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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Modifications of ribosomes have been investigated in human epidermoid carcinoma-2 cells at different stages of herpes simplex virus type 1 infection. Very early in infection, there is an increase in ribosomal protein S6 phosphorylation even in the absence of serum. The same result is obtained in the presence of actinomycin D. At early infection time, ribosomal proteins S2, S3a and Sa are newly phosphorylated. At early and early-late times, three phosphorylated non-ribosomal proteins (v1, v2 and v3) are differently associated temporally to ribosomes. Analyses of proteins extracted from 40S subunits, 80S ribosomes and polysomes show that v1 and v2 are distributed differently among the different ribosomal populations. S6 phosphopeptides were found to be identical after serum stimulation and after viral infection. In every case phosphoserine and phosphothreonine were identified in S6. Only phosphoserine was found in other phosphorylated proteins. Our results indicate that herpes simplex virus type 1 is able to modify pre-existing ribosomes: (i) by stimulating a pre-existing kinase for S6 phosphorylation even in the absence of serum and of viral genome expression; (ii) by inducing new specific kinase activity(ies); and (iii) by association of new, phosphorylated proteins to ribosomes. These ribosomal modifications are correlated with changes in protein synthesis, as shown by two-dimensional electrophoretic analyses of newly synthesized 35S-labelled proteins.
Mol Gen Genet 1990 Feb
PMID:Ribosome and protein synthesis modifications after infection of human epidermoid carcinoma cells with herpes simplex virus type 1. 216 50

In the yeast Saccharomyces cerevisiae, L30 is one of many ribosomal proteins that is encoded by two functional genes. We have cloned and sequenced RPL30B, which shows strong homology to RPL30A. Use of mRNA as a template for a polymerase chain reaction demonstrated that RPL30B contains an intron in its 5' untranslated region. This intron has an unusual 5' splice site, C/GUAUGU. The genomic copies of RPL30A and RPL30B were disrupted by homologous recombination. Growth rates, primer extension, and two-dimensional ribosomal protein analyses of these disruption mutants suggested that RPL30A is responsible for the majority of L30 production. Surprisingly, meiosis of a diploid strain carrying one disrupted RPL30A and one disrupted RPL30B yielded four viable spores. Ribosomes from haploid cells carrying both disrupted genes had no detectable L30, yet such cells grew with a doubling time only 30% longer than that of wild-type cells. Furthermore, depletion of L30 did not alter the ratio of 60S to 40S ribosomal subunits, suggesting that there is no serious effect on the assembly of 60S subunits. Polysome profiles, however, suggest that the absence of L30 leads to the formation of stalled translation initiation complexes.
Mol Cell Biol 1990 Oct
PMID:Ribosomal protein L30 is dispensable in the yeast Saccharomyces cerevisiae. 220 9

We have cloned the genes for small acidic ribosomal proteins (A-proteins) of the fission yeast Schizosaccharomyces pombe. S. pombe contains four transcribed genes for small A-proteins per haploid genome, as is the case for Saccharomyces cerevisiae. In contrast, multicellular eucaryotes contain two transcribed genes per haploid genome. The four proteins of S. pombe, besides sharing a high overall similarity, form two couples of nearly identical sequences. Their corresponding genes have a very conserved structure and are transcribed to a similar level. Surprisingly, of each couple of genes coding for nearly identical proteins, one is essential for cell growth, whereas the other is not. We suggest that the unequal importance of the four small A-proteins for cell survival is related to their physical organization in 60S ribosomal subunits.
Mol Cell Biol 1990 May
PMID:A gene family for acidic ribosomal proteins in Schizosaccharomyces pombe: two essential and two nonessential genes. 232 55

Seven ribosomal proteins have been localized by means of immunoelectron microscopy on the surface of the 40S ribosomal subunit from rat liver using monospecific antibodies. The location of ribosomal proteins S13/16, S19, and S24 is described for the first time, and that of ribosomal proteins S2, S3, S3a, and S7, which has been published previously on the basis of experiments performed with less well characterized antibody preparations [Lutsch et al., Mol. Gen. Genet. 176, 281-291 (1979) and Biomed. Biochim. Acta 42, 705-723 (1983)], is corrected in this paper. The results are discussed with respect to the involvement of these proteins in functional sites of the 40S ribosomal subunit.
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PMID:Immunoelectron microscopic studies on the location of ribosomal proteins on the surface of the 40S ribosomal subunit from rat liver. 232 35

A cDNA expression vector encoding Drosophila ribosomal protein S14 was transfected into cultured Chinese hamster ovary (CHO) cells that harbor a recessive RPS14 emetine resistance mutation. Transformants synthesized the insect mRNA and polypeptide and consequently displayed an emetine-sensitive phenotype. These observations indicate that the insect protein was accurately expressed and correctly assembled into functional mammalian 40S ribosomal subunits.
Mol Cell Biol 1990 Sep
PMID:A Drosophila ribosomal protein functions in mammalian cells. 238 16

We have investigated the role of a novel temperature-sensitive splicing mutation, prp18. We had previously demonstrated that an accumulation of the lariat intermediate of splicing occurred at the restrictive temperature in vivo. We have now used the yeast in vitro splicing system to show that extracts from this mutant strain are heat labile for the second reaction of splicing. The heat inactivation of prp18 extracts results from loss of activity of an exchangeable component. Inactivated prp18 extracts are complemented by heat-inactivated extracts from other mutants or by fractions from wild-type extracts. In heat-inactivated prp18 extracts, 40S splicing complexes containing lariat intermediate and exon 1 can assemble. The intermediates in this 40S complex can be chased to products by complementing extracts in the presence of ATP. Both complementation of extracts and chasing of the isolated prp18 spliceosomes takes place with micrococcal nuclease-treated extracts. Furthermore, the complementation profile with fractions of wild-type extracts indicates that the splicing defect results from a mutation in a previously designated factor required for the second step of splicing. The isolation of this mutant as temperature-sensitive lethal has also facilitated cloning of the wild-type allele by complementation.
Mol Cell Biol 1990 Jan
PMID:PRP18, a protein required for the second reaction in pre-mRNA splicing. 240 39

Modification of 60S ribosomal subunits from rat liver with dimethylmaleic anhydride (60 mumols/ml) is accompanied by release of 35% of the protein. The acidic ribosomal proteins, as well as 9 basic proteins, are selectively liberated from the ribosomal subunits. Reconstitution of the protein-deficient particles with the corresponding split proteins is accompanied by substantial recovery of the original polyphenylalanine synthetic activity. The described reconstitution procedure can be used to investigate the roles played by the released proteins and the functional similarities of proteins from different sources. Hybrid reconstitution of residual ribosomal particles from rat liver or yeast with the corresponding heterologous split proteins produces subunits which have incorporated heterologous proteins but are inactive in polyphenylalanine synthesis.
Mol Cell Biochem 1990 Feb 09
PMID:Reconstitution of rat liver 60S ribosomal subunits following disassembly by dimethylmaleic anhydride. 240 40

A number of closely related post-transcriptional facets of RNA metabolism show nuclear compartmentation, including capping, methylation, splicing reactions, and packaging in ribonucleoprotein particles (RNP). These nuclear 'processing' events are followed by the translocation of the finished product across the nuclear envelope. Due to the inherent complexity of these interrelated events, in vitro systems have been designed to examine the processes separately, particularly so with regard to translocation. A few studies have utilized nuclear transplantation/microinjection techniques and specialized systems to show that RNA transport occurs as a regulated phenomenon. While isolated nuclei swell in aqueous media and dramatic loss of nuclear protein is associated with this swelling, loss of RNA is not substantial, and most studies on RNA translocation have employed isolated nuclei. The quantity of RNA transported from isolated nuclei is related to hydrolysis of high-energy phosphate bonds in nucleotide additives. The RNA is released predominantly in RNP: messenger-like RNA is released in RNP which have buoyant density and polypeptide composition similar to cytoplasmic messenger RNP, but which have distinctly different composition from those in heterogeneous nuclear RNP. Mature 18 and 28S ribosomal RNA is released in 40 and 60S RNP which represent mature ribosomal subunits. RNA transport proceeds with characteristics of an energy-requiring process, and proceeds independently of the presence or state of fluidity of nuclear membranes. The energy for transport appears to be utilized by a nucleoside triphosphatase (NTPase) which is distributed mainly within heterochromatin at the peripheral lamina. Photoaffinity labeling has identified the pertinent NTPase as a 46 kD polypeptide which is associated with nuclear envelope and matrix preparations. The NTPase does not appear to be modulated via direct phosphorylation or to reflect kinase-phosphatase activities. A large number of additives (including RNA and insulin) produce parallel effects upon RNA transport and nuclear envelope NTPase, strengthening the correlative relationship between these activities. Of particular interest has been the finding that carcinogens induce specific, long-lasting increases in nuclear envelope (and matrix) NTPase; this derangement may underlie the alterations in RNA transport associated with cancer and carcinogenesis.(ABSTRACT TRUNCATED AT 400 WORDS)
Mol Cell Biochem 1985 Jul
PMID:Nucleocytoplasmic RNA transport. 241 44

The assembly of mammalian pre-mRNAs into large 50S to 60S complexes, or spliceosomes, containing small nuclear ribonucleoproteins (snRNPs) leads to the production of splicing intermediates, 5' exon and lariat-3' exon, and the subsequent production of spliced products. Influenza virus NS1 mRNA, which encodes a virus-specific protein, is spliced in infected cells to form another viral mRNA (the NS2 mRNA), such that the ratio of unspliced to spliced mRNA is 10 to 1. NS1 mRNA was not detectably spliced in vitro with nuclear extracts from uninfected HeLa cells. Surprisingly, despite the almost total absence of splicing intermediates in the in vitro reaction, NS1 mRNA very efficiently formed ATP-dependent 55S complexes. The formation of 55S complexes with NS1 mRNA was compared with that obtained with an adenovirus pre-mRNA (pKT1 transcript) by using partially purified splicing fractions that restricted the splicing of the pKT1 transcript to the production of splicing intermediates. At RNA precursor levels that were considerably below saturation, approximately 10-fold more of the input NS1 mRNA than of the input pKT1 transcript formed 55S complexes at all time points examined. The pKT1 55S complexes contained splicing intermediates, whereas the NS1 55S complexes contained only precursor NS1 mRNA. Biotin-avidin affinity chromatography showed that the 55S complexes formed with either NS1 mRNA or the pKT1 transcript contained the U1, U2, U4, U5, and U6 snRNPs. Consequently, the formation of 55S complexes containing these five snRNPs was not sufficient for the catalysis of the first step of splicing, indicating that some additional step(s) needs to occur subsequent to this binding. These results indicate that the 5' splice site, 3' and branch point of NS1 and mRNA were capable of interacting with the five snRNPs to form 55S complexes, but apparently some other sequence element(s) in NS1 mRNA blocked the resolution of the 55S complexes that leads to the catalysis of splicing. On the basis of our results, we suggest mechanisms by which the splicing of NS1 is controlled in infected cells.
Mol Cell Biol 1989 Jan
PMID:A block in mammalian splicing occurring after formation of large complexes containing U1, U2, U4, U5, and U6 small nuclear ribonucleoproteins. 252 88

To develop a system for the analysis of eucaryotic ribosomal DNA (rDNA) mutations, we cloned a complete, transcriptionally active rDNA unit from the yeast Saccharomyces cerevisiae on a centromere-containing yeast plasmid. To distinguish the plasmid-derived ribosomal transcripts from those encoded by the rDNA locus, we inserted a tag of 18 base pairs within the first expansion segment of domain I of the 26S rRNA gene. We demonstrate that this insertion behaves as a neutral mutation since tagged 26S rRNA is normally processed and assembled into functional ribosomal subunits. This system allows us to study the effect of subsequent mutations within the tagged rDNA unit on the biosynthesis and function of the rRNA. As a first application, we wanted to ascertain whether the assembly of a 60S subunit is dependent on the presence in cis of an intact 17S rRNA gene. We found that a deletion of two-thirds of the 17S rRNA gene has no effect on the accumulation of active 60S subunits derived from the same operon. On the other hand, deletions within the second domain of the 26S rRNA gene completely abolished the accumulation of mature 26S rRNA.
Mol Cell Biol 1989 Feb
PMID:A system for the analysis of yeast ribosomal DNA mutations. 254 Apr 22


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