scholarly journals Control of ribosomal protein synthesis by the Microprocessor complex

2021 ◽  
Vol 14 (671) ◽  
pp. eabd2639
Author(s):  
Xuan Jiang ◽  
Amit Prabhakar ◽  
Stephanie M. Van der Voorn ◽  
Prajakta Ghatpande ◽  
Barbara Celona ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Ribosomal Protein ◽  
Nuclear Export ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Cellular Growth ◽  
Ribosomal Protein Genes ◽  
Erythroid Progenitors ◽  
Microprocessor Complex ◽  
Ribosomal Protein Synthesis

Ribosome biogenesis in eukaryotes requires the coordinated production and assembly of 80 ribosomal proteins and four ribosomal RNAs (rRNAs), and its rate must be synchronized with cellular growth. Here, we showed that the Microprocessor complex, which mediates the first step of microRNA processing, potentiated the transcription of ribosomal protein genes by eliminating DNA/RNA hybrids known as R-loops. Nutrient deprivation triggered the nuclear export of Drosha, a key component of the Microprocessor complex, and its subsequent degradation by the E3 ubiquitin ligase Nedd4, thereby reducing ribosomal protein production and protein synthesis. In mouse erythroid progenitors, conditional deletion of Drosha led to the reduced production of ribosomal proteins, translational inhibition of the mRNA encoding the erythroid transcription factor Gata1, and impaired erythropoiesis. This phenotype mirrored the clinical presentation of human “ribosomopathies.” Thus, the Microprocessor complex plays a pivotal role in synchronizing protein synthesis capacity with cellular growth rate and is a potential drug target for anemias caused by ribosomal insufficiency.

scholarly journals Control of ribosomal protein synthesis by Microprocessor complex

2020 ◽  
Author(s):  
Xuan Jiang ◽  
Amit Prabhakar ◽  
Stephanie M. Van der Voorn ◽  
Prajakta Ghatpande ◽  
Barbara Celona ◽  
...  
Keyword(s):  
Cell Growth ◽  
Nuclear Export ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Cellular Growth ◽  
New Paradigm ◽  
Erythroid Progenitors ◽  
Conditional Deletion ◽  
Microprocessor Complex ◽  
Ribosomal Protein Synthesis

AbstractRibosome biogenesis in eukaryotes requires stoichiometric production and assembly of 80 ribosomal proteins (RPs) and 4 ribosomal RNAs, and its rate must be coordinated with cellular growth. The indispensable regulator of RP biosynthesis is the 5’-terminal oligopyrimidine (TOP) motif, spanning the transcription start site of all RP genes. Here we show that the Microprocessor complex, previously linked to the first step of processing microRNAs (miRNAs), coregulates RP expression by binding the TOP motif of nascent RP mRNAs and stimulating transcription elongation via resolution of DNA/RNA hybrids. Cell growth arrest triggers nuclear export and degradation of the Microprocessor protein Drosha by the E3 ubiquitin ligase Nedd4, accumulation of DNA/RNA hybrids at RP gene loci, decreased RP synthesis, and ribosome deficiency, hence synchronizing ribosome production with cell growth. Conditional deletion of Drosha in erythroid progenitors phenocopies human ribosomopathies, in which ribosomal insufficiency leads to anemia. Outlining a miRNA-independent role of the Microprocessor complex at the interphase between cell growth and ribosome biogenesis offers a new paradigm by which cells alter their protein biosynthetic capacity and cellular metabolism.

scholarly journals Effect of heat shock on ribosome synthesis in Drosophila melanogaster.

1988 ◽  
Vol 8 (1) ◽  
pp. 91-95 ◽  
Author(s):  
J Bell ◽  
L Neilson ◽  
M Pellegrini
Keyword(s):  
Tissue Culture ◽  
Protein Synthesis ◽  
Drosophila Melanogaster ◽  
Heat Shock ◽  
Ribosomal Protein ◽  
Ribosomal Proteins ◽  
Culture Cells ◽  
Tissue Culture Cells ◽  
Ribosomal Protein Synthesis ◽  
Correct Processing

In Drosophila tissue culture cells, the synthesis of ribosomal proteins was inhibited by a 1-h 37 degrees C heat shock. Ribosomal protein synthesis was repressed to a greater extent than that of most other proteins synthesized by these cells at 25 degrees C. After a 1-h heat shock, when the cells were returned to 25 degrees C, the ribosomal proteins were much slower than most other 25 degrees C proteins to return to pre-heat shock levels of synthesis. Relative to one another, all the ribosomal proteins were inhibited and later recovered to normal levels of synthesis at the same rate and to the same extent. Unlike the ribosomal proteins, the precursor to the large rRNAs was continually synthesized during heat shock, although at a slightly reduced level, but was not processed. It was rapidly degraded, with a half-life of approximately 16 min. Pre-heat shock levels of synthesis, stability, and correct processing were restored only when ribosomal protein synthesis returned to at least 50% of that seen in non-heat-shocked cells.

Regulation of Ribosomal Protein mRNA Content and Translation in Growth-Stimulated Mouse Fibroblasts

1982 ◽  
Vol 2 (6) ◽  
pp. 685-693
Author(s):  
Pamela K. Geyer ◽  
Oded Meyuhas ◽  
Robert P. Perry ◽  
Lee F. Johnson
Keyword(s):  
Protein Synthesis ◽  
Ribosomal Protein ◽  
Ribosomal Proteins ◽  
Growth Stimulation ◽  
Growth Conditions ◽  
Resting Cells ◽  
Serum Stimulation ◽  
Mrna Content ◽  
Ribosomal Protein Synthesis ◽  
Polyadenylated Mrna

When resting (G 0 ) mouse 3T6 fibroblasts are serum stimulated to reenter the cell cycle, the rates of synthesis of rRNA and ribosomal proteins increase, resulting in an increase in ribosome content beginning about 6 h after stimulation. In this study, we monitored the content, metabolism, and translation of ribosomal protein mRNA (rp mRNA) in resting, exponentially growing, and serum-stimulated 3T6 cells. Cloned cDNAs for seven rp mRNAs were used in DNA-excess filter hybridization studies to assay rp mRNA. We found that about 85% of rp mRNA is polyadenylated under all growth conditions. The rate of labeling of rp mRNA relative to total polyadenylated mRNA changed very little after stimulation. The half-life of rp mRNA was about 11 h in resting cells and about 8 h in exponentially growing cells, values which are similar to the half-lives of total mRNA in resting and growing cells (about 9 h). The content of rp mRNA relative to total mRNA was about the same in resting and growing 3T6 cells. Furthermore, the total amount of rp mRNA did not begin to increase until about 6 h after stimulation. Since an increase in rp mRNA content did not appear to be responsible for the increase in ribosomal protein synthesis, we determined the efficiency of translation of rp mRNA under different conditions. We found that about 85% of pulse-labeled rp mRNA was associated with polysomes in exponentially growing cells. In resting cells, however, only about half was associated with polysomes, and about 30% was found in the monosomal fraction. The distribution shifted to that found in growing cells within 3 h after serum stimulation. Similar results were obtained when cells were labeled for 10.5 h. About 70% of total polyadenylated mRNA was in the polysome fraction in all growth states regardless of labeling time, indicating that the shift in mRNA distribution was species specific. These results indicate that the content and metabolism of rp mRNA do not change significantly after growth stimulation. The rate of ribosomal protein synthesis appears to be controlled during the resting-growing transition by an alteration of the efficiency of translation of rp mRNA, possibly at the level of protein synthesis initiation.

scholarly journals Regulation of Ribosomal Protein mRNA Content and Translation in Growth-Stimulated Mouse Fibroblasts

1982 ◽  
Vol 2 (6) ◽  
pp. 685-693 ◽  
Author(s):  
Pamela K. Geyer ◽  
Oded Meyuhas ◽  
Robert P. Perry ◽  
Lee F. Johnson
Keyword(s):  
Protein Synthesis ◽  
Ribosomal Protein ◽  
Ribosomal Proteins ◽  
Growth Stimulation ◽  
Growth Conditions ◽  
Resting Cells ◽  
Serum Stimulation ◽  
Mrna Content ◽  
Ribosomal Protein Synthesis ◽  
Polyadenylated Mrna

When resting (G0) mouse 3T6 fibroblasts are serum stimulated to reenter the cell cycle, the rates of synthesis of rRNA and ribosomal proteins increase, resulting in an increase in ribosome content beginning about 6 h after stimulation. In this study, we monitored the content, metabolism, and translation of ribosomal protein mRNA (rp mRNA) in resting, exponentially growing, and serum-stimulated 3T6 cells. Cloned cDNAs for seven rp mRNAs were used in DNA-excess filter hybridization studies to assay rp mRNA. We found that about 85% of rp mRNA is polyadenylated under all growth conditions. The rate of labeling of rp mRNA relative to total polyadenylated mRNA changed very little after stimulation. The half-life of rp mRNA was about 11 h in resting cells and about 8 h in exponentially growing cells, values which are similar to the half-lives of total mRNA in resting and growing cells (about 9 h). The content of rp mRNA relative to total mRNA was about the same in resting and growing 3T6 cells. Furthermore, the total amount of rp mRNA did not begin to increase until about 6 h after stimulation. Since an increase in rp mRNA content did not appear to be responsible for the increase in ribosomal protein synthesis, we determined the efficiency of translation of rp mRNA under different conditions. We found that about 85% of pulse-labeled rp mRNA was associated with polysomes in exponentially growing cells. In resting cells, however, only about half was associated with polysomes, and about 30% was found in the monosomal fraction. The distribution shifted to that found in growing cells within 3 h after serum stimulation. Similar results were obtained when cells were labeled for 10.5 h. About 70% of total polyadenylated mRNA was in the polysome fraction in all growth states regardless of labeling time, indicating that the shift in mRNA distribution was species specific. These results indicate that the content and metabolism of rp mRNA do not change significantly after growth stimulation. The rate of ribosomal protein synthesis appears to be controlled during the resting-growing transition by an alteration of the efficiency of translation of rp mRNA, possibly at the level of protein synthesis initiation.

scholarly journals Human Ribosomal Proteins RPeL27, RPeL43, and RPeL41 Are Upregulated in Nasopharyngeal Carcinoma Cell Lines

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Edmund Ui-Hang Sim ◽  
Stella Li-Li Chan ◽  
Kher-Lee Ng ◽  
Choon-Weng Lee ◽  
Kumaran Narayanan
Keyword(s):  
Nasopharyngeal Carcinoma ◽  
Ribosomal Protein ◽  
Cell Lines ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Expression Patterns ◽  
Transcript Level ◽  
Ribosomal Protein Genes ◽  
Significant Differential Expression ◽  
Protein Levels

Apart from their canonical role in ribosome biogenesis, there is increasing evidence of ribosomal protein genes’ involvement in various cancers. A previous study by us revealed significant differential expression of three ribosomal protein genes (RPeL27, RPeL41, and RPeL43) between cell lines derived from tumor and normal nasopharyngeal epithelium. However, the results therein were based on a semiquantitative assay, thus preliminary in nature. Herein, we provide findings of a deeper analysis of these three genes in the context to nasopharyngeal carcinoma (NPC) tumorigenesis. Their expression patterns were analyzed in a more quantitative manner at transcript level. Their protein expression levels were also investigated. We showed results that are contrary to previous report. Rather than downregulation, these genes were significantly overexpressed in NPC cell lines compared to normal control at both transcript and protein levels. Nevertheless, their association with NPC has been established. Immunoprecipitation pulldown assays indicate the plausible interaction of either RPeL27 or RPeL43 with POTEE/TUBA1A and ACTB/ACTBL2 complexes. In addition, RPeL43 is shown to bind with MRAS and EIF2S1 proteins in a NPC cell line (HK1). Our findings support RPeL27, RPeL41, and RPeL43 as potential markers of NPC and provide insights into the interaction targets of RPeL27 and RPeL43 proteins.

scholarly journals A novel stress response pathway regulates rRNA biogenesis

2020 ◽  
Author(s):  
Witold Szaflarski ◽  
Mateusz Sowiński ◽  
Marta Leśniczak ◽  
Sandeep Ojha ◽  
Anaïs Aulas ◽  
...  
Keyword(s):  
Stress Response ◽  
Ribosomal Protein ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Protein Translation ◽  
Rrna Processing ◽  
Stress Response Pathway ◽  
Cellular Translation ◽  
Response To Stress ◽  
Ribosomal Protein Synthesis

ABSTRACTProduction of ribosomes is an energy-intensive process owing to the intricacy of these massive macromolecular machines. Each human ribosome contains 80 ribosomal proteins and four non-coding RNAs. Accurate assembly requires precise regulation of protein and RNA subunits. In response to stress, the integrated stress response (ISR) rapidly inhibits global translation. How rRNA is coordinately regulated with the rapid inhibition of ribosomal protein synthesis is not known. Here we show that stress specifically inhibits the first step of rRNA processing. Unprocessed rRNA is stored within the nucleolus, and, when stress resolves, it re-enters the ribosome biogenesis pathway. Retention of unprocessed rRNA within the nucleolus aids in the maintenance of this organelle. This response is independent of the ISR or inhibition of cellular translation but represents an independent stress-response pathway that we term Ribosome Biogenesis Stress Response (RiBiSR). Failure to coordinately regulate ribosomal protein translation and rRNA production results in nucleolar fragmentation. Our study unveils a novel stress response pathway that aims at conserving energy, preserving the nucleolus, and prevents further stress by regulation of rRNA processing.

scholarly journals The roles of ribosomal proteins in nasopharyngeal cancer: culprits, sentinels or both

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Edmund Ui-Hang Sim ◽  
Choon-Weng Lee ◽  
Kumaran Narayanan
Keyword(s):  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Protein Biosynthesis ◽  
Physiological Activity ◽  
Nasopharyngeal Cancer ◽  
Protein Translation ◽  
Cellular Protein ◽  
Cellular Growth ◽  
Ribosomal Protein Genes ◽  
Relationship Of

AbstractRibosomal protein genes encode products that are essential for cellular protein biosynthesis and are major components of ribosomes. Canonically, they are involved in the complex system of ribosome biogenesis pivotal to the catalysis of protein translation. Amid this tightly organised process, some ribosomal proteins have unique spatial and temporal physiological activity giving rise to their extra-ribosomal functions. Many of these extra-ribosomal roles pertain to cellular growth and differentiation, thus implicating the involvement of some ribosomal proteins in organogenesis. Consequently, dysregulated functions of these ribosomal proteins could be linked to oncogenesis or neoplastic transformation of human cells. Their suspected roles in carcinogenesis have been reported but not specifically explained for malignancy of the nasopharynx. This is despite the fact that literature since one and half decade ago have documented the association of ribosomal proteins to nasopharyngeal cancer. In this review, we explain the association and contribution of dysregulated expression among a subset of ribosomal proteins to nasopharyngeal oncogenesis. The relationship of these ribosomal proteins with the cancer are explained. We provide information to indicate that the dysfunctional extra-ribosomal activities of specific ribosomal proteins are tightly involved with the molecular pathogenesis of nasopharyngeal cancer albeit mechanisms yet to be precisely defined. The complete knowledge of this will impact future applications in the effective management of nasopharyngeal cancer.

scholarly journals Hierarchy of elements regulating synthesis of ribosomal proteins in Saccharomyces cerevisiae.

1981 ◽  
Vol 1 (11) ◽  
pp. 1016-1023 ◽  
Author(s):  
D R Kief ◽  
J R Warner
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Synthesis ◽  
Ribosomal Protein ◽  
Ribonucleic Acid ◽  
Ribosomal Proteins ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Messenger Ribonucleic Acid ◽  
Ribosomal Protein Synthesis ◽  
Stimulation Of

Saccharomyces cerevisiae cells respond to a heat shock by temporarily slowing the synthesis of ribosomal proteins (C. Gorenstein and J. R. Warner, Proc. Natl. Acad. Sci. U.S.A. 73:1574-1551, 1976). When cultures growing oxidatively on ethanol as the sole carbon source were shifted from 23 to 36 degrees C, the synthesis of ribosomal proteins was coordinately inhibited twice as rapidly and 45% more severely than in comparable cultures growing fermentatively on glucose. Within 15 min, the relative rates of synthesis of at least 30 ribosomal proteins declined to less than one-sixth their initial values, whereas the overall rate of protein synthesis increased at least threefold. We suggest that this is due primarily to controls at the level of synthesis of messenger ribonucleic acid for ribosomal proteins but may also involve changes in messenger ribonucleic acid stability. In contrast, a nutritional shift-up causes a stimulation of the synthesis of ribosomal proteins. Experiments designed to determine the hierarchy of stimuli affecting the synthesis of these proteins demonstrated that temperature shock was dominant to glucose stimulation. When a culture growing on ethanol was shifted from 23 to 36 degrees C and glucose was added shortly afterward, the decline in ribosomal protein synthesis continued unabated. However, in wild-type cells ribosomal protein synthesis began to recover within 15 min. In mutants temperature sensitive for ribosome synthesis, e.g., rna2, there was no recovery in the synthesis of most ribosomal proteins, suggesting that the product of rna2 is essential for the production of these proteins under all vegetative conditions.

scholarly journals Translational initiation factor expression and ribosomal protein gene expression are repressed coordinately but by different mechanisms in murine lymphosarcoma cells treated with glucocorticoids.

1989 ◽  
Vol 9 (9) ◽  
pp. 3679-3684 ◽  
Author(s):  
S Huang ◽  
J W Hershey
Keyword(s):  
Gene Expression ◽  
Protein Synthesis ◽  
Ribosomal Protein ◽  
Ribosomal Proteins ◽  
Ribosomal Protein Gene ◽  
Initiation Factor ◽  
Mrna Levels ◽  
Translational Initiation ◽  
Ribosomal Protein Synthesis ◽  
Translational Initiation Factor

P1798 murine lymphosarcoma cells cease to proliferate upon exposure to 10(-7) M dexamethasone and exhibit a dramatic inhibition of rRNA and ribosomal protein synthesis (O. Meyuhas, E. Thompson, Jr., and R. P. Perry, Mol. Cell Biol. 7:2691-2699, 1987). These workers demonstrated that ribosomal protein synthesis is regulated primarily at the level of translation, since dexamethasone did not alter mRNA levels but shifted the mRNAs from active polysomes into inactive messenger ribonucleoproteins. We have examined the effects of dexamethasone on the biosynthesis of initiation factor proteins in the same cell line. The relative protein synthesis rates of eIF-4A and eIF-2 alpha were inhibited by about 70% by the hormone, a reduction comparable to that for ribosomal proteins. The mRNA levels of eIF-4A, eIF-4D, and eIF-2 alpha also were reduced by 60 to 70%, indicating that synthesis rates are proportional to mRNA concentrations. Analysis of polysome profiles showed that the average number of ribosomes per initiation factor polysome was only slightly reduced by dexamethasone, and little or no mRNA was present in messenger ribonucleoproteins. The results indicate that initiation factor gene expression is coordinately regulated with ribosomal protein synthesis but is controlled primarily by modulating mRNA levels rather than mRNA efficiency.

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