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Rouquette J, Choesmel V, Gleizes PE. Nuclear export and cytoplasmic processing of precursors to the 40S ribosomal subunits in mammalian cells. EMBO J 2005; 24:2862-72. [PMID: 16037817 PMCID: PMC1187937 DOI: 10.1038/sj.emboj.7600752] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2005] [Accepted: 06/28/2005] [Indexed: 11/09/2022] Open
Abstract
It is generally assumed that, in mammalian cells, preribosomal RNAs are entirely processed before nuclear exit. Here, we show that pre-40S particles exported to the cytoplasm in HeLa cells contain 18S rRNA extended at the 3' end with 20-30 nucleotides of the internal transcribed spacer 1. Maturation of this pre-18S rRNA (which we named 18S-E) involves a cytoplasmic protein, the human homolog of the yeast kinase Rio2p, and appears to be required for the translation competence of the 40S subunit. By tracking the nuclear exit of this precursor, we have identified the ribosomal protein Rps15 as a determinant of preribosomal nuclear export in human cells. Interestingly, inhibition of exportin Crm1/Xpo1 with leptomycin B strongly alters processing of the 5'-external transcribed spacer, upstream of nuclear export, and reveals a new cleavage site in this transcribed spacer. Completion of the maturation of the 18S rRNA in the cytoplasm, a feature thought to be unique to yeast, may prevent pre-40S particles from initiating translation with pre-mRNAs in eukaryotic cells. It also allows new strategies for the study of preribosomal transport in mammalian cells.
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MESH Headings
- Active Transport, Cell Nucleus/physiology
- Animals
- Blotting, Northern
- Cell Fractionation
- Cell Line, Tumor
- Cell Nucleus/metabolism
- Centrifugation, Density Gradient
- DNA Primers
- Fatty Acids, Unsaturated/pharmacology
- Green Fluorescent Proteins
- Humans
- In Situ Hybridization, Fluorescence
- Karyopherins/antagonists & inhibitors
- Mice
- Nuclear Proteins/metabolism
- RNA Interference
- RNA Precursors/metabolism
- RNA Processing, Post-Transcriptional/drug effects
- RNA Processing, Post-Transcriptional/physiology
- RNA Transport/physiology
- RNA, Ribosomal, 18S/metabolism
- Receptors, Cytoplasmic and Nuclear/antagonists & inhibitors
- Ribosomal Proteins
- Exportin 1 Protein
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Affiliation(s)
- Jacques Rouquette
- Laboratoire de Biologie Moléculaire des Eucaryotes and Institut d'Exploration Fonctionnelle des Génomes, CNRS and Université Paul Sabatier, Toulouse cedex, France
| | - Valérie Choesmel
- Laboratoire de Biologie Moléculaire des Eucaryotes and Institut d'Exploration Fonctionnelle des Génomes, CNRS and Université Paul Sabatier, Toulouse cedex, France
| | - Pierre-Emmanuel Gleizes
- Laboratoire de Biologie Moléculaire des Eucaryotes and Institut d'Exploration Fonctionnelle des Génomes, CNRS and Université Paul Sabatier, Toulouse cedex, France
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2
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Hingorani K, Szebeni A, Olson MO. Mapping the functional domains of nucleolar protein B23. J Biol Chem 2000; 275:24451-7. [PMID: 10829026 DOI: 10.1074/jbc.m003278200] [Citation(s) in RCA: 203] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein B23 is a multifunctional nucleolar protein whose cellular location and characteristics strongly suggest that it is a ribosome assembly factor. The protein has nucleic acid binding, ribonuclease, and molecular chaperone activities. To determine the contributions of unique polypeptide segments enriched in certain classes of amino acid residues to the respective activities, several constructs that produced N- and C-terminal deletion mutant proteins were prepared. The C-terminal quarter of the protein was shown to be necessary and sufficient for nucleic acid binding. Basic and aromatic segments at the N- and C-terminal ends, respectively, of the nucleic acid binding region were required for activity. The molecular chaperone activity was contained in the N-terminal half of the molecule, with important contributions from both nonpolar and acidic regions. The chaperone activity also correlated with the ability of the protein to form oligomers. The central portion of the molecule was required for ribonuclease activity and possibly contains the catalytic site; this region overlapped with the chaperone-containing segment of the molecule. The C-terminal, nucleic acid-binding region enhanced the ribonuclease activity but was not essential for it. These data suggest that the three activities reside in mainly separate but partially overlapping segments of the polypeptide chain.
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Affiliation(s)
- K Hingorani
- Department of Biochemistry, University of Mississippi Medical Center, Jackson, Mississippi 39216, USA
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Eichler DC. Characterization of a nucleolar 2'-O-methyltransferase and its involvement in the methylation of mouse precursor ribosomal RNA. Biochimie 1994; 76:1115-22. [PMID: 7748946 DOI: 10.1016/0300-9084(94)90039-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A nucleolar 2'-O-methyltransferase, partially purified from isolated mouse nucleoli, catalyzes the methylation of each of the four nucleosides, although to different levels depending on the RNA substrate. Similar to most methyltransferases which use S-adenosyl-L-methionine (SAM) as the methyl donor, the nucleolar 2'-O-methyltransferase was shown to bind S-adenosyl-L-homocysteine (SAH) (Kd = 0.17 microM), a product of the transfer reaction, as tightly as SAM (Kd = 0.24 microM). Binding assays also demonstrated stereospecificity about the sulfonium center of SAM. The naturally occurring S-chiral form of SAM had a 10-fold higher binding affinity than the R-chiral form. In addition, the alpha-amino group of the methionine moiety and the 6-amino group of the adenine moiety were shown to be required for maximal binding. The relative high affinity for both SAM and SAH may reflect a mechanism by which ribosome biogenesis is, in part, coordinated with cell growth, since a decrease in SAM:SAH ratio correlates with decreasing levels of 2'-O-methylation. The availability of unmethylated, in vitro-derived rRNA transcripts has made it possible to explore questions relating to the specificity for the RNA substrate. Using an in vitro-derived 28S rRNA transcript, the enzyme selectively methylated the sequence AmGmCm that occurs in a single-stranded bridge spanning two highly conserved structural domains of 28S rRNA. These results demonstrated that the purified nucleolar 2'-O-methyltransferase was sufficient to accurately methylate this region of 28S rRNA, and were taken to support the involvement of this nucleolar enzyme in the posttranscriptional methylation of the 47S precursor ribosomal RNA transcript.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- D C Eichler
- Department of Biochemistry and Molecular Biology, College of Medicine, University of South Florida, Tampa 33612, USA
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Eichler DC, Craig N. Processing of eukaryotic ribosomal RNA. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1994; 49:197-239. [PMID: 7863007 DOI: 10.1016/s0079-6603(08)60051-3] [Citation(s) in RCA: 162] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In summary, it can be argued that the understanding of eukaryotic rRNA processing is no less important than the understanding of mRNA maturation, since the capacity of a cell to carry out protein synthesis is controlled, in part, by the abundance of ribosomes. Processing of pre-rRNA is highly regulated, involving many cellular components acting either alone or as part of a complex. Some of these components are directly involved in the modification and cleavage of the precursor rRNA, while others direct the packaging of the rRNA into ribosome subunits. As is the case for pre-mRNA processing, snoRNPs are clearly involved in eukaryotic rRNA processing, and have been proposed to assemble with other proteins into at least one complex called a "processosome" (17), which carries out the ordered processing of the pre-rRNA and its assembly into ribosomes. The formation of a processing complex clearly makes possible the regulation required to coordinate the abundance of ribosomes with the physiological and developmental changes of a cell. It may be that eukaryotic rRNA processing is even more complex than pre-mRNA maturation, since pre-rRNA undergoes extensive nucleotide modification and is assembled into a complex structure called the ribosome. Undoubtedly, features of the eukaryotic rRNA-processing pathway have been conserved evolutionarily, and the genetic approach available in yeast research (6) should provide considerable knowledge that will be useful for other investigators working with higher eukaryotic systems. Interestingly, it was originally hoped that the extensive work and understanding of bacterial ribosome formation would provide a useful paradigm for the process in eukaryotes. However, although general features of ribosome structure and function are highly conserved between bacterial and eukaryotic systems, the basic strategy in ribosome biogenesis seems to be, for the most part, distinctly different. Thus, the detailed molecular mechanisms for rRNA processing in each kingdom will have to be independently deciphered in order to elucidate the features and regulation of this important process for cell survival.
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Affiliation(s)
- D C Eichler
- Department of Biochemistry & Molecular Biology, University of South Florida College of Medicine, Tampa 33612
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5
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Pantopoulos K, Georgatsos JG. Ribonucleases of diverse specificities in rabbit brain nuclei. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 207:1045-51. [PMID: 1499550 DOI: 10.1111/j.1432-1033.1992.tb17141.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A salt extract of rabbit brain nuclei contains three endoribonucleases, designated RNases Y, A and R, which produce acid-soluble products when incubated at near-neutral pH in the absence of metal ions. RNases Y and A yield products with the monoesterified phosphate at the 3' position, through 2',3'-(cyclic)phosphate intermediates. Oligonucleotides terminating with a 2',3'-(cyclic)phosphate are the end-products of the action of RNase R. Double-stranded substrates are highly resistant to the action of all enzymes. On the basis of limited hydrolysis of end-labelled 5S RNA, the three enzymes differ in their preference for the susceptible phosphodiester bond. Thus, RNase Y hydrolyses preferentially the YpN bond, RNase A the ApN bond and RNase R the RpU bond where R is guanosine in most cases. The advantages and disadvantages of using homopolyribonucleotides and dephosphorylated dinucleotides and trinucleotides in determining various aspects of the specificity of RNases are discussed.
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Affiliation(s)
- K Pantopoulos
- Laboratory of Biochemistry, School of Chemistry, University of Thessaloniki, Greece
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Vavatsi NA, Kouidou SA, Triantos AA, Kavoukopoulos EM, Papageorgiou GE, Trakatellis AC. Cellular and tissue distribution of a single-strand-specific nuclease. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1991; 23:27-31. [PMID: 1708732 DOI: 10.1016/0020-711x(91)90005-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
1. Specific antibodies which were raised against a single-strand-specific nuclease isolated from rat liver microsomes were used for characterizing this enzyme and determining its cellular and tissue distribution. 2. The single-strand-specific nuclease does not show any homology with other known nucleolytic enzymes. 3. It is mainly localized in microsomes and cytosol; traces of it are also found in nuclei, but it could not be detected in mitochondria. 4. Using the same specific antibodies we attempted to detect this nuclease in some other tissues which exhibit high metabolic rates, namely kidneys, heart and spleen. 5. Thus, with the aid of immunological techniques we were able to determine that at least part of the total poly(U) nucleolytic activity observed in kidney and heart is due to a nuclease immunologically identical to the enzyme under study. Kidneys were the best source for this enzyme.
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Affiliation(s)
- N A Vavatsi
- Department of Biological Chemistry, School of Medicine, Aristotelian University of Thessaloniki, Greece
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7
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Shumard CM, Eichler DC. Ribosomal RNA processing. Limited cleavages of mouse preribosomal RNA by a nucleolar endoribonuclease include the early +650 processing site. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(19)77640-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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8
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Kouidou SA, Triantos AA, Papageorgiou GE, Kavoukopoulos EM, Vavatsi NA, Trakatellis AC. Single-strand-specific nuclease from rat liver endoplasmic reticulum: characterization and mode of action. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1987; 19:857-64. [PMID: 2826268 DOI: 10.1016/0020-711x(87)90246-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
1. The characteristics and mode of action of a single-strand-specific nuclease isolated from rat liver endoplasmic reticulum are investigated with respect to its DNA and RNA substrates. 2. The RNase activity of the enzyme is slightly influenced by the presence of divalent cations but the DNase activity is enhanced by divalent cations particularly Mn2+. 3. Activity is partially inhibited by the presence of EGTA; this effect is reversed most efficiently by the addition of Mn2+. 4. The enzyme exhibits small pH dependence between pH 6-9 and maximum activity is observed at pH 7-7.5 for both DNase and RNase activities. 5. Sulfhydryl group reagents do not affect its action but histidyl group reagents exert a small but definite effect. 6. The enzyme degrades DNA and RNA endonucleolytically producing fragments which possess 3'-OH and 5'-phosphate termini. 7. Monomers are not produced even after prolonged degradation. 8. The end product of poly(U)degradation ranges between two and four building blocks but the DNA product is longer probably due to considerable percentage of secondary structure.
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Affiliation(s)
- S A Kouidou
- Department of Biological Chemistry, School of Medicine, Aristotelian University of Thessaloniki, Greece
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Kumagai H, Abiko T, Ono C, Marumo Y, Enomoto S, Igarashi K, Hirose S. Purification and mode of action of a microsomal endoribonuclease from rat liver. BIOCHIMICA ET BIOPHYSICA ACTA 1985; 827:424-30. [PMID: 2982410 DOI: 10.1016/0167-4838(85)90228-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
An endoribonuclease has been purified nearly to homogeneity from rat liver microsomes, and its mode of action and general properties were studied. The enzyme had an apparent molecular weight of 58 000, as estimated by both gel filtration and SDS-polyacrylamide gel electrophoresis and produced oligonucleotides from poly(A), poly(U) and poly(C). No mononucleotide was obtained by the enzymatic hydrolysis of the above substrates. The enzyme made endonucleolytic cleavages which generated 5'-phosphate-terminated oligonucleotides. It was suggested that the existence of at least (Ado5'P)2 residues at both sides of the cleavage bond was necessary for the action of the endoribonuclease. Divalent cations (Mg2+ or Mn2+) were required for the enzymatic activity, while K+ inhibited the enzyme. Spermine stimulated the enzymatic activity in the presence of 1 mM Mg2+.
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Lasater LS, Eichler DC. Isolation and properties of a single-strand 5'----3' exoribonuclease from Ehrlich ascites tumor cell nucleoli. Biochemistry 1984; 23:4367-73. [PMID: 6207856 DOI: 10.1021/bi00314a019] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A single-strand-specific, nucleolar exoribonuclease from Ehrlich ascites tumor cells has been isolated and purified free from other nucleases. The exonuclease degraded single-stranded RNA processively from either a 5'-hydroxyl or a 5'-phosphorylated end and released 5'-mononucleotides. The enzyme digested single-strand poly(C), poly(U), and poly(A) equally well but did not degrade duplex poly(C).poly(I) or poly(A).poly(U). Less than 0.2% of duplex DNA or 1.5% of heat-denatured DNA was degraded under the conditions which resulted in greater than 26% degradation of RNA. The ribonuclease required Mg2+ (0.2 mM) for optimum activity and was inhibited by ethylenediaminetetraacetic acid but not by human placental RNase inhibitor. The native enzyme had a Stokes radius of 42 A and a sedimentation coefficient (S20,w) of 4.3 S. From these values, an apparent molecular weight of 76 000 was derived by using the Svedberg equation. The localization and unique mode of degradation suggest a role for the 5'----3' exoribonuclease in ribosomal RNA processing.
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11
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Inhibition of protein synthesis in a polyribosome-dependent cell-free system by a specific ribonuclease prepared from the follicles of two different stages of development of the silkmothAntherea pernyi. ACTA ACUST UNITED AC 1984; 194:25-31. [DOI: 10.1007/bf00848950] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/1984] [Accepted: 06/04/1984] [Indexed: 11/25/2022]
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13
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Bachmann M, Trautmann F, Messer R, Zahn RK, Meyer zum Büschenfelde KH, Müller WE. Association of a polyuridylate-specific endoribonuclease with small nuclear ribonucleo-proteins which had been isolated by affinity chromatography using antibodies from a patient with systemic lupus erythematosus. EUROPEAN JOURNAL OF BIOCHEMISTRY 1983; 136:447-51. [PMID: 6227485 DOI: 10.1111/j.1432-1033.1983.tb07762.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Immunoglobulins, containing antibodies against U1-snRNP, have been prepared from a patient with systemic lupus erythematosus. After coupling these antibodies to a Sepharose matrix, U-snRNPs have been isolated and purified from rat liver nuclei by use of immunoaffinity chromatography. The resulting RNPs had the typical protein pattern of U-sn RNPs and a sedimentation coefficient of 12 S. The U-snRNP preparation was associated with an endoribonuclease which required Mg2+ for optimal activity. The enzyme, with an pH optimum of 6.2, degraded only poly(U). Other single-stranded polyribo- and polydeoxyribonucleotides, tRNA, as well as double-stranded RNA and DNA were not digested. The products of a terminal digestion are (U)6-12 with 3'-OH and 5'-P termini. The possible involvement of this endoribonuclease in the splicing of hnRNA is discussed.
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14
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Eichler DC, Eales SJ. The effect of RNA secondary structure on the action of a nucleolar endoribonuclease. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(17)44604-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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15
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Engelke DR, Shastry BS, Roeder RG. Multiple forms of DNA-dependent RNA polymerases in Xenopus laevis. Rapid purification and structural and immunological properties. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(18)33077-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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