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Tsai KC, Zhang YX, Kao HY, Fung KM, Tseng TS. Pharmacophore-driven identification of human glutaminyl cyclase inhibitors from foods, plants and herbs unveils the bioactive property and potential of Azaleatin in the treatment of Alzheimer's disease. Food Funct 2022; 13:12632-12647. [PMID: 36416361 DOI: 10.1039/d2fo02507h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Alzheimer's disease (AD) is the leading cause of disabilities in old age and a rapidly growing condition in the elderly population. AD brings significant burden and has a devastating impact on public health, society and the global economy. Thus, developing new therapeutics to combat AD is imperative. Human glutaminyl cyclase (hQC), which catalyzes the formation of neurotoxic pyroglutamate (pE)-modified β-amyloid (Aβ) peptides, is linked to the amyloidogenic process that leads to the initiation of AD. Hence, hQC is an essential target for developing anti-AD therapeutics. Here, we systematically screened and identified hQC inhibitors from natural products by pharmacophore-driven inhibitor screening coupled with biochemical and biophysical examinations. We employed receptor-ligand pharmacophore generation to build pharmacophore models and Phar-MERGE and Phar-SEN for inhibitor screening through ligand-pharmacophore mapping. About 11 and 24 hits identified from the Natural Product and Traditional Chinese Medicine databases, respectively, showed diverse hQC inhibitory abilities. Importantly, the inhibitors TCM1 (Azaleatin; IC50 = 1.1 μM) and TCM2 (Quercetin; IC50 = 4.3 μM) found in foods and plants exhibited strong inhibitory potency against hQC. Furthermore, the binding affinity and molecular interactions were analyzed by surface plasmon resonance (SPR) and molecular modeling/simulations to explore the possible modes of action of Azaleatin and Quercetin. Our study successfully screened and characterized the foundational biochemical and biophysical properties of Azaleatin and Quercetin toward targeting hQC, unveiling their bioactive potential in the treatment of AD.
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Affiliation(s)
- Keng-Chang Tsai
- National Research Institute of Chinese Medicine, Ministry of Health and Welfare, Taipei, Taiwan. .,Ph.D. Program in Medical Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
| | - Yi-Xuan Zhang
- Institute of Molecular Biology, National Chung Hsing University, Taichung, Taiwan.
| | - Hsiang-Yun Kao
- Institute of Molecular Biology, National Chung Hsing University, Taichung, Taiwan.
| | - Kit-Man Fung
- Institute of Molecular Biology, National Chung Hsing University, Taichung, Taiwan. .,Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan
| | - Tien-Sheng Tseng
- Institute of Molecular Biology, National Chung Hsing University, Taichung, Taiwan.
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2
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Abstract
Here we show that HDAC7, a member of the class II histone deacetylases, specifically targets several members of myocyte enhancer factors, MEF2A, -2C, and -2D, and inhibits their transcriptional activity. Furthermore, we demonstrate that DNA-bound MEF2C is capable of recruiting HDAC7, demonstrating that the HDAC7-dependent repression of transcription is not due to the inhibition of the MEF2 DNA binding activity. The data also suggest that the promoter bound MEF2 is potentially capable of remodeling adjacent nucleosomes via the recruitment of HDAC7. We have also observed a nucleocytoplasmic shuttling of HDAC7 and dissected the mechanism involved. In NIH3T3 cells, HDAC7 was primarily localized in the cytoplasm, essentially due to an active CRM1-dependent export of the protein from the nucleus. Interestingly, in HeLa cells, HDAC7 was predominantly nuclear. In these cells we could restore the cytoplasmic localization of HDAC7 by expressing CaMK I. This CaMK I-induced nuclear export of HDAC7 was abolished when three critical serines, Ser-178, Ser-344, and Ser-479, of HDAC7 were mutated. We show that these serines are involved in the direct interaction of HDAC7 with 14-3-3. Mutations of these serine residues weakened the association with 14-3-3 and dramatically enhanced the repression activity of HDAC7 in NIH3T3 cells, but not in HeLa cells. Data presented in this work clearly show that the signal dependent subcellular localization of HDAC7 is essential in controlling its activities. The data also show that the cellular concentration of factors such as 14-3-3, CaMK I, and other yet unknown molecules may determine the subcellular localization of an individual HDAC member in a cell type and HDAC-specific manner.
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Affiliation(s)
- H Y Kao
- Department of Biochemistry, School of Medicine, Case Western Reserve University, University Hospitals of Cleveland, 10900 Euclid Ave., Cleveland, OH 44106, USA.
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3
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Shi Y, Downes M, Xie W, Kao HY, Ordentlich P, Tsai CC, Hon M, Evans RM. Sharp, an inducible cofactor that integrates nuclear receptor repression and activation. Genes Dev 2001; 15:1140-51. [PMID: 11331609 PMCID: PMC312688 DOI: 10.1101/gad.871201] [Citation(s) in RCA: 257] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2000] [Accepted: 03/01/2001] [Indexed: 11/25/2022]
Abstract
A yeast two-hybrid screen using the conserved carboxyl terminus of the nuclear receptor corepressor SMRT as a bait led to the isolation of a novel human gene termed SHARP (SMRT/HDAC1 Associated Repressor Protein). SHARP is a potent transcriptional repressor whose repression domain (RD) interacts directly with SMRT and at least five members of the NuRD complex including HDAC1 and HDAC2. In addition, SHARP binds to the steroid receptor RNA coactivator SRA via an intrinsic RNA binding domain and suppresses SRA-potentiated steroid receptor transcription activity. Accordingly, SHARP has the capacity to modulate both liganded and nonliganded nuclear receptors. Surprisingly, the expression of SHARP is itself steroid inducible, suggesting a simple feedback mechanism for attenuation of the hormonal response.
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Affiliation(s)
- Y Shi
- Howard Hughes Medical Institute, The Salk Institute for Biological Studies, Gene Expression Laboratory, La Jolla, California 92037, USA
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4
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Abstract
Recent investigations have allowed the identification of an increasing number of distinct nuclear multi-component complexes containing several types of enzymatic activity. Many of the complexes containing histone deacetylases are believed to control transcription and chromatin remodeling. We suggest here that at least some of these abundant complexes are likely to be "molecular reservoirs" of dynamic composition that exchange factors with other less abundant and functional complexes, according to specific required activities.
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Affiliation(s)
- S Khochbin
- Laboratoire de Biologie Moléculaire et Cellulaire de la Différenciation, INSERM U309, Equipe chromatine et expression des gènes, Institut Albert Bonniot, Faculté de Médecine, Domaine de la Merci, 38706 La Tronche Cedex, France.
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5
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Tsai TH, Kao HY, Chen CF. Measurement and pharmacokinetic analysis of unbound cephaloridine in rat blood by on-line microdialysis and microbore liquid chromatography. Biomed Chromatogr 2001; 15:79-82. [PMID: 11268046 DOI: 10.1002/bmc.40] [Citation(s) in RCA: 7] [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: 11/12/2022]
Abstract
A technique involving rapid sampling of cephaloridine in rat blood was achieved using a combination of microdialysis and sensitive microbore liquid chromatography. A microdialysis probe was inserted into the jugular vein/right atrium of a Sprague-Dawley rat. Then after a real-time collection of the analyte by microdialysis, the dialysate was automatically injected into a liquid chromatographic system via an on-line injector. Following a 2 h stabilization period after the surgical procedure, cephaloridine (20 mg/kg, i.v.) was then administered via the femoral vein. Isocratic elution of cephaloridine was carried out with a mobile phase containing methanol-20 mM monosodium phosphate (25:75, v/v, pH 5.5), and the flow rate of the mobile phase was 0.05 mL/min within 10 min. Intra- and inter-assay accuracy and precision of the assay were each less than 10%. The in vivo recovery of the cephaloridine from the microdialysate was 49.7 +/- 8.0% and 42.4 +/- 8.4% for 0.5 and 1 microg/mL standards (n = 6), respectively. Based on the pharmacokinetic analysis, the elimination half-life was 32.2 +/- 8.6 min by cephaloridine administration (20 mg/kg, i.v., n = 6).
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Affiliation(s)
- T H Tsai
- National Research Institute of Chinese Medicine, 155-1 Li-Nong Street Section 2, Taipei 112, Taiwan.
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6
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Tsai TH, Kao HY, Chen CF. Measurement and pharmacokinetic analysis of unbound ceftazidime in rat blood using microdialysis and microbore liquid chromatography. J Chromatogr B Biomed Sci Appl 2001; 750:93-8. [PMID: 11204227 DOI: 10.1016/s0378-4347(00)00415-1] [Citation(s) in RCA: 4] [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] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
To evaluate the biodisposition of ceftazidime in rat blood, a rapid and simple microbore liquid chromatographic technique together with a microdialysis sampling technique were developed. This method involves an on-line design for blood dialysate directly injected into a microbore liquid chromatographic system. The chromatographic conditions consisted of a mobile phase of methanol-acetonitrile-100 mM monosodium phosphoric acid (pH 3.0) (10:10:80, v/v/v) pumped through a microbore reversed-phase column at a flow-rate of 0.05 ml/min. With the detection wavelength set at 254 nm, a good linear correlation was observed between the peak area and the ceftazidime concentration at 0.1 to 50 microg/ml (r=0.999). Microdialysis probes, being custom-made, were screened for acceptable in vivo recovery while chromatographic resolution and detection were validated for response linearity, as well as intra-day and inter-day variabilities. This method was then applied to the pharmacokinetic profiling of ceftazidime in blood following intravenous 50 mg/kg administration to rats. The pharmacokinetics was calculated from the corrected data for dialysate concentrations of ceftazidime versus time. This method has been used to study ceftazidime pharmacokinetics in rats and has proven to be rapid and reproducible.
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Affiliation(s)
- T H Tsai
- National Research Institute of Chinese Medicine, Taipei, Taiwan.
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Downes M, Ordentlich P, Kao HY, Alvarez JG, Evans RM. Identification of a nuclear domain with deacetylase activity. Proc Natl Acad Sci U S A 2000; 97:10330-5. [PMID: 10984530 PMCID: PMC27024 DOI: 10.1073/pnas.97.19.10330] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/03/2000] [Indexed: 11/18/2022] Open
Abstract
Here, we describe the identification and characterization of a nuclear body (matrix-associated deacetylase body) whose formation and integrity depend on deacetylase activity. Typically, there are 20-40 0.5-microM bodies per nucleus, although the size and number can vary substantially. The structure appears to contain both class I and the recently described class II histone deacetylases (HDAC)5 and 7 along with the nuclear receptor corepressors SMRT (silencing mediator for retinoid and thyroid receptor) and N-CoR (nuclear receptor corepressor). Addition of the deacetylase inhibitors trichostatin A and sodium butyrate completely disrupt these nuclear bodies, providing a demonstration that the integrity of a nuclear body is enzyme dependent. We demonstrate that HDAC5 and 7 can associate with at least 12 distinct proteins, including several members of the NuRD and Sin3A repression complexes, and appear to define a new but related complex.
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Affiliation(s)
- M Downes
- Howard Hughes Medical Institute, Gene Expression Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
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8
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Kao HY, Downes M, Ordentlich P, Evans RM. Isolation of a novel histone deacetylase reveals that class I and class II deacetylases promote SMRT-mediated repression. Genes Dev 2000; 14:55-66. [PMID: 10640276 PMCID: PMC316336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/1999] [Accepted: 11/29/1999] [Indexed: 02/15/2023]
Abstract
The transcriptional corepressor SMRT functions by mediating the repressive effect of transcription factors involved in diverse signaling pathways. The mechanism by which SMRT represses basal transcription has been proposed to involve the indirect recruitment of histone deacetylase HDAC1 via the adaptor mSin3A. In contrast to this model, a two-hybrid screen on SMRT-interacting proteins resulted in the isolation of the recently described HDAC5 and a new family member termed HDAC7. Molecular and biochemical results indicate that this interaction is direct and in vivo evidence colocalizes SMRT, mHDAC5, and mHDAC7 to a distinct nuclear compartment. Surprisingly, HDAC7 can interact with mSin3A in yeast and in mammalian cells, suggesting association of multiple repression complexes. Taken together, our results provide the first evidence that SMRT-mediated repression is promoted by class I and class II histone deacetylases and that SMRT can recruit class II histone deacetylases in a mSin3A-independent fashion.
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Affiliation(s)
- H Y Kao
- Howard Hughes Medical Institute, Gene Expression Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037 USA
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9
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Nagy L, Kao HY, Love JD, Li C, Banayo E, Gooch JT, Krishna V, Chatterjee K, Evans RM, Schwabe JW. Mechanism of corepressor binding and release from nuclear hormone receptors. Genes Dev 1999; 13:3209-16. [PMID: 10617570 PMCID: PMC317208 DOI: 10.1101/gad.13.24.3209] [Citation(s) in RCA: 332] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/1999] [Accepted: 11/04/1999] [Indexed: 11/25/2022]
Abstract
The association of transcription corepressors SMRT and N-CoR with retinoid and thyroid receptors results in suppression of basal transcriptional activity. A key event in nuclear receptor signaling is the hormone-dependent release of corepressor and the recruitment of coactivator. Biochemical and structural studies have identified a universal motif in coactivator proteins that mediates association with receptor LBDs. We report here the identity of complementary acting signature motifs in SMRT and N-CoR that are sufficient for receptor binding and ligand-induced release. Interestingly, the motif contains a hydrophobic core (PhixxPhiPhi) similar to that found in NR coactivators. Surprisingly, mutations in the amino acids that directly participate in coactivator binding disrupt the corepressor association. These results indicate a direct mechanistic link between activation and repression via competition for a common or at least partially overlapping binding site.
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Affiliation(s)
- L Nagy
- The Salk Institute for Biological Studies, Gene Expression Laboratory, La Jolla, California 92037 USA
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Asahara H, Dutta S, Kao HY, Evans RM, Montminy M. Pbx-Hox heterodimers recruit coactivator-corepressor complexes in an isoform-specific manner. Mol Cell Biol 1999; 19:8219-25. [PMID: 10567547 PMCID: PMC84906 DOI: 10.1128/mcb.19.12.8219] [Citation(s) in RCA: 119] [Impact Index Per Article: 4.8] [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] [Received: 06/28/1999] [Accepted: 09/08/1999] [Indexed: 11/20/2022] Open
Abstract
Homeobox (hox) proteins have been shown to regulate cell fate and segment identity by promoting the expression of specific genetic programs. In contrast to their restricted biological action in vivo, however, most homeodomain factors exhibit promiscuous DNA binding properties in vitro, suggesting a requirement for additional cofactors that enhance target site selectivity. In this regard, the pbx family of homeobox genes has been found to heterodimerize with and thereby augment the DNA binding activity of certain hox proteins on a subset of potential target sites. Here we examine the transcriptional properties of a forced hox-pbx heterodimer containing the pancreas-specific orphan homeobox factor pdx fused to pbx-1a. Compared to the pdx monomer, the forced pdx-pbx1a dimer, displayed 10- to 20-fold-higher affinity for a consensus hox-pbx binding site but was completely unable to bind a hox monomer recognition site. The pdx-pbx dimer stimulated target gene expression via an N-terminal trans-activation domain in pdx that interacts with the coactivator CREB binding protein. The pdx-pbx dimer was also found to repress transcription via a C-terminal domain in pbx-1a that associates with the corepressors SMRT and NCoR. The transcriptional properties of the pdx-pbx1 complex appear to be regulated at the level of alternative splicing; a pdx-pbx polypeptide containing the pbx1b isoform, which lacks the C-terminal extension in pbx1a, was unable to repress target gene expression via NCoR-SMRT. Since pbx1a and pbx1b are differentially expressed in endocrine versus exocrine compartments of the adult pancreas, our results illustrate a novel mechanism by which pbx proteins may modulate the expression of specific genetic programs, either positively or negatively, during development.
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Affiliation(s)
- H Asahara
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02215, USA
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11
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Tsai CC, Kao HY, Yao TP, McKeown M, Evans RM. SMRTER, a Drosophila nuclear receptor coregulator, reveals that EcR-mediated repression is critical for development. Mol Cell 1999; 4:175-86. [PMID: 10488333 DOI: 10.1016/s1097-2765(00)80365-2] [Citation(s) in RCA: 161] [Impact Index Per Article: 6.4] [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: 11/25/2022]
Abstract
The Drosophila ecdysone receptor (EcR)/ultraspiracle (USP) heterodimer is a key regulator in molting and metamorphoric processes, activating and repressing transcription in a sequence-specific manner. Here, we report the isolation of an EcR-interacting protein, SMRTER, which is structurally divergent but functionally similar to the vertebrate nuclear corepressors SMRT and N-CoR. SMRTER mediates repression by interacting with Sin3A, a repressor known to form a complex with the histone deacetylase Rpd3/HDAC. Importantly, we identify an EcR mutant allele that fails to bind SMRTER and is characterized by developmental defects and lethality. Together, these results reveal a novel nuclear receptor cofactor that exhibits evolutionary conservation in the mechanism to achieve repression and demonstrate the essential role of repression in hormone signaling.
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Affiliation(s)
- C C Tsai
- Gene Expression Lab, Salk Institute, La Jolla, California 92037, USA
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Affiliation(s)
- R J Lin
- Howard Hughes Medical Institute, Salk Institute for Biological Studies, La Jolla, California 92037, USA
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13
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Abstract
Nucleosomal histone modification is believed to be a critical step in the activation of RNA polymerase II-dependent transcription. p300/CBP and PCAF histone acetyltransferases (HATs) are coactivators for several transcription factors, including nuclear hormone receptors, p53, and Stat1alpha, and participate in transcription by forming an activation complex and by promoting histone acetylation. The adenoviral E1A oncoprotein represses transcriptional signaling by binding to p300/CBP and displacing PCAF and p/CIP proteins from the complex. Here, we show that E1A directly represses the HAT activity of both p300/CBP and PCAF in vitro and p300-dependent transcription in vivo. Additionally, E1A inhibits nucleosomal histone modifications by the PCAF complex and blocks p53 acetylation. These results demonstrate the modulation of HAT activity as a novel mechanism of transcriptional regulation.
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Affiliation(s)
- D Chakravarti
- Gene Expression Laboratory, The Salk Institute for Biological Sciences, La Jolla, California 92037, USA
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14
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Kao HY, Ordentlich P, Koyano-Nakagawa N, Tang Z, Downes M, Kintner CR, Evans RM, Kadesch T. A histone deacetylase corepressor complex regulates the Notch signal transduction pathway. Genes Dev 1998; 12:2269-77. [PMID: 9694793 PMCID: PMC317043 DOI: 10.1101/gad.12.15.2269] [Citation(s) in RCA: 451] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/1998] [Accepted: 06/17/1998] [Indexed: 11/25/2022]
Abstract
The Delta-Notch signal transduction pathway has widespread roles in animal development in which it appears to control cell fate. CBF1/RBP-Jkappa, the mammalian homolog of Drosophila Suppressor of Hairless [Su(H)], switches from a transcriptional repressor to an activator upon Notch activation. The mechanism whereby Notch regulates this switch is not clear. In this report we show that prior to induction CBF1/RBP-Jkappa interacts with a corepressor complex containing SMRT (silencing mediator of retinoid and thyroid hormone receptors) and the histone deacetylase HDAC-1. This complex binds via the CBF1 repression domain, and mutants defective in repression fail to interact with the complex. Activation by Notch disrupts the formation of the repressor complex, thus establishing a molecular basis for the Notch switch. Finally, ESR-1, a Xenopus gene activated by Notch and X-Su(H), is induced in animal caps treated with TSA, an inhibitor of HDAC-1. The functional role for the SMRT/HDAC-1 complex in CBF1/RBP-Jkappa regulation reveals a novel genetic switch in which extracellular ligands control the status of critical nuclear cofactor complexes.
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Affiliation(s)
- H Y Kao
- Howard Hughes Medical Institute, The Salk Institute for Biological Studies, La Jolla, California 92037 USA
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Nagy L, Kao HY, Chakravarti D, Lin RJ, Hassig CA, Ayer DE, Schreiber SL, Evans RM. Nuclear receptor repression mediated by a complex containing SMRT, mSin3A, and histone deacetylase. Cell 1997; 89:373-80. [PMID: 9150137 DOI: 10.1016/s0092-8674(00)80218-4] [Citation(s) in RCA: 958] [Impact Index Per Article: 35.5] [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: 02/04/2023]
Abstract
The transcriptional corepressors SMRT and N-CoR function as silencing mediators for retinoid and thyroid hormone receptors. Here we show that SMRT and N-CoR directly interact with mSin3A, a corepressor for the Mad-Max heterodimer and a homolog of the yeast global-transcriptional repressor Sin3p. In addition, we demonstrate that the recently characterized histone deacetylase 1 (HDAC1) interacts with Sin3A and SMRT to form a multisubunit repressor complex. Consistent with this model, we find that HDAC inhibitors synergize with retinoic acid to stimulate hormone-responsive genes and differentiation of myeloid leukemia (HL-60) cells. This work establishes a convergence of repression pathways for bHLH-Zip proteins and nuclear receptors and suggests this type of regulation may be more widely conserved than previously suspected.
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Affiliation(s)
- L Nagy
- The Salk Institute for Biological Studies, La Jolla, California 92037, USA
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Kao HY, Siliciano PG. Identification of Prp40, a novel essential yeast splicing factor associated with the U1 small nuclear ribonucleoprotein particle. Mol Cell Biol 1996; 16:960-7. [PMID: 8622699 PMCID: PMC231078 DOI: 10.1128/mcb.16.3.960] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.8] [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: 01/31/2023] Open
Abstract
We have used suppressor genetics to identify factors that interact with Saccharomyces cerevisiae U1 small nuclear RNA (snRNA). In this way, we isolated PRP40-1, a suppressor that restores growth at 18 degrees C to a strain bearing a cold-sensitive mutation in U1 RNA. A gene disruption experiment shows that PRP40 is an essential gene. To study the role of PRP40 in splicing, we created a pool of temperature-sensitive prp40 strains. Primer extension analysis of intron-containing transcripts in prp40 temperature-sensitive strains reveals a splicing defect, indicating that Prp40 plays a direct role in pre-mRNA splicing. In addition, U1 RNA coimmunoprecipitates with Pro40, indicating that Prp40 is bound to the U1 small nuclear ribonucleoprotein particle in vivo. Therefore, we conclude that PRP40 encodes a novel, essential splicing component that associates with the yeast U1 small nuclear ribonucleoprotein particle.
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Affiliation(s)
- H Y Kao
- Department of Biochemistry and Institute of Human Genetics, University of Minnesota, Minneapolis, 55455, USA
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17
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Abstract
The Saccharomyces cerevisiae SNP1 gene encodes a protein that shares 30% amino acid identity with the mammalian U1 small nuclear ribonucleoprotein particle protein 70K (U1-70K). We have demonstrated that yeast strains in which the SNP1 gene was disrupted are viable but exhibit greatly increased doubling times and severe temperature sensitivity. Furthermore, snp1-null strains are defective in pre-mRNA splicing. We have tested deletion alleles of SNP1 for their ability to complement these phenotypes. We found that the highly conserved RNA recognition motif consensus domain of Snp1 is not required for complementation of the snp1-null growth or splicing defects nor for the in vivo association with the U1 small nuclear ribonucleoprotein particle. However, the amino-terminal domain of Snp1, less strongly conserved, is necessary and sufficient for complementation.
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Affiliation(s)
- P J Hilleren
- Department of Biochemistry, University of Minnesota, Minneapolis 55455, USA
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18
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Abstract
We have previously shown that the yeast PRP19 protein is a spliceosomal component, but is not tightly associated with small nuclear RNAs. It appears to associate with the spliceosome concomitant with or just after dissociation of the U4 small nuclear RNA during spliceosome assembly. We have found that PRP19 is associated with a protein complex in the splicing extract and that at least one of the associated components is essential for splicing. Taking advantage of the epitope tagging technique, we have isolated the PRP19-associated complex by affinity chromatography. The isolated complex is functional for complementation for the heat-inactivated prp19 mutant extract, and consists of at least seven polypeptides in addition to PRP19. At least three of these can interact directly with the PRP19 protein. We also show that the PRP19 protein itself is in an oligomeric form, which might be a prerequisite for its interaction with these proteins.
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Affiliation(s)
- W Y Tarn
- Institute of Molecular Biology, Academia Sinica, Nakang, Taipei, Taiwan, Republic of China
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19
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Abstract
The product of the yeast SNP1 gene has high homology to two domains of the metazoan U1 snRNP protein 70K, which binds to stem/loop I of the U1 RNA. However, the absence of other domains conserved in metazoan 70K and the minimal effect of yeast U1 RNA stem/loop I deletion make the assignment of SNP1 as yeast 70K less clear. To address this question, we have expressed the SNP1 gene as a fusion protein in E. coli and developed a gel shift assay for U1 RNA binding. We show here that the product of the yeast SNP1 gene binds directly and specifically to the first 47 nucleotides of yeast U1 RNA, which include the stem/loop 1 structure. We therefore conclude that the SNP1 gene product is the yeast 70K homolog. This is the first yeast protein to be identified as a homolog of a metazoan snRNP protein.
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Affiliation(s)
- H Y Kao
- Department of Biochemistry, University of Minnesota Medical School, Minneapolis 55455
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Wu YC, Lü YC, Kao HY, Pan CC, Lin RY. Cell-mediated immunity in patients with polychlorinated biphenyl poisoning. Taiwan Yi Xue Hui Za Zhi 1984; 83:419-29. [PMID: 6432941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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