101
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Abstract
The cause of premature ejaculation (PE) has been thought to be psychological in the majority of patients but we investigated penile hypersensitivity for an organic basis of PE. For another organic basis of PE, we have suggested hyperexcitability of the ejaculation center. SS-cream is a topical agent containing 9 oriental herbs for treating PE. Clinically SS-cream has been effective in the treatment of PE. Therefore, in order to implicate the organic basis of PE and realize the effect of SS-cream on PE, we investigated the somatosensory evoked potential (SEP) in patients with PE(16 cases) and the effects of SS-cream on SEP for treating PE. The latencies and amplitudes of the evoked responses were measured by two different places in stimuli, one was on the penile shaft with ring electrode and the other on the glans penis with a surface electrode. The latency of SEP stimulated at the glans penis was significantly longer than that stimulated at the penile shaft (p < 0.05). The latency stimulated at the glans penis after applying SS-cream was significantly longer than before applying SS-cream (p < 0.05), which was near the level of a normal potent man. But the latency stimulated at the penile shaft has no significant difference between before and after the application of SS-cream (P > 0.05). The amplitudes of the evoked responses stimulated at the glans penis were significantly higher than those stimulated at penile shaft (p < 0.05). And both these amplitudes were significantly reduced with the application of SS-cream (p < 0.05). With these result, we can suggest that the patients with PE have glans penile hyperexcitability and it provides further implications for an organic basis of PE, SEP stimulated at the glans penis can be a very useful method to evaluate PE, along with SEP stimulated a penile shaft and SS-cream prolongs the sensory conduction and reduces the penile hyperexcitability of the patient with PE.
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Affiliation(s)
- Z C Xin
- Department of Urology, University College of Medicine, Seoul, Korea
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102
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Choi Y, Ahn JH, Choi YD, Lee JS. Tissue-specific and developmental regulation of a gene encoding a low molecular weight sulfur-rich protein in soybean seeds. Mol Gen Genet 1995; 246:266-8. [PMID: 7862099 DOI: 10.1007/bf00294691] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A gene corresponding to a cDNA clone, SE60, encoding a low molecular weight sulfur-rich protein in soybean seeds was isolated from a soybean genomic library and characterized at the nucleotide level. The SE60 gene is interrupted by an intervening sequence of 694 bp in size. The 5' flanking region of the gene contained various regulatory sequences such as the RY repeat and CACA elements found in other seed protein genes of legumes. The SE60 gene encoded a preprotein of 75 amino acids, having a signal sequence of 28 amino acids at the N-terminus. The mature protein of 47 amino acids was basic and cysteine-rich. Northern blot analysis suggested that the SE60 gene is expressed in a tissue-specific and developmentally regulated manner during soybean seed development. The SE60 genes form a small multigene family composed of about four members in the soybean genome.
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Affiliation(s)
- Y Choi
- Department of Molecular Biology, Seoul National University, Korea
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103
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Kim YK, Baek JM, Park HY, Choi YD, Kim SI. Isolation and characterization of cDNA clones encoding class I chitinase in suspension cultures of rice cell. Biosci Biotechnol Biochem 1994; 58:1164-6. [PMID: 7765038 DOI: 10.1271/bbb.58.1164] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We have cloned and determined the nucleotide sequences of full-length cDNA clones for chitinase, CH6 and CH16, whose sizes were about 1.1 kb with signal peptides, from rice cell suspension cultures. Northern blot analysis with CH16 as a probe showed that the chitinase transcript reached maximum at 8 h after elicitor-treatment and their sizes were about 1.1 kb, demonstrating that these clones were induced by elicitor.
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Affiliation(s)
- Y K Kim
- Department of Agricultural Chemistry, College of Agriculture and Life Sciences, Seoul National University, Suwon, Korea
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104
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Baek JM, Song JC, Choi YD, Kim SI. Nucleotide sequence homology of cDNAs encoding soybean Bowman-Birk type proteinase inhibitor and its isoinhibitors. Biosci Biotechnol Biochem 1994; 58:843-6. [PMID: 7764974 DOI: 10.1271/bbb.58.843] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The sequences of cDNA clones encoding the Bowman-Birk proteinase inhibitor (BBPI) and its isoinhibitors (D-II and C-II) have been identified. Nucleotide sequence homologies among these clones and between the two reactive domains in each clone were very high. These homologies suggest that the BBPI and its isoinhibitor genes may have evolved from a common ancestral inhibitor. Also, clone pB2 (D-II) had two identical reactive sites that inhibit trypsin only, and three repetitive regions that are about 81 bp and initiated with ATG. It was assumed from these results that isoinhibitor D-II was the most primordial type of these inhibitors.
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Affiliation(s)
- J M Baek
- Department of Agricultural Chemistry, College of Agriculture and Life Sciences, Seoul National University, Suwon, Korea
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105
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Lee YH, Park EH, Kim WC, Choi YD, Park JH. [A case of pelvic paragonimiasis combined with myoma uteri and pelvic inflammatory disease]. Korean J Parasitol 1993; 31:295-7. [PMID: 8241090 DOI: 10.3347/kjp.1993.31.3.295] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Paragonimus westermani is a lung fluke of humans that is usually found in the lungs but may be found elsewhere in many unusual locations. A case of pelvic paragonimiasis was found incidentally by surgical intervention of inflammatory disease and myoma uteri. She was a 51-year-old Korean woman complaining of lower abdominal pain and intermittent vaginal spotting. Numerous Paragonimus ova were observed in the resected omentum in the pelvis after total abdominal hysterectomy. It is suggested that pelvic paragonimiasis may be one of causative agents of pelvic inflammatory disease.
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Affiliation(s)
- Y H Lee
- Department of Obstetrics & Gynecology, ChungAng Gil General Hospital, Inchon, Korea
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106
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Song SI, Kim CH, Baek SJ, Choi YD. Nucleotide sequences of cDNAs encoding the precursors for soybean (Glycine max) trypsin inhibitors (Kunitz type). Plant Physiol 1993; 101:1401-2. [PMID: 8310071 PMCID: PMC160669 DOI: 10.1104/pp.101.4.1401] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Affiliation(s)
- S I Song
- Department of Agricultural Chemistry, Seoul National University, Korea
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107
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Choi Y, Choi YD, Lee JS. Nucleotide sequence of a cDNA encoding a low molecular weight sulfur-rich protein in soybean seeds. Plant Physiol 1993; 101:699-700. [PMID: 8278516 PMCID: PMC160625 DOI: 10.1104/pp.101.2.699] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Affiliation(s)
- Y Choi
- Department of Molecular Biology, Seoul National University, Korea
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108
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Kim IC, Cha JH, Kim JR, Jang SY, Seo BC, Cheong TK, Lee DS, Choi YD, Park KH. Catalytic properties of the cloned amylase from Bacillus licheniformis. J Biol Chem 1992; 267:22108-14. [PMID: 1385394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
A gene encoding a new amylolytic enzyme of Bacillus licheniformis (BLMA) has been cloned, and we characterized the enzyme expressed in Escherichia coli. The genomic DNA of B. licheniformis was double-digested with EcoRI and BamHI and ligated the pBR322. The transformed E. coli was selected by its amylolytic activity, which carries the recombinant plasmid pIJ322 containing a 3.5-kilobase fragment of B. licheniformis DNA. The purified enzyme encoded by pIJ322 was capable of hydrolyzing pullulan and cyclodextrin as well as starch. It was active over a pH range of 6-8 and its optimum temperature was 50 degrees C. The molecular weight of the enzyme was 64,000, and the isoelectric point was 5.4. It degraded soluble starch by cleaving maltose units preferentially but did not attack alpha-1,6-linkage. The enzyme also hydrolyzed pullulan to panose units exclusively. In the presence of glucose, however, it transferred the panosyl moiety to glucose with the formation of alpha-1,6-linkage. The specificity of transferring activity is evident from the result of the maltosyl-transferring reaction which produces isopanose from maltotriose and glucose. The molecular structure of the enzyme deduced from the nucleotide sequence of the clone maintains limited similarity in the conserved regions to the other amylolytic enzymes.
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Affiliation(s)
- I C Kim
- Research Center for New Biomaterials in Agriculture, Seoul National University, Suwon, Korea
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109
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Affiliation(s)
- J H Kim
- Department of Biological Science and Engineering, Korea Advanced Institute of Science and Technology, (KAIST), Seoul
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110
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Kim JH, Choi YD, Byun SM. Molecular cloning of non-polyadenylated nuclear hnRNAs. Biotechnol Lett 1990. [DOI: 10.1007/bf01022420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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111
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Piñol-Roma S, Choi YD, Dreyfuss G. Immunological methods for purification and characterization of heterogeneous nuclear ribonucleoprotein particles. Methods Enzymol 1990; 181:317-25. [PMID: 2143256 DOI: 10.1016/0076-6879(90)81132-e] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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112
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Abstract
Heterogeneous nuclear RNAs (hnRNAs), some of which are mRNA precursors, and the mature mRNAs are associated in eukaryotic cells with specific proteins to form ribonucleoprotein complexes (RNP). The RNP proteins are likely to play a major role in the formation, packaging, processing, and function of mRNA. The major proteins that interact with hnRNA and with mRNA were identified by photochemical RNA-protein cross-linking in intact cells and monoclonal antibodies to several of these proteins were produced. Using these antibodies the hnRNP proteins were characterized and the hnRNP complex was isolated from vertebrate cell nuclei. The hnRNP complex is a unitary structure of consistent, defined and conserved components. The proteins of the hnRNP complex were identified and the general organization of hnRNA and proteins in the hRNP complex were studied.
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Affiliation(s)
- G Dreyfuss
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60201
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113
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114
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Piñol-Roma S, Choi YD, Matunis MJ, Dreyfuss G. Immunopurification of heterogeneous nuclear ribonucleoprotein particles reveals an assortment of RNA-binding proteins. Genes Dev 1988; 2:215-27. [PMID: 3129338 DOI: 10.1101/gad.2.2.215] [Citation(s) in RCA: 352] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Heterogeneous nuclear RNA-ribonucleoprotein (hnRNP) particles can be efficiently purified by a specific, rapid, and mild procedure using monoclonal antibodies to hnRNP proteins. We report here on the detailed analysis of the protein composition of immunopurified hnRNP particles from human HeLa cells. By two-dimensional gel electrophoresis, immunopurified hnRNP particles contain at least 24 polypeptides in the range of 34,000-120,000 daltons. The abundant 30,000-40,000 dalton proteins, A, B, and C, described previously, are a subset of these polypeptides. The protein compositions of hnRNP particles found in the nucleoplasm fraction and in the chromatin-nucleolar fraction are very similar. Upon addition of the polyanion heparin, most of the major proteins remain associated in heparin-resistant particles, and only several, mostly minor, proteins dissociate. This provides an aid in the classification of the proteins and an additional criterion for the definition of hnRNP particle components. Chromatography on single-stranded DNA (ssDNA)-agarose in a heparin- and moderate or high salt (higher than 300 mM NaCl)-resistant manner suggests that most, if not all, of these proteins are single-stranded nucleic acid-binding proteins. We describe a general method for the large-scale purification of hnRNP proteins by affinity chromatography on ssDNA columns and its use for the production of new monoclonal antibodies to hnRNP proteins.
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Affiliation(s)
- S Piñol-Roma
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208
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115
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Abstract
Splicing in vitro of a messenger RNA (mRNA) precursor (pre-mRNA) is inhibited by a monoclonal antibody to the C proteins (anti-C) of the heterogeneous nuclear RNA (hnRNA)-ribonucleoprotein (hnRNP) particles. This antibody, 4F4, inhibits an early step of the reaction: cleavage at the 3' end of the upstream exon and the formation of the intron lariat. In contrast, boiled 4F4, or a different monoclonal antibody (designated 2B12) to the C proteins, or antibodies to other hnRNP proteins (120 and 68 kilodaltons) and nonimmune mouse antibodies have no inhibitory effect. The 4F4 antibody does not prevent the adenosine triphosphate-dependent formation of a 60S splicing complex (spliceosome). Furthermore, the 60S splicing complex contains C proteins, and it can be immunoprecipitated with 4F4. Depletion of C proteins from the splicing extract by immunoadsorption with either of the two monoclonal antibodies to the C proteins (4F4 or 2B12) results in the loss of splicing activity, whereas mock-depletion with nonimmune mouse antibodies bodies has no effect. A 60S splicing complex does not form in a C protein-depleted nuclear extract. These results indicate an essential role for proteins of the hnRNP complex in the splicing of mRNA precursors.
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116
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Abstract
The interaction of mRNA with proteins in vesicular stomatitis virus (VSV)-infected cells was studied by photochemical cross-linking in intact cells. The major [35S]methionine-labeled proteins which became cross-linked by UV light to mRNA in uninfected and in VSV-infected HeLa cells were similar and had apparent mobilities in sodium dodecyl sulfate-polyacrylamide gel electrophoresis corresponding to 135, 93, 72, 68, 53, 50, 43, and 36 kilodaltons. The proteins which were cross-linked in vivo specifically to the five mRNAs of VSV were labeled through radioactive nucleotides incorporated only into VSV mRNAs under conditions (5 micrograms of actinomycin D per ml) in which only VSV mRNAs are labeled. The same major mRNP proteins that became cross-linked to host mRNAs also became cross-linked to VSV mRNAs, although several quantitative differences were detected. Photochemical cross-linking and immunoblotting of cross-linked mRNPs with VSV antiserum demonstrated that in addition to host proteins VSV mRNAs also became cross-linked to the VSV-encoded N protein. The poly(A) segment of both host and VSV mRNAs was associated in vivo selectively with the 72-kilodalton polypeptide. The major proteins of mRNA-ribonucleoprotein complexes are therefore ubiquitous and common to different mRNAs. Furthermore, since the major messenger ribonucleoproteins interact also with VSV mRNAs even though these mRNAs are transcribed in the cytoplasm, it appears that nuclear transcription and nucleocytoplasmic transport are not necessary for mRNA to interact with these proteins.
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117
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Choi YD, Dreyfuss G. Isolation of the heterogeneous nuclear RNA-ribonucleoprotein complex (hnRNP): a unique supramolecular assembly. Proc Natl Acad Sci U S A 1984; 81:7471-5. [PMID: 6594697 PMCID: PMC392168 DOI: 10.1073/pnas.81.23.7471] [Citation(s) in RCA: 144] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The packaging of heterogeneous nuclear RNA (hnRNA), the fate of hnRNA in the nucleus, and the conversion of hnRNA to mRNA are believed to occur as the hnRNA transcript is associated with specific proteins to form a ribonucleoprotein complex termed the hnRNP complex. The identity and organization of the protein constituents of the hnRNP have been a matter of considerable controversy. We report here the isolation of the hnRNP complex from vertebrate cell nuclei, employing immunoprecipitation with monoclonal antibodies against the major proteins that are in contact with hnRNA in HeLa cells. Rapid immunoprecipitation from HeLa nucleoplasm with two different monoclonal antibodies to the hnRNP C proteins (41 and 43 kDa) isolates a similar complex that contains proteins and hnRNA of up to approximately equal to 10 kilobases. The major steady-state [35S]methionine-labeled proteins of the isolated complex are of 34 kDa, 36 kDa (A1 and A2), 37 kDa, 38 kDa (B1 and B2), 41 kDa, 43 kDa (C1 and C2), and doublets at 68 kDa and at 120 kDa. Additional proteins from 45 kDa to very high molecular mass are also seen. The major proteins of the complex appear identical by NaDodSO4/polyacrylamide gel electrophoresis to genuine hnRNP proteins--those which become crosslinked by UV light to the hnRNA in vivo. Immunoprecipitation with a different, noncrossreacting monoclonal antibody to the 120-kDa protein isolates an apparently identical complex of proteins that are present at a similar relative stoichiometry. Similar hnRNP complexes are found in rodent and avian cells. Nuclease digestions indicate that RNA plays a role in maintaining the integrity of the structure and that intact RNA of approximately equal to 125 nucleotides is sufficient to hold the complex of proteins together. The coimmunoprecipitation of the hnRNA and of all of the proteins through antibodies against different genuine hnRNP proteins and from divergent species strongly suggests that the hnRNP complex is a unitary structure of consistent, defined, and conserved components.
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118
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Choi YD, Dreyfuss G. Monoclonal antibody characterization of the C proteins of heterogeneous nuclear ribonucleoprotein complexes in vertebrate cells. J Biophys Biochem Cytol 1984; 99:1997-204. [PMID: 6209285 PMCID: PMC2113551 DOI: 10.1083/jcb.99.6.1997] [Citation(s) in RCA: 180] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The C proteins (C1 and C2) are major constituents of the 40S subparticle of heterogeneous nuclear ribonucleoprotein complexes (hnRNPs) (Beyer, A.L., M.E. Christensen, B.W. Walker, and W.M. LeStourgeon, 1977, Cell, 11:127-138) and are two of the most prominent proteins that become cross-linked by ultraviolet light to heterogeneous nuclear RNA (hnRNA) in vivo. Studies are described here on the characterization of the C proteins in vertebrate cells using monoclonal and polyclonal antibodies. Monoclonal antibodies to genuine RNP proteins, including the C proteins, were obtained by immunizing mice with purified complexes of poly(A)+ hnRNA and poly(A)+ mRNA with their contacting proteins in vivo obtained by ultraviolet cross-linking the complexes in intact cells (Dreyfuss, G., Y.D. Choi, and S.A. Adam, 1984, Mol. Cell. Biol., 4:1104-1114). One of the monoclonal antibodies identified the C proteins in widely divergent species ranging from human to lizard. In all species examined, there were two C proteins in the molecular weight range of from 39,000 to 42,000 for C1, and from 40,000 to 45,000 for C2. The two C proteins were found to be highly related to each other; they were recognized by the same monoclonal antibodies and antibodies raised against purified C1 reacted also with C2. In avian, rodent, and human cells the C proteins were phosphorylated and were in contact with hnRNA in vivo. Immunofluorescence microscopy demonstrated that the C proteins are segregated to the nucleus. Within the nucleus the C proteins were not found in nucleoli and were not associated with chromatin as seen in cells in prophase. These findings demonstrate that C proteins with similar characteristics to those in humans are ubiquitous components of hnRNPs in vertebrates.
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119
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Abstract
Exposure of cells to UV light of sufficient intensity brings about cross-linking of RNA to proteins which are in direct contact with it in vivo. The major [35S]methionine-labeled proteins which become cross-linked to polyadenylated heterogeneous nuclear RNA in HeLa cells have molecular weights of 120,000 (120K), 68K, 53K, 43K, 41K, 38K, and 36K. Purified complexes of polyadenylated RNA with proteins obtained by UV cross-linking in intact cells were used to immunize mice and generate monoclonal antibodies to several of these proteins. Some properties of three of the proteins, 41K, 43K, and 120K, were characterized with these antibodies. The 41K and 43K polypeptides are highly related. They were recognized by the same antibody (2B12) and have identical isoelectric points (pl = 6.0 +/- 0.2) but different partial peptide maps. The 41K and 43K polypeptides were part of the 40S heterogeneous nuclear ribonucleoprotein particle and appear to correspond to the previously described C proteins (Beyer et al., Cell II:127-138, 1977). A different monoclonal antibody (3G6) defined a new major heterogeneous ribonucleoprotein of 120K. The 41K, 43K, and 120K polypeptides were associated in vivo with both polyadenylated and non-polyadenylated nuclear RNA, and all three proteins were phosphorylated. The monoclonal antibodies recognized similar proteins in human and monkey cells but not in several other vertebrates. Immunofluorescence microscopy demonstrated that these proteins are segregated to the nucleus, where they are part of a fine particulate nonnucleolar structure. In cells extracted in situ with nonionic detergent, all of the 41K and 43K polypeptides were associated with the nucleus at salt concentrations up to 0.5 M NaCl, whereas the 120K polypeptide was completely extracted at this NaCl concentration. A substantial fraction of the 41K and 43K polypeptides (up to 40%) was retained with a nuclear matrix--a structure which is resistant to digestion with DNase I and to extraction by 2 M NaCl, but the 41K and 43K polypeptides were quantitatively removed at 0.5 M NaCl after digestion with RNase.
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120
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Dreyfuss G, Adam SA, Choi YD. Physical change in cytoplasmic messenger ribonucleoproteins in cells treated with inhibitors of mRNA transcription. Mol Cell Biol 1984; 4:415-23. [PMID: 6717428 PMCID: PMC368718 DOI: 10.1128/mcb.4.3.415-423.1984] [Citation(s) in RCA: 128] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Exposure of intact cells to UV light brings about cross-linking of polyadenylated mRNA to a set of cytoplasmic proteins which are in direct contact with the mRNA in vivo. Substantial amounts of an additional protein of molecular weight 38,000 (38K) become cross-linked to the mRNA when cells are treated with inhibitors of mRNA synthesis (actinomycin D, camptothecin, and 5,6-dichloro-1-beta-D-ribofuranosyl benzimidazole) or after infection with vesicular stomatitis virus. Cordycepin, which inhibits polyadenylation but not mRNA synthesis, has no such effect. Inhibitors of protein synthesis and of rRNA synthesis are also without effect on 38K cross-linking to mRNA. The onset of the effect of inhibitors of mRNA synthesis on the UV cross-linkable interaction between mRNA and 38K is rapid and reaches a maximal level in less than 60 min, and it is completely and rapidly reversible. In cells treated with actinomycin D, the amount of 38K which becomes cross-linked to mRNA is proportional to the extent of inhibition of mRNA synthesis. The association of 38K with mRNA during transcriptional arrest does not require protein synthesis because simultaneous treatment with the protein synthesis inhibitor emetine does not interfere with it. The effectors which promote the interaction of 38K with mRNA do not affect the proteins which are in contact with polyadenylated heterogeneous nuclear RNA and do not markedly affect protein synthesis in the cell. The 38K protein can be isolated with the polyribosomal polyadenylated fraction from which it was purified, and monoclonal antibodies against it were prepared. Immunofluorescence microscopy shows mostly cytoplasmic and some nuclear staining. These observations demonstrate that commonly used inhibitors of transcription affect the physical state of messenger ribonucleoproteins in vivo.
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