Regulation Of Ribosomal Synthesis Research Articles

Regulator of Ribosome Synthesis 1 (RRS1) Stabilizes GRP78 and Promotes Breast Cancer Progression.

Regulator of ribosome synthesis 1 (RRS1), a crucial regulatory factor in ribosome biogenesis, exerts a remarkable impact on the progression of breast cancer (BC). However, the exact mechanisms and pathways have not yet been fully elucidated. To investigate the impact of RRS1 on BC growth and metastasis, along with its underlying mechanisms. We discovered that RRS1 is overexpressed in BC tissues and cell lines. This study aims to regulate the level of RRS1 through lentiviral transfection technology to explore its potential function in BC cells. Knockdown of RRS1 resulted in the inhibition of cell proliferation, invasion, and migration, whereas overexpression had the opposite effects. We firstly identified the interaction between RRS1 and Glucose-Regulated Protein 78 (GRP78) using Co-immunoprecipitation (Co-IP) combined with mass spectrometry analysis, providing evidences of co-localization and positive regulation between RRS1 and GRP78. We observed that RRS1 inhibited the degradation of GRP78 through the ubiquitin-proteasome pathway, resulting in the stabilization of GRP78. In addition, our findings suggested that RRS1 promoted BC progression by activating the GRP78-mediated phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway. In conclusion, this newly discovered RRS1/GRP78 signaling axis provides a molecular and theoretical basis for further exploring the mechanisms of breast cancer invasion and metastasis.

Downregulated RRS1 inhibits invasion and metastasis of BT549 through RPL11‑c‑Myc‑SNAIL axis.

Regulator of ribosome synthesis 1 (RRS1) is a key factor in ribosome biosynthesis and other cellular functions. High level of RRS1 in breast cancer cell lines is associated with increased cell proliferation, invasion and migration. RRS1 controls the assembly of the 60s subunit and maturation of 25S rRNA during ribosome biosynthesis. In this study, lentiviral transfection of sh-RNA was used to knock down the level of RRS1, to detect the effect of RRS1 on cell function and to explore the specific mechanism of RRS1 affecting cell invasion and metastasis by COIP and dual-luciferase reporter gene assays. The present study found that RRS1 knockdown reduced the accumulation of ribosome protein L11 (RPL11) in the nucleolus, which then migrated to the nucleoplasm and bound to c-Myc. This inhibited trans-activation of SNAIL by c-Myc and eventually decreased the invasion and metastasis capacity of the human breast cancer cell line BT549. Taken together, RRS1 regulates invasion and metastasis of human breast cancer cells through the RPL11-c-Myc-SNAIL axis. The findings are of great significance for exploring the mechanism of breast cancer invasion and metastasis and the corresponding regulatory factors.

Regulator of Ribosome Synthesis 1 Influences the Proliferation, Migration, and Invasion of Ovarian Cancer Cells

We investigated the effects of silencing the regulator of ribosome synthesis 1 (RRS1) gene on the proliferation, migration, and invasion of ovarian carcinoma cells, and its possible role in modulating signal transduction in these cells. Normal ovarian epithelial cell line IOSE80 was used as a control. We examined the mRNA and protein level of RRS1 using qRT-PCR and western blot in control and ovarian carcinoma cells (SKOV-3, SW626, and CAOV3). RNA interference technology was used to knockdown RRS1 expression in CAOV3 cells. MTT was used to examine the proliferation of these cells, while a Transwell assay was used to assay the cells’ migration and invasion abilities. Western blot was used to measure the levels of CyclinD1, P21, MMP-2, MMP-9, p-JAK2 and p-STAT3 proteins. In comparison with normal ovarian epithelial cells (IOSE80), RRS1 mRNA and protein levels were increased in ovarian carcinoma cells (SKOV-3, SW626 and CAOV3) (P < 0.05). Because RRS1 levels were highest in CAOV3 cells, these cells were used for subsequent experiments. RRS1 gene expression was knocked down in CAOV3 cells, and in comparison with the negative control group, siRNA-RRS1 cells exhibited decreased proliferation in the MTT assay after 48 h and 72 h (P < 0.05). These cells also exhibited reduced migration and invasion (P < 0.05). Further, siRNA-RRS1 cells exhibited reduced expression of CyclinD1, MMP-2, MMP-9, P-JAK2 and P-STAT3 proteins (P < 0.05), while P21 protein levels were increased (P < 0.05). Silencing RRS1 expression inhibits the proliferation, migration, and invasion of ovarian carcinoma cells. This effect may be mediated by the inhibition of the STAT3 signaling pathway in these cells.

Advances in the Relationship Between Regulator of Ribosome Synthesis 1 (RRS1) and Diseases.

A regulator of ribosome synthesis 1 (RRS1) was discovered in yeast and is mainly localized in the nucleolus and endoplasmic reticulum. It regulates ribosomal protein, RNA biosynthesis, and protein secretion and is closely involved in cellular senescence, cell cycle regulation, transcription, translation, oncogenic transformation etc., Mutations in the RRS1 gene are associated with the occurrence and development of Huntington’s disease and cancer, and overexpression of RRS1 promotes tumor growth and metastasis. In this review, the structure, function, and mechanisms of RRS1 in various diseases are discussed.

Activity of nucleolar organizers in endometrial glandular and surface epithelial cells in patients with external genital endometriosis

Hypothesis/aims of study. Endometriosis is a disease characterized by proliferation of tissue that is similar in morphology and function to the endometrium, outside the uterine cavity. Thanks to the theory of J. Sampson (1927), which explains endometrioid heterotopia formation by bits of endometrial tissue migrating through the fallopian tubes during menstruation and their subsequent implantation in the pelvis, research has begun on the biological properties of eutopic endometrial cells in women with endometriosis, which is still relevant today. The present study was aimed to assess the activity of nucleolus organizers in the endometrium in women with external genital endometriosis and without it at different stages of the menstrual cycle.
 Study design, materials, and methods. Paraffin blocks of endometrial biopsy specimens were taken from 68 women with and without external genital endometriosis. The activity of nucleolar organizers was evaluated by the method of J. Crocker (1983).
 Results. The data obtained showed a significant increase in ribosomal activity in the cells of the endometrial glandular and surface epithelium in women with external genital endometriosis at the stages of late proliferation, as well as early and middle secretions. There was also a significant decrease in the activity of the nucleolar organizers of endometrial epithelial cells at the stage of late secretion in women with external genital endometriosis.
 Conclusion. The obtained differences in regulation of ribosomal synthesis in the cells of the integument and glandular epithelium of the endometrium in women with external genital endometriosis, in our opinion, can provide an increase in the total amount of epitheliocytes of the endometrium, increase their adhesive and invasive abilities, and lengthen the life cycle of cells. This contributes to the formation of endometrioid heterotopies and the development of external genital endometriosis. Changes in the activity of nucleolar organizers in the endometrium in women with external genital endometriosis may be of clinical interest for the diagnosis of this pathology.

High Prevalence of Diverse Insertion Sequences within the rRNA Operons of Mycoplasma bovis.

Data presented in this study show a high prevalence of diverse ISs within the M. bovis rrn locus resulting in intraspecies variability and diversity. Such abundance of IS elements near or within the rrn locus may offer a selective advantage to M. bovis Moreover, the fact that expression of the rrs genes as well as the number of viable cells increased in the group of strains with IS element insertion within a putative promoter -35 sequence (configuration F) in comparison to that in strains with one or two rrn operons that do not have ISs may serve as a basis for understanding the possible role of M. bovis IS elements in fundamental biological processes such as regulation of ribosome synthesis and function.

TIF-IA-Dependent Regulation of Ribosome Synthesis in Drosophila Muscle Is Required to Maintain Systemic Insulin Signaling and Larval Growth

The conserved TOR kinase signaling network links nutrient availability to cell, tissue and body growth in animals. One important growth-regulatory target of TOR signaling is ribosome biogenesis. Studies in yeast and mammalian cell culture have described how TOR controls rRNA synthesis—a limiting step in ribosome biogenesis—via the RNA Polymerase I transcription factor TIF-IA. However, the contribution of TOR-dependent ribosome synthesis to tissue and body growth in animals is less clear. Here we show in Drosophila larvae that ribosome synthesis in muscle is required non-autonomously to maintain normal body growth and development. We find that amino acid starvation and TOR inhibition lead to reduced levels of TIF-IA, and decreased rRNA synthesis in larval muscle. When we mimic this decrease in muscle ribosome synthesis using RNAi-mediated knockdown of TIF-IA, we observe delayed larval development and reduced body growth. This reduction in growth is caused by lowered systemic insulin signaling via two endocrine responses: reduced expression of Drosophila insulin-like peptides (dILPs) from the brain and increased expression of Imp-L2—a secreted factor that binds and inhibits dILP activity—from muscle. We also observed that maintaining TIF-IA levels in muscle could partially reverse the starvation-mediated suppression of systemic insulin signaling. Finally, we show that activation of TOR specifically in muscle can increase overall body size and this effect requires TIF-IA function. These data suggest that muscle ribosome synthesis functions as a nutrient-dependent checkpoint for overall body growth: in nutrient rich conditions, TOR is required to maintain levels of TIF-IA and ribosome synthesis to promote high levels of systemic insulin, but under conditions of starvation stress, reduced muscle ribosome synthesis triggers an endocrine response that limits systemic insulin signaling to restrict growth and maintain homeostasis.

Methylation of yeast ribosomal protein S2 is elevated during stationary phase growth conditions

Ribosomes, as the center of protein translation in the cell, require careful regulation via multiple pathways. While regulation of ribosomal synthesis and function has been widely studied on the transcriptional and translational “levels,” the biological roles of ribosomal post-translational modifications (PTMs) are largely not understood. Here, we explore this matter by using quantitative mass spectrometry to compare the prevalence of ribosomal methylation and acetylation for yeast in the log phase and the stationary phase of growth. We find that of the 27 modified peptides identified, two peptides experience statistically significant changes in abundance: a 1.9-fold decrease in methylation for k(Me)VSGFKDEVLETV of ribosomal protein S1B (RPS1B), and a 10-fold increase in dimethylation for r(DiMe)GGFGGR of ribosomal protein S2 (RPS2). While the biological role of RPS1B methylation has largely been unexplored, RPS2 methylation is a modification known to have a role in processing and export of ribosomal RNA. This suggests that yeast in the stationary phase increase methylation of RPS2 in order to regulate ribosomal synthesis. These results demonstrate the utility of mass spectrometry for quantifying dynamic changes in ribosomal PTMs.

Live-imaging of single stem cells within their niche reveals that a U3snoRNP component segregates asymmetrically and is required for self-renewal in Drosophila

Stem cells generate self-renewing and differentiating progeny over many rounds of asymmetric divisions. How stem cell growth rate and size are maintained over time remains unknown. We isolated mutations in a Drosophila melanogaster gene, wicked (wcd), which induce premature differentiation of germline stem cells (GSCs). Wcd is a member of the U3 snoRNP complex required for pre-ribosomal RNA maturation. This general function of Wcd contrasts with its specific requirement for GSC self-renewal. However, live imaging of GSCs within their niche revealed a pool of Wcd-forming particles that segregate asymmetrically into the GSCs on mitosis, independently of the Dpp signal sent by the niche. A fraction of Wcd also segregated asymmetrically in dividing larval neural stem cells (NSCs). In the absence of Wcd, NSCs became smaller and produced fewer neurons. Our results show that regulation of ribosome synthesis is a crucial parameter for stem cell maintenance and function.

Control of Ribosome Synthesis During the Cell Division Cycles ofE. coliandSynechococcus

The regulation of ribosome synthesis has been investigated for nearly five decades. In earlier studies, the control of rRNA synthesis in bacteria was found to be dependent on nutrient composition of the growth media or cell growth rates, and these observations led to the growth rate-dependent regulation model. Also developed were stringent control, feedback ribosome synthesis, passive regulation, and antitermination models. Current evidence indicates that upstream (UP) element, molecular effectors, ppGpp and iNTP (initiating nucleoside triphosphate), and trans-acting proteins, Fis and H-NS, play important roles in the control of rRNA synthesis in response to changing nutritional environments. The mechanisms for the ribosome feedback regulation, and growth rate-dependent controls of rRNA synthesis remain to be determined despite numerous investigations. r-protein synthesis can be controlled by translational coupling, translation repression, or premature transcription termination. In Synechococcus, a photoautotroph, ribosome synthesis occurs early in the cell cycle as programmed events under conditions that support balanced growth. Periods of r-protein synthesis occur before rRNA synthesis periods, and rRNA synthesis is stimulated by a light-activated gene regulatory protein. These observations suggest that gene regulatory proteins are involved in the coordinate regulation of ribosome assembly in Synechococcus.

The Drosophila melanogaster gene brain tumor negatively regulates cell growth and ribosomal RNA synthesis.

The regulation of ribosome synthesis is likely to play an important role in the regulation of cell growth. Previously, we have shown that the ncl-1 gene in Caenorhabditis elegans functions as an inhibitor of cell growth and ribosome synthesis. We now indicate that the Drosophila melanogaster tumor suppressor brain tumor (brat) is an inhibitor of cell growth and is a functional homolog of the C. elegans gene ncl-1. The brat gene is able to rescue the large nucleolus phenotype of ncl-1 mutants. We also show that brat mutant cells are larger, have larger nucleoli, and have more ribosomal RNA than wild-type cells. Furthermore, brat overexpressing cells contain less ribosomal RNA than control cells. These results suggest that the tumorous phenotype of brat mutants may be due to excess cell growth and ribosome synthesis.

Regulation of ribosome synthesis in Escherichia coli: Effects of temperature and dilution rate changes

The effect of temperature on the synthesis of ribosome in Escherichia coli K-12 was investigated. In continuous fermentation, the total and functioning ribosome contents decreased with increasing temperature, while the non-functioning ribosome content remained unchanged. Cells contained higher amounts of functioning ribosome at lower temperatures to compensate for the decrease in translational activity. A transient study was performed to investigate the dynamic response of the cell to changes in the dilution rate. In response to the dilution rate shift-up, the cell mass decreased until the cells produced a sufficient amount of ribosomes to support the new higher growth rate. However, the response to the dilution rate shift-down resulted in an immediate increase in cell mass. This may be due to the fact that the cell already contains enough ribosomes to support a lower growth rate corresponding to the new low dilution rate. Based on the experimental results, a mathematical model was developed to describe the cell growth at transient as well as steady states. The total ribosome content was included as a variable because it affects the growth rate of the cell.

RRS1, a conserved essential gene, encodes a novel regulatory protein required for ribosome biogenesis in Saccharomyces cerevisiae.

A secretory defect causes specific and significant transcriptional repression of both ribosomal protein and rRNA genes (K. Mizuta and J. R. Warner, Mol. Cell. Biol. 14:2493-2502, 1994), suggesting the coupling of plasma membrane and ribosome syntheses. In order to elucidate the molecular mechanism of the signaling pathway, we isolated a cold-sensitive mutant with a mutation in a gene termed RRS1 (regulator of ribosome synthesis), which appeared to be defective in the signaling pathway. The rrs1-1 mutation greatly reduced transcriptional repression of both rRNA and ribosomal protein genes that is caused by a secretory defect. RRS1 is a novel, essential gene encoding a nuclear protein of 203 amino acid residues that is conserved in eukaryotes. A conditional rrs1-null mutant was constructed by placing RRS1 under the control of the GAL1 promoter. Rrs1p depletion caused defects in processing of pre-rRNA and assembly of ribosomal subunits.

Engineering of bacterial ribosomes: replacement of all seven Escherichia coli rRNA operons by a single plasmid-encoded operon.

Since the discovery of the ribosome as the machinery essential for protein synthesis in the mid-1950s, extensive studies have been carried out with respect to ribosomal structure, function, biosynthesis, regulation. For obvious historical reasons, these studies, especially those on the structure–function relationship, have been done mostly by using Escherichi coli, leading to enormous amounts of information on E. coli ribosomes (1). One of the most impressive recent developments is the demonstration in vitro of the peptidyl transferase activity of rRNA with few or no proteins attached, confirming the suspected essential roles of rRNAs in ribosomal functions (2–4). In parallel to the in vitro studies of E. coli ribosomes, extensive genetic and physiological studies have also been carried out, identifying all of the genes for ribosomal components and giving insight into mechanisms by which E. coli regulates the synthesis of ribosomes and their molecular components (5, 6). Genetic approaches have always been essential to test the validity of conclusions derived from in vitro experiments regarding ribosome functions or regulation of ribosome synthesis. In the article by Asai et al. published in this issue of the Proceedings (7), Squires and coworkers describe their success in constructing an E. coli strain (“Δ7 prrn”) in which each of the seven chromosomal rRNA operons is inactivated by a deletion spanning the 16S and 23S RNA-coding regions, and rRNA is transcribed from a single rRNA operon carried by a multicopy plasmid. Although this success does not provide major surprises, the newly constructed rrn deletion strains provide a powerful system for mutational analysis of the structure and function of rRNAs as well as a system for studying the significance of the presence of multiple rRNA operons in bacteria.

Ncl-1 is required for the regulation of cell size and ribosomal RNA synthesis in Caenorhabditis elegans.

Regulation of ribosome synthesis is an essential aspect of growth control. Thus far, little is known about the factors that control and coordinate these processes. We show here that the Caenorhabditis elegans gene ncl-1 encodes a zinc finger protein and may be a repressor of RNA polymerase I and III transcription and an inhibitor of cell growth. Loss of function mutations in ncl-1, previously shown to result in enlarged nucleoli, result in increased rates of rRNA and 5S RNA transcription and enlarged cells. Furthermore, ncl-1 adult worms are larger, have more protein, and have twice as much rRNA as wild-type worms. Localization studies show that the level of NCL-1 protein is independently regulated in different cells of the embryo. In wild-type embryos, cells with the largest nucleoli have the lowest level of NCL-1 protein. Based on these results we propose that ncl-1 is a repressor of ribosome synthesis and cell growth.

Regulation of ribosome synthesis in yeast

Regulation of ribosome synthesis in yeast

Regulation of ribosome synthesis in yeast.

Regulation of ribosome synthesis in yeast.

Regulation of ribosome synthesis during compensatory renal hypertrophy in mice.

Ribosomal synthesis was studied at the transcriptional and translational levels to investigate the mechanisms of ribosome accretion during compensatory renal hypertrophy. As measured by in vitro transcriptional runoff comparisons 6-48 h after surgery, nuclei from the kidney remaining after contralateral nephrectomy show an increase of up to 150% in the rate of synthesis of ribosomal precursor RNA. The rate of rDNA transcription is 40-50% greater than control values as early as 6 h after nephrectomy; by 48 h, the rate returns to normal. In contrast to the stimulated transcription of rDNA and accretion of rRNA, the steady-state levels and the cytoplasmic distribution of ribosomal protein mRNAs S16 and L10 remain unchanged during induced renal growth. Thus coordinate production of adequate protein for increased assembly of ribosomes during induced renal growth appears to be accomplished by increasingly efficient translation of existing ribosomal protein mRNAs or by post-translational stabilization of ribosomal proteins. The rate of rDNA transcription may be regulated by accelerating the transcription of already functioning genes or, more likely, by recruiting transcription units that are transcriptionally inactive in the normal kidney.

Regulation of ribosome synthesis in Tetrahymena pyriformis. 2. Coordination of synthesis of ribosomal proteins and ribosomal RNA during nutritional shift-up.

The addition of nutrients to long-time-starved cells of Tetrahymena pyriformis leads to a 50-60-fold increase in the rate of synthesis of ribosomal proteins (r-proteins). This is achieved by a 6-fold increase in the relative rate of r-protein synthesis and a 8-10-fold increase in the rate of total protein synthesis. Synthesis of r-proteins constitutes one third of total cellular protein synthesis 2-4 h after refeeding and the absolute rate of r-protein synthesis is approximately three-times greater than in exponentially growing cells. The synthesis of the individual r-proteins is coordinately regulated during a nutritional shift-up, and de novo synthesized r-proteins are stable. Addition of actinomycin D prevents the increase in the rate of r-protein synthesis. The rates of synthesis of rRNA and r-protein increase in concert, implying coordinate regulation. Furthermore, a comparison of the observed accumulation of r-proteins with the predicted accumulation based on the accumulation of rRNA suggests that rRNA and r-protein are synthesized in a stoichiometrically balanced way during the entire refeeding period.

Regulation of ribosome synthesis in Tetrahymena pyriformis. 1. Coordination of synthesis of ribosomal proteins and ribosomal RNA during nutritional shift-down.

When exponentially growing cells of Tetrahymena pyriformis are transferred to a non-nutrient medium the loss of whole cell RNA, 90% of which is ribosomal RNA, exhibits biphasic kinetics, whereas whole cell protein is lost at a constant rate. The ratio RNA/protein declines during the first 5 h of starvation and then remains constant during the subsequent period of starvation. The synthesis of the majority of the ribosomal proteins is coordinately regulated during a nutritional shift-down. Exponentially growing cells devote 17% of their capacity for protein synthesis to the production of ribosomal proteins. Upon starvation this proportion is rapidly reduced 3.5-fold. In long-time-starved cells the absolute rate of ribosomal protein synthesis is only about 4.5% of that of exponentially growing cells. The synthesis of ribosomal RNA and ribosomal proteins appears tightly coupled during the transition from growth to starvation. In long-time-starved cells the synthesis of ribosomal RNA and ribosomal proteins are stoichiometrically balanced with no significant degradation of de novo synthesized ribosomal proteins.