Showing papers on "Ribosomal protein published in 1991"
TL;DR: Self peptides derive from abundant cytosolic or nuclear proteins, such as histone, ribosomal proteins, and members of the 90K heat-shock protein family, and match to protein sequences in a database search.
Abstract: A pool of endogenous peptides bound to the human class I MHC molecule, HLA-B27, has been isolated. Microsequence analysis of the pool and of 11 HPLC-purified peptides provides information on the binding specificity of the HLA-B27 molecule. The peptides all seem to be nonamers, seven of which match to protein sequences in a database search. These self peptides derive from abundant cytosolic or nuclear proteins, such as histone, ribosomal proteins, and members of the 90K heat-shock protein family.
897 citations
430 citations
TL;DR: The number of small subunit rRNA sequences is now great enough that the three domains Archaea, Bacteria and Eucarya can be reliably defined in terms of their sequence "signatures", and the three can be recognized by a variety of nonhomologous rRNA characters.
325 citations
TL;DR: It is demonstrated that Watson‐Crick interactions between these nucleotides are essential for ribosomal function, and certain mild perturbations of the structure generate resistance to streptomycin, an antibiotic known to interfere with the decoding process.
Abstract: Several lines of evidence indicate that the universally conserved 530 loop of 16S ribosomal RNA plays a crucial role in translation, related to the binding of tRNA to the ribosomal A site. Based upon limited phylogenetic sequence variation, Woese and Gutell (1989) have proposed that residues 524-526 in the 530 hairpin loop are base paired with residues 505-507 in an adjoining bulge loop, suggesting that this region of 16S rRNA folds into a pseudoknot structure. Here, we demonstrate that Watson-Crick interactions between these nucleotides are essential for ribosomal function. Moreover, we find that certain mild perturbations of the structure, for example, creation of G-U wobble pairs, generate resistance to streptomycin, an antibiotic known to interfere with the decoding process. Chemical probing of mutant ribosomes from streptomycin-resistant cells shows that the mutant ribosomes have a reduced affinity for streptomycin, even though streptomycin is thought to interact with a site on the 30S subunit that is distinct from the 530 region. Data from earlier in vitro assembly studies suggest that the pseudoknot structure is stabilized by ribosomal protein S12, mutations in which have long been known to confer streptomycin resistance and dependence.
283 citations
TL;DR: It is shown that binding of the ssb mRNA to 30S ribosomes is S1-dependent and the oligo(U)-sequence preceding the SD domain was found to be the target for S1.
Abstract: Ribosomal protein S1 is known to play an important role in translational initiation, being directly involved in recognition and binding of mRNAs by 30S ribosomal particles. Using a specially developed procedure based on efficient crosslinking of S1 to mRNA induced by UV irradiation, we have identified S1 binding sites on several phage RNAs in preinitiation complexes. Targets for S1 on Q beta and fr RNAs are localized upstream from the coat protein gene and contain oligo(U)-sequences. In the case of Q beta RNA, this S1 binding site overlaps the S-site for Q beta replicase and the site for S1 binding within a binary complex. It is reasonable that similar U-rich sequences represent S1 binding sites on bacterial mRNAs. To test this idea we have used E. coli ssb mRNA prepared in vitro with the T7 promoter/RNA polymerase system. By the methods of toeprinting, enzymatic footprinting, and UV crosslinking we have shown that binding of the ssb mRNA to 30S ribosomes is S1-dependent. The oligo(U)-sequence preceding the SD domain was found to be the target for S1. We propose that S1 binding sites, represented by pyrimidine-rich sequences upstream from the SD region, serve as determinants involved in recognition of mRNA by the ribosome.
278 citations
245 citations
TL;DR: The results suggest that there is increased synthesis of ribosomes in colorectal tumors and that this increase is an early event in colon neoplasia.
Abstract: We have isolated a cDNA clone encoding the human S3 ribosomal protein from a normal human colon cDNA library. The clone was identified as one of many that detected genes whose level of expression was increased in adenocarcinoma of the colon relative to normal colonic mucosa. Increased levels of the S3 transcript were present in the tumors of all eight patients examined. Moreover, the S3 mRNA was also more abundant in 7 of 10 adenomatous polyps, the presumed precursor of carcinoma. Additional studies demonstrated that increased levels of mRNAs encoding several other ribosomal proteins, including S6, S8, S12, L5, and P0, were present in colorectal tumors and polyps. These results suggest that there is increased synthesis of ribosomes in colorectal tumors and that this increase is an early event in colon neoplasia.
221 citations
TL;DR: The amount of information collected on the structure and function of ribosomal genes in yeast surpasses that available for any other eukaryote and has provided important insights into the regulatory mechanisms controlling the expression of these genes.
Abstract: Publisher Summary This chapter focuses on the concept of ribosome biogenesis in yeast. The formation of functional ribosomes is a highly complex phenomenon requiring the interplay of a large number of molecular processes. Ribosomes contain, depending on their origin, some 60–80 different components, proteins, and RNA molecules, most in a single copy per ribosome. Because normally growing cells generally contain no free pools of these ribosomal components, the expression of the numerous ribosomal genes must be subject to tight coordinate control to ensure the production of equimolar amounts of the various rRNA and ribosomal-protein (r-protein) constituents. Because of its accessibility to genetic and physiological manipulation, the yeast— Saccharomyces cereuisiae— has become one of the most popular organisms for studying the questions raised by the coordinate control of ribosome biogenesis in eukaryotes. The genes for the various yeast rRNAs and those for about 40 of the yeast r-proteins have been cloned and subjected to studies. As a result, the amount of information collected on the structure and function of ribosomal genes in yeast surpasses that available for any other eukaryote. This information has provided important insights into the regulatory mechanisms controlling the expression of these genes. In addition, progress has been made in developing systems that provide access to the hitherto largely unexplored field of eukaryotic ribosome assembly, including the mechanism of rRNA processing.
217 citations
TL;DR: The human immunodeficiency virus type 1 (HIV) Rev protein is thought to be involved in the export of unspliced or singly spliced viral mRNAs from the nucleus to the cytoplasm through a sequence-specific interaction with a cis-acting RNA element, the Rev response element (RRE), present in these intron-containing RNAs.
Abstract: The human immunodeficiency virus type 1 (HIV) Rev protein is thought to be involved in the export of unspliced or singly spliced viral mRNAs from the nucleus to the cytoplasm. This function is mediated by a sequence-specific interaction with a cis-acting RNA element, the Rev response element (RRE), present in these intron-containing RNAs. To identify possible host proteins involved in Rev function, we fractionated nuclear cell extracts with a Rev affinity column. A single, tightly associated Rev-binding protein was identified; this protein is the mammalian nucleolar protein B23. The interaction between HIV Rev and B23 is very specific, as it was observed in complex cell extracts. The complex is also very stable toward dissociation by high salt concentrations. Despite the stability of the Rev-B23 protein complex, the addition of RRE, but not control RNA, led to the displacement of B23 and the formation of a specific Rev-RRE complex. The mammalian nucleolar protein B23 or its amphibian counterpart No38 is believed to function as a shuttle receptor for the nuclear import of ribosomal proteins. B23 may also serve as a shuttle for the import of HIV Rev from the cytoplasm into the nucleus or nucleolus to allow further rounds of export of RRE-containing viral RNAs.
205 citations
TL;DR: It is found that inhibiting 40S-60S subunit joining by deleting one copy (RPL16B) of the duplicated gene encoding the 60S ribosomal protein L16 qualitatively mimics the phenotype of gcd2 mutations in causing derepression of GCN4 expression under nonstarvation conditions, indicating that lowering the concentration of 60S subunits and reducing GCD2 function affect translation initiation at GCN 4 in different ways.
Abstract: The GCD2 protein is a translational repressor of GCN4, the transcriptional activator of multiple amino acid biosynthetic genes in Saccharomyces cerevisiae. We present evidence that GCD2 has a general function in the initiation of protein synthesis in addition to its gene-specific role in translational control of GCN4 expression. Two temperature-sensitive lethal gcd2 mutations result in sensitivity to inhibitors of protein synthesis at the permissive temperature, and the gcd2-503 mutation leads to reduced incorporation of labeled leucine into total protein following a shift to the restrictive temperature of 36 degrees C. The gcd2-503 mutation also results in polysome runoff, accumulation of inactive 80S ribosomal couples, and accumulation of at least one of the subunits of the general translation initiation factor 2 (eIF-2 alpha) in 43S-48S particles following a shift to the restrictive temperature. The gcd2-502 mutation causes accumulation of 40S subunits in polysomes, known as halfmers, that are indicative of reduced 40S-60S subunit joining at the initiation codon. These phenotypes suggest that GCD2 functions in the translation initiation pathway at a step following the binding of eIF-2.GTP.Met-tRNA(iMet) to 40S ribosomal subunits. consistent with this hypothesis, we found that inhibiting 40S-60S subunit joining by deleting one copy (RPL16B) of the duplicated gene encoding the 60S ribosomal protein L16 qualitatively mimics the phenotype of gcd2 mutations in causing derepression of GCN4 expression under nonstarvation conditions. However, deletion of RPL16B also prevents efficient derepression of GCN4 under starvation conditions, indicating that lowering the concentration of 60S subunits and reducing GCD2 function affect translation initiation at GCN4 in different ways. This distinction is in accord with a recently proposed model for GCN4 translational control in which ribosomal reinitiation at short upstream open reading frames in the leader of GCN4 mRNA is suppressed under amino acid starvation conditions to allow for increased reinitiation at the GCN4 start codon.
172 citations
TL;DR: In this paper, the authors used the antimetabolite 3-amino-1,2,4-triazole to cause stringent control in the yeast Saccharomyces cerevisiae.
Abstract: An amino acid limitation in bacteria elicits a global response, called stringent control, that leads to reduced synthesis of rRNA and ribosomal proteins and increased expression of amino acid biosynthetic operons. We have used the antimetabolite 3-amino-1,2,4-triazole to cause histidine limitation as a means to elicit the stringent response in the yeast Saccharomyces cerevisiae. Fusions of the yeast ribosomal protein genes RPL16A, CRY1, RPS16A, and RPL25 with the Escherichia coli lacZ gene were used to show that the expression of these genes is reduced by a factor of 2 to 5 during histidine-limited exponential growth and that this regulation occurs at the level of transcription. Stringent regulation of the four yeast ribosomal protein genes was shown to be associated with a nucleotide sequence, known as the UASrpg (upstream activating sequence for ribosomal protein genes), that binds the transcriptional regulatory protein RAP1. The RAP1 binding sites also appeared to mediate the greater ribosomal protein gene expression observed in cells growing exponentially than in cells in stationary phase. Although expression of the ribosomal protein genes was reduced in response to histidine limitation, the level of RAP1 DNA-binding activity in cell extracts was unaffected. Yeast strains bearing a mutation in any one of the genes GCN1 to GCN4 are defective in derepression of amino acid biosynthetic genes in 10 different pathways under conditions of histidine limitation. These Gcn- mutants showed wild-type regulation of ribosomal protein gene expression, which suggests that separate regulatory pathways exist in S. cerevisiae for the derepression of amino acid biosynthetic genes and the repression of ribosomal protein genes in response to amino acid starvation.
TL;DR: The topography of the rRNA regions responsible for protein synthesis can be described and a complex distribution of higher mass density is recognized, which is attributed to ribosomal RNA.
Abstract: A reconstruction, at 40 A, of the Escherichia coli ribosome imaged by cryo-electron microscopy, obtained from 303 projections by a single-particle method of reconstruction, shows the two subunits with unprecedented clarity. In the interior of the subunits, a complex distribution of higher mass density is recognized, which is attributed to ribosomal RNA. The masses corresponding to the 16S and 23S components are linked in the region of the platform of the small subunit. Thus the topography of the rRNA regions responsible for protein synthesis can be described.
TL;DR: GCN2 interacts with ribosomes during the translation initiation cycle, suggesting that ribosome association by GCN2 is important for its access to substrates in the translational machinery or for detecting uncharged tRNA in amino acid-starved cells.
Abstract: The GCN4 gene of the yeast Saccharomyces cerevisiae encodes a transcriptional activator of amino acid biosynthetic genes that is regulated at the translational level according to the availability of amino acids. GCN2 is a protein kinase required for increased translation of GCN4 mRNA in amino acid-starved cells. Centrifugation of cell extracts in sucrose gradients indicated that GCN2 comigrates with ribosomal subunits and polysomes. The fraction of GCN2 cosedimenting with polysomes was reduced under conditions in which polysomes were dissociated, suggesting that GCN2 is physically bound to these structures. When the association of 40S and 60S subunits was prevented by omitting Mg2+ from the gradient, almost all of the GCN2 comigrated with 60S ribosomal subunits, and it remained bound to these particles during gel electrophoresis under nondenaturing conditions. GCN2 could be dissociated from 60S subunits by 0.5 M KCl, suggesting that it is loosely associated with ribosomes rather than being an integral ribosomal protein. Accumulation of GCN2 on free 43S-48S particles and 60S subunits occurred during polysome runoff in vitro and under conditions of reduced growth rate in vivo. These observations, plus the fact that GCN2 shows preferential association with free ribosomal subunits during exponential growth, suggest that GCN2 interacts with ribosomes during the translation initiation cycle. The extreme carboxyl-terminal segment of GCN2 is essential for its interaction with ribosomes. These sequences are also required for the ability of GCN2 to stimulate GCN4 translation in vivo, leading us to propose that ribosome association by GCN2 is important for its access to substrates in the translational machinery or for detecting uncharged tRNA in amino acid-starved cells.
TL;DR: The results suggest that the loop has a complex structure, affected by ribosomal proteins, and this bears on the function in protein synthesis of the alpha-sarcin/ricin rRNA domain.
TL;DR: It is suggested that the DeaD protein plays a hitherto unknown role in translation in E. coli.
Abstract: We have cloned and sequenced a new gene from Escherichia coli which encodes a 64-kDa protein. The inferred amino acid sequence of the protein shows remarkable similarity to eIF4A, a murine translation initiation factor that has an ATP-dependent RNA helicase activity and is a founding member of the D-E-A-D family of proteins (characterized by a conserved Asp-Glu-Ala-Asp motif). Our new gene, called deaD, was cloned as a gene dosage-dependent suppressor of temperature-sensitive mutations in rpsB, the gene encoding ribosomal protein S2. We suggest that the DeaD protein plays a hitherto unknown role in translation in E. coli.
TL;DR: Northern blot analysis with a tail-specific probe indicated that the previously identified UbA mRNA species most likely represents comigrating transcripts of the 52 amino acid tail (UbA52) and 80 amino acids tail ( UbA80) ubiquitin fusion genes.
Abstract: Complementary DNA clones encoding ubiquitin fused to a 52 amino acid tail protein were isolated from human placental and adrenal gland cDNA libraries. The deduced human 52 amino acid tail protein is very similar to the homologous protein from other species, including the conservation of the putative metal-binding, nucleic acid-binding domain observed in these proteins. Northern blot analysis with a tail-specific probe indicated that the previously identified UbA mRNA species most likely represents comigrating transcripts of the 52 amino acid tail (UbA52) and 80 amino acid tail (UbA80) ubiquitin fusion genes. The UbA52 gene was isolated from a human genomic library and consists of five exons distributed over 3400 base pairs. One intron is in the 5' non-coding region, two interrupt the single ubiquitin coding unit, and the fourth intron is within the tail coding region. Several members of the Alu family of repetitive DNA are associated with the gene. The UbA52 promoter has several features in common with mammalian ribosomal protein genes, including its location in a CpG-rich island, initiation of transcription within a polypyrimidine tract, the lack of a consensus TATA motif, and the presence of Sp1 binding sites, observations that are consistent with the recent identification of the ubiquitin-free tail proteins as ribosomal proteins. Thus, in spite of its unusual feature of being translationally fused to ubiquitin, the 52 amino acid tail ribosomal protein is expressed from a structurally typical ribosomal protein gene.
TL;DR: The rapid degradation of the processed mRNA in an rne+ strain, compared to the slow degradation ofThe transcript that accumulates in a rne- strain, suggests that RNase E initiates the decay of the rpsO message by removing the stabilizing stem-loop at the 3' end of the RNA.
TL;DR: The rat P-proteins have a near identical sequence of amino acids at their carboxyl termini and are related to analogous proteins in other eukaryotic species and a proposal is made for a uniform nomenclature for rat and yeast ribosomal proteins.
TL;DR: The presence of severe stunting and striping in NCS3 plants correlates absolutely with the molecular changes described here and indicates that one or both of these reading frames are translated to functional ribosomal proteins in normal maize mitochondria.
Abstract: A deletion eliminating part of a transcribed region of mitochondrial DNA (mtDNA) has been found in the maize nonchromosomal stripe 3 (NCS3) mutant. This results in the specific loss of a set of three mitochondrial RNAs consisting, in normal plants, of a 4.9 kb transcript, its 1.8 kb intron and the resulting processed mRNA of approximately 2.9 kb. In the NCS3 mitochondrial genome the DNA encoding the putative promoter and 5' end of the affected RNAs is missing. This transcribed region of normal maize mtDNA has been sequenced and the intron splice junction has been determined. The 2.9 kb processed mRNA carries two overlapping open reading frames (ORFs) with predicted amino acid sequences that show similarity to two Escherichia coli ribosomal proteins, S3 (rps3) and L16 (rpl16). The presence of severe stunting and striping in NCS3 plants correlates absolutely with the molecular changes described here. This fact and the impaired ability for mitochondrial protein synthesis by NCS3 plants indicate that one or both of these reading frames are translated to functional ribosomal proteins in normal maize mitochondria.
TL;DR: Taken together, the data show that the fractionated extract described here reproduces steps in the degradation of some mRNAs which occur in living cells.
Abstract: Endonucleolytic cleavage is believed to initiate the degradation of most bacterial mRNAs, but with several exceptions, the enzymes responsible have yet to be identified. Crude (S-30) or partially fractionated extracts of Escherichia coli strains with reduced exonuclease activities catalyze the cleavage of a 372-residue RNA substrate containing the sequences coding for ribosomal protein S20 to yield a number of discrete products. The major product of 147 residues is obtained in 60 to 70% yield, is coterminal with the 3' end of the substrate, and is identical to an mRNA fragment previously characterized in vivo (G. A. Mackie, J. Bacteriol. 171:4112-4120, 1989). A number of other products of 150 to 340 residues are also formed, and the cleavage sites, typically N decreases AU sequences, have been identified in the S20 mRNA substrate by Northern (RNA) blotting and primer extension. All cleavages required a native rather than a denatured RNA substrate. The rate of cutting of the S20 mRNA substrate at the site yielding the prominent 147-residue product appears to be independent of cleavages at other sites. In addition, the activity of the putative endonuclease(s) depends strongly, both in vivo and in vitro, on the product of the ams gene, which is known to influence mRNA lifetimes in vivo. Taken together, the data show that the fractionated extract described here reproduces steps in the degradation of some mRNAs which occur in living cells.
TL;DR: The activity of 80S ribosomes in poly(U)-directed synthesis of polyphenylalanine was tested in a polysome-free protein-synthesizing system from rabbit reticulocytes and activity was equal to 80%.
TL;DR: Recent findings indicate that TUF/RAP also activates other gene families involved in cellular growth rate and binds to the mating-type silencer and telomeres in yeast.
Abstract: The rate of ribosome formation in yeast is precisely adjusted to the physiological demands of the cell. During all growth conditions a balance is maintained in the production of all ribosomal constituents. Coordinate expression of the ribosomal protein (rp) genes is primarily accomplished at the transcriptional level. Transcription activation of the majority of the rp-genes is mediated through common upstream activating sequences, so-called RPG boxes, which occur usually in a tandem at a distance of 200-500 bp from the start codon. These RPG-boxes represent binding sites for a transcriptional activator, called TUF or RAP. The concentration of TUF parallels the cellular growth rate and evidence exists that the response of rp-genes upon nutritional changes is mediated by this factor. Recent findings indicate that TUF/RAP also activates other gene families involved in cellular growth rate. Furthermore, this multifunctional protein also binds to the mating-type silencer and telomeres in yeast.
TL;DR: The proposed tertiary model is consistent with the localization of the ribosomal protein binding sites and possesses strong analogy with the model proposed for Xenopus laevis 5 S rRNA, indicating that the Y-shape model can be generalized to all5 S rRNAs.
TL;DR: The role of the ribosome proteins and ribosomal functions are discussed and the extent of rRNA found to participate in these activities are described and three-dimensional structural information is used in the application of this technique.
Abstract: Publisher Summary This chapter discusses the role of the ribosomal proteins and ribosomal functions and describes the extent of rRNA found to participate in these activities. Several of the proteins are also known to be closely associated with different functions. The ribosome is the site of protein synthesis in all organisms. It is a complex organelle composed of a few RNA molecules and a complement of a large number of relatively small proteins. In the analysis of macromolecular functions there is a need to identify the groups involved and to visualize the structures responsible for a certain function. One important method for the exploration of structural and functional relationships is in vitro mutagenesis. Three-dimensional structural information is used in the application of this technique. Protein synthesis is performed in three separate phases: initiation, elongation, and termination. The main events during these three phases for bacterial protein synthesis, which serve as a model for protein synthesis, are summarized in the chapter.
TL;DR: Exogenous CK II and a ribosome-bound, CK II-like enzyme phosphorylate the ribosomal P proteins in vitro and localize the target site for phosphorylation to the COOH terminus, demonstrating that the P proteins are in vivo substrates of CK II.
TL;DR: Comparative sequence analysis of the rRNA gene and the proposed secondary structure ofThe rRNA suggest that it is of organellar origin, and while some characteristics of the small subunit r RNA gene are similar to mitochondrial sequences, others are more like those of plastids.
TL;DR: This review presents an overview of the mechanisms modulating the production of ribosomal precursor molecules and the rate of Ribosome biogenesis in various biological systems.
Abstract: Ribosome biogenesis in eucaryotic cells involves the coordinated synthesis of four rRNA species, transcribed by RNA polymerase I (18S, 28S, 5.8S) and RNA polymerase III (5S), and approximately 80 ribosomal proteins translated from mRNAs synthesized by RNA polymerase II. Assembly of the ribosomal subunits in the nucleolus, the site of 45S rRNA precursor gene transcription, requires the movement of 5S rRNA and ribosomal proteins from the nucleoplasm and cytoplasm, respectively, to this structure. To integrate these events and ensure the balanced production of individual ribosomal components, different strategies have been developed by eucaryotic organisms in response to a variety of physiological changes. This review presents an overview of the mechanisms modulating the production of ribosomal precursor molecules and the rate of ribosome biogenesis in various biological systems.
TL;DR: It has been found that, while IgGs specific for L44 and L45 do not inhibit the ribosome activity, the anti-L44' effectively blocks the polymerizing activity of the particles.
Abstract: In order to characterize the acidic ribosomal proteins immunologically and functionally, a battery of monoclonal antibodies specific for L44, L44' and L45, the three acidic proteins detected in Saccharomyces cerevisiae, were obtained. Eight monoclonal antibodies were obtained specific for L45, three for L44' and one for L44. In addition, two mAbs recognizing only the phosphorylated forms of the three proteins were obtained. The specific immunogenic determinants are located in the middle region of the protein structure and are differently exposed in the ribosomal surface. The common determinants are present in the carboxyl end of the three proteins. An estimation of the acidic proteins by ELISA indicated that, in contrast to L44 and L45, L44' is practically absent from the cell supernatant; this suggests that protein L44' does not intervene in the exchange that has been shown to take place between the acidic proteins in the ribosome and in the cytoplasmic pool. It has also been found that, while IgGs specific for L44 and L45 do not inhibit the ribosome activity, the anti-L44' effectively blocks the polymerizing activity of the particles. These results show for the first time that the different eukaryotic acidic ribosomal proteins play a different functional role.
TL;DR: Temperature-sensitive mutants defective in 60S ribosomal subunit protein L16 of Saccharomyces cerevisiae were isolated through hydroxylamine mutagenesis of the RPL16B gene and plasmid shuffling and it is proposed that mutants containing the rpl16b alleles are defective for 60S subunit assembly rather than function.
Abstract: Temperature-sensitive mutants defective in 60S ribosomal subunit protein L16 of Saccharomyces cerevisiae were isolated through hydroxylamine mutagenesis of the RPL16B gene and plasmid shuffling. Two heat-sensitive and two cold-sensitive isolates were characterized. The growth of the four mutants is inhibited at their restrictive temperatures. However, many of the cells remain viable if returned to their permissive temperatures. All of the mutants are deficient in 60S ribosomal subunits and therefore accumulate translational preinitiation complexes. Three of the mutants exhibit a shortage of mature 25S rRNA, and one accumulates rRNA precursors. The accumulation of rRNA precursors suggests that ribosome assembly may be slowed in this mutant. These phenotypes lead us to propose that mutants containing the rpl16b alleles are defective for 60S subunit assembly rather than function. In the mutant carrying the rpl16b-1 allele, ribosomes initiate translation at the noncanonical codon AUA, at least on the rpl16b-1 mRNA, bringing to light a possible connection between the rate and the fidelity of translation initiation.
TL;DR: This chapter reviews the recent progress in studies of the biogenesis and structure of yeast ribosomes, emphasizing results derived from experiments using classical and molecular genetics.
Abstract: Publisher Summary This chapter reviews the recent progress in studies of the biogenesis and structure of yeast ribosomes, emphasizing results derived from experiments using classical and molecular genetics. Studies of the biosynthesis of the yeast ribosome offer an opportunity to investigate the coordinate expression of a moderately large set of genes that respond to the growth rate of the cell. To understand ribosome biosynthesis, one must concern the mechanisms responsible for the accumulation of ribosomal proteins in balance with each other and with rRNAs. The chapter also focuses on the structure and expression of ribosomal protein genes. The mechanisms of rRNA processing and ribosome assembly and the role of nucleolar molecules in these processes are only at their stage to be explored in eukaryotes. The signals that coordinate the transcription of these genes with all the three RNA polymerases have not been identified. By analogy to studies of mRNA processing, it should be possible to make effective use of rRNA-processing mutants or nucleolar protein or RNA mutants—in concern with a cell-free system—to define the pathway of processing in more detail and to determine the functions of trans-acting factors in this pathway.