressed this issue as a step toward the identification of new targets in the fight againstM. tuberculosis.

Trypanosoma brucei mitochondrial ribonucleoprotein complexes which contain 12S and 9S ribosomal RNAs

Parasitology ◽  
1998 ◽  
Vol 116 (2) ◽  
pp. 157-164 ◽  
Author(s):  
H. H. SHU ◽  
H. U. GÖRINGER
Keyword(s):  
Cell Membrane ◽  
Trypanosoma Brucei ◽  
Translation System ◽  
12S Rrna ◽  
Translation Inhibition ◽  
Translational Activity ◽  
Ribonucleoprotein Complexes ◽  
Rnp Complex ◽  
Synthesis Activity ◽  
Translational Apparatus

Antibiotics have been widely used to identify ribosomal activity in Trypanosoma brucei mitochondria. The validity of some of the results has been questioned because the permeability of the trypanosome cell membrane for some antibiotics was not adequately addressed. Here we describe translation inhibition experiments with digitonin-permeabilized trypanosomes to exclude diffusion barriers through the cell membrane. Using this system we were able to confirm, next to the eukaryotic and thus cycloheximide-sensitive translation system, the existence of a prokaryotic-type translational activity being cycloheximide resistant, chloramphenicol sensitive and streptomycin dependent. We interpret this observation analogous to what has been found for other eukarya as the independent protein synthesis activity of the mitochondrial organelle. We further examined the putative translational apparatus by using isokinetic density-gradient analysis of mitochondrial extracts. The 2 mitochondrially encoded rRNAs, the 9S and 12S rRNAs, were found to co-fractionate in a single RNP complex, approximately 80S in size. This complex disassembled at reduced MgCl2 concentrations into 2 unusually small complexes of 17·5S, containing the 9S rRNA, and 20S containing the 12S rRNA. A preliminary stoichiometry determination suggested a multicopy assembly of these putative subunits in a 2[ratio ]3 ratio (20S[ratio ]17·5S).

Translation inhibition during the induction of apoptosis: RNA or protein degradation?

2004 ◽  
Vol 32 (4) ◽  
pp. 606-610 ◽  
Author(s):  
M. Bushell ◽  
M. Stoneley ◽  
P. Sarnow ◽  
A.E. Willis
Keyword(s):  
Protein Synthesis ◽  
Cellular Level ◽  
Translation Inhibition ◽  
Initiation Factors ◽  
Translation Initiation Factors ◽  
Inhibition Of Protein Synthesis ◽  
Induction Of Apoptosis ◽  
Global Increase ◽  
Translational Apparatus ◽  
Temporally Correlated

The induction of apoptosis leads to a substantial inhibition of protein synthesis. During this process changes to the translation-initiation factors, the ribosome and the cellular level of mRNA have been documented. However, it is by no means clear which of these events are necessary to achieve translational shutdown. In this article, we discuss modifications to the translational apparatus that occur during apoptosis and examine the potential contributions that they make to the inhibition of protein synthesis. Moreover, we present evidence that suggests that a global increase in the rate of mRNA degradation occurs before the caspase-dependent cleavage of initiation factors. Increased mRNA decay is temporally correlated with the shutdown of translation and therefore plays a major role in the inhibition of protein synthesis in apoptotic cells.

scholarly journals Homeostatic scaling is driven by a translation-dependent degradation axis that recruits miRISC remodelling

2020 ◽  
Author(s):  
Balakumar Srinivasan ◽  
Sarbani Samaddar ◽  
Sivaram V.S. Mylavarapu ◽  
James P. Clement ◽  
Sourav Banerjee
Keyword(s):  
Ampa Receptors ◽  
26S Proteasome ◽  
Network Activity ◽  
Degradation Mechanisms ◽  
Subsequent Removal ◽  
Ternary Interaction ◽  
Synaptic Homeostasis ◽  
Subsequent Degradation ◽  
The Individual ◽  
Translational Apparatus

AbstractHomeostatic scaling in neurons has been majorly attributed to the individual contribution of either translation or degradation; however there remains limited insight towards understanding how the interplay between the two processes effectuates synaptic homeostasis. Here, we report that a co-dependence between the translation and degradation mechanisms drives synaptic homeostasis whereas abrogation of either prevents it. Coordination between the two processes is achieved through the formation of a tripartite complex between translation regulators, the 26S proteasome and the miRNA-induced-silencing-complex (miRISC) components such as MOV10 and Trim32 on actively translating transcripts or polysomes. Disruption of polysomes abolishes this ternary interaction, suggesting that translating RNAs facilitate the combinatorial action of the proteasome and the translational apparatus. We identify that synaptic downscaling involves miRISC remodelling which entails the mTOR-dependent translation of Trim32, an E3 ligase and the subsequent degradation of its target, MOV10. MOV10 degradation is sufficient to invoke downscaling by enhancing Arc expression and causing the subsequent removal of post-synaptic AMPA receptors. We propose a mechanism that exploits a translation-driven degradation paradigm to invoke miRISC remodelling and induce homeostatic scaling during chronic network activity.

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