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Xiao S, Chen C, Xia Q, Liu Y, Yao Y, Chen Q, Hartsfield M, Brozena A, Tu K, Eichhorn SJ, Yao Y, Li J, Gan W, Shi SQ, Yang VW, Lo Ricco M, Zhu JY, Burgert I, Luo A, Li T, Hu L. Lightweight, strong, moldable wood via cell wall engineering as a sustainable structural material. Science 2021; 374:465-471. [PMID: 34672741 DOI: 10.1126/science.abg9556] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Shaoliang Xiao
- Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA
| | - Chaoji Chen
- Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA
| | - Qinqin Xia
- Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA
| | - Yu Liu
- Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA
| | - Yuan Yao
- Center for Industrial Ecology, Yale School of the Environment, Yale University, New Haven, CT 06511, USA
| | - Qiongyu Chen
- Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA
| | - Matt Hartsfield
- Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - Alexandra Brozena
- Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA
| | - Kunkun Tu
- Wood Materials Science, Institute for Building Materials, ETH Zürich, 8093 Zürich, Switzerland.,WoodTec Group, Cellulose & Wood Materials, Empa, 8600 Dübendorf, Switzerland
| | - Stephen J Eichhorn
- Bristol Composites Institute, CAME School of Engineering, University of Bristol, University Walk, Bristol BS8 1TR, UK
| | - Yonggang Yao
- Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA
| | - Jianguo Li
- Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA
| | - Wentao Gan
- Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA
| | - Sheldon Q Shi
- Department of Mechanical Engineering, University of North Texas, Denton, TX 76203, USA
| | - Vina W Yang
- US Department of Agriculture (USDA) Forest Products Laboratory, Madison, WI 53726, USA
| | - Marco Lo Ricco
- US Department of Agriculture (USDA) Forest Products Laboratory, Madison, WI 53726, USA
| | - J Y Zhu
- US Department of Agriculture (USDA) Forest Products Laboratory, Madison, WI 53726, USA
| | - Ingo Burgert
- Wood Materials Science, Institute for Building Materials, ETH Zürich, 8093 Zürich, Switzerland.,WoodTec Group, Cellulose & Wood Materials, Empa, 8600 Dübendorf, Switzerland
| | - Alan Luo
- Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - Teng Li
- Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA
| | - Liangbing Hu
- Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA.,Center for Materials Innovation, University of Maryland, College Park, MD 20742, USA
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2
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Jung YH, Chang TH, Zhang H, Yao C, Zheng Q, Yang VW, Mi H, Kim M, Cho SJ, Park DW, Jiang H, Lee J, Qiu Y, Zhou W, Cai Z, Gong S, Ma Z. High-performance green flexible electronics based on biodegradable cellulose nanofibril paper. Nat Commun 2015; 6:7170. [PMID: 26006731 PMCID: PMC4455139 DOI: 10.1038/ncomms8170] [Citation(s) in RCA: 274] [Impact Index Per Article: 30.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 04/13/2015] [Indexed: 12/23/2022] Open
Abstract
Today's consumer electronics, such as cell phones, tablets and other portable electronic devices, are typically made of non-renewable, non-biodegradable, and sometimes potentially toxic (for example, gallium arsenide) materials. These consumer electronics are frequently upgraded or discarded, leading to serious environmental contamination. Thus, electronic systems consisting of renewable and biodegradable materials and minimal amount of potentially toxic materials are desirable. Here we report high-performance flexible microwave and digital electronics that consume the smallest amount of potentially toxic materials on biobased, biodegradable and flexible cellulose nanofibril papers. Furthermore, we demonstrate gallium arsenide microwave devices, the consumer wireless workhorse, in a transferrable thin-film form. Successful fabrication of key electrical components on the flexible cellulose nanofibril paper with comparable performance to their rigid counterparts and clear demonstration of fungal biodegradation of the cellulose-nanofibril-based electronics suggest that it is feasible to fabricate high-performance flexible electronics using ecofriendly materials.
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Affiliation(s)
- Yei Hwan Jung
- Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, 3445 Engineering Hall, Madison, Wisconsin 53706, USA
| | - Tzu-Hsuan Chang
- Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, 3445 Engineering Hall, Madison, Wisconsin 53706, USA
| | - Huilong Zhang
- Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, 3445 Engineering Hall, Madison, Wisconsin 53706, USA
| | - Chunhua Yao
- Department of Material Sciences and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Qifeng Zheng
- Department of Material Sciences and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Vina W Yang
- Forest Products Laboratory, USDA Forest Service, Madison, Wisconsin 53726, USA
| | - Hongyi Mi
- Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, 3445 Engineering Hall, Madison, Wisconsin 53706, USA
| | - Munho Kim
- Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, 3445 Engineering Hall, Madison, Wisconsin 53706, USA
| | - Sang June Cho
- Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, 3445 Engineering Hall, Madison, Wisconsin 53706, USA
| | - Dong-Wook Park
- Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, 3445 Engineering Hall, Madison, Wisconsin 53706, USA
| | - Hao Jiang
- Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, 3445 Engineering Hall, Madison, Wisconsin 53706, USA
| | - Juhwan Lee
- Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, 3445 Engineering Hall, Madison, Wisconsin 53706, USA
| | - Yijie Qiu
- 1] Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, 3445 Engineering Hall, Madison, Wisconsin 53706, USA [2] School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
| | - Weidong Zhou
- Department of Electrical Engineering, University of Texas-Arlington, Arlington, Texas 76019, USA
| | - Zhiyong Cai
- Forest Products Laboratory, USDA Forest Service, Madison, Wisconsin 53726, USA
| | - Shaoqin Gong
- 1] Department of Material Sciences and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA [2] Department of Biomedical Engineering and Wisconsin Institutes for Discovery, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Zhenqiang Ma
- Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, 3445 Engineering Hall, Madison, Wisconsin 53706, USA
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3
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Ghaleb AM, Katz JP, Kaestner KH, Du JX, Yang VW. Krüppel-like factor 4 exhibits antiapoptotic activity following gamma-radiation-induced DNA damage. Oncogene 2006; 26:2365-73. [PMID: 17016435 PMCID: PMC2230633 DOI: 10.1038/sj.onc.1210022] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
In response to gamma-radiation-induced DNA damage, organisms either activate cell cycle checkpoint and repair machinery or undergo apoptosis to eliminate damaged cells. Although previous studies indicated that the tumor suppressor p53 is critically involved in mediating both responses, how a cell decides which pathway to take is not well established. The zinc-finger-containing transcription factor, Krüppel-like factor 4 (KLF4), is a crucial mediator for the checkpoint functions of p53 after gamma-irradiation and does so by inhibiting the transition from the G(1) to S and G(2) to M phases of the cell cycle. Here, we determined the role of KLF4 in modulating the apoptotic response following gamma-irradiation. In three independent cell systems including colorectal cancer cells and mouse embryo fibroblasts in which expression of KLF4 could be manipulated, we observed that gamma-irradiated cells underwent apoptosis if KLF4 was absent. In the presence of KLF4, the degree of apoptosis was significantly reduced and cells resorted to checkpoint arrest. The mechanism by which KLF4 accomplished this antiapoptotic effect is by activating expression of the cell cycle arrest gene, p21(WAF1/CIP1), and by inhibiting the ability of p53 to transactivate expression of the proapoptotic gene, BAX. Results of our study illustrate an unexpected antiapoptotic function of KLF4, heretofore considered a tumor suppressor in colorectal cancer, and suggest that KLF4 may be an important determinant of cell fate following gamma-radiation-induced DNA damage.
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Affiliation(s)
- AM Ghaleb
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA
| | - JP Katz
- Division of Gastroenterology, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
| | - KH Kaestner
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
| | - JX Du
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA
| | - VW Yang
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA
- Department of Hematology and Oncology, Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, USA
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4
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Geiman DE, Ton-That H, Johnson JM, Yang VW. Transactivation and growth suppression by the gut-enriched Krüppel-like factor (Krüppel-like factor 4) are dependent on acidic amino acid residues and protein-protein interaction. Nucleic Acids Res 2000; 28:1106-13. [PMID: 10666450 PMCID: PMC102607 DOI: 10.1093/nar/28.5.1106] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.3] [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: 12/30/2022] Open
Abstract
Gut-enriched Krüppel-like factor (GKLF or KLF4) is a pleiotropic (activating and repressive) transcription factor. This study characterizes the mechanisms of transactivation by GKLF. Using a GAL4 fusion assay, the activating domain of murine GKLF was localized to the 109 amino acid residues in the N-terminus. Site-directed mutagenesis showed that two adjacent clusters of acidic residues within this region are responsible for the activating effect. Transactivation by GKLF involves intermolecular interactions as demonstrated by the ability of wild-type, but not mutated, GKLF to compete with the N-terminal activation domain. In addition, wild-type adenovirus E1A, but not a mutated E1A that failed to bind p300/CBP, inhibited transactivation by the N-terminal 109 amino acids of GKLF, suggesting that p300/CBP are GKLF's interacting partners. A physical interaction between GKLF and CBP was demonstrated by glutathione- S -transferase pull-down and by in vivo co-immuno-precipitation experiments. We also showed that the two acidic amino acid clusters are essential for this interaction, since GKLF with mutations in these residues failed to co-immunoprecipitate with CBP. Importantly, the same mutations abrogated the ability of GKLF to suppress cell growth as determined by a colony suppression assay. These studies therefore provide plausible evidence for a structural and functional correlation between the transactivating and growth-suppressing effects of GKLF.
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Affiliation(s)
- D E Geiman
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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5
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Yang VW, Geiman DE, Hubbard WC, Spannhake EW, Hylind LM, Hamilton SR, Giardiello FM. Tissue prostanoids as biomarkers for chemoprevention of colorectal neoplasia: correlation between prostanoid synthesis and clinical response in familial adenomatous polyposis. Prostaglandins Other Lipid Mediat 2000; 60:83-96. [PMID: 10680778 PMCID: PMC2714803 DOI: 10.1016/s0090-6980(99)00054-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [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] [Indexed: 11/21/2022]
Abstract
Recent studies indicate that sulindac, a nonsteroidal anti-inflammatory drug (NSAID), lowers mucosal prostanoid levels and regresses colorectal adenomas in patients with familial adenomatous polyposis (FAP). To determine whether they are biomarkers for sulindac-mediated chemoprevention of colorectal adenomas, levels of 5 prostanoids [prostaglandin (PG) D2, PGE2, PGF2alpha, thromboxane B2, and 6-keto-PGF1alpha] in the normal-appearing rectal mucosa from 7 FAP patients with a history of subtotal colectomy and ileorectal anastomosis and 4 FAP patients without surgery, were measured in the absence or presence of exogenously added arachidonic acid before the initiation and at the end of 3 months of sulindac treatment. The addition of arachidonic acid resulted in a uniform increase in the levels of all 5 prostanoids although this increase was selectively attenuated in patients with ileorectal anastomosis who took sulindac. In the latter patients, arachidonic acid also augmented the inhibition of prostanoid synthesis by sulindac. In contrast, sulindac failed to attenuate the increase in prostanoid levels resulting from arachidonic acid in patients without previous surgery. Importantly, when measured in the presence of arachidonic acid, the reduction in the levels of all 5 prostanoids due to sulindac was statistically correlated with a reduction in the size and number of adenomas in the two groups of patients combined. These results suggest that tissue prostanoids measured in the presence of arachidonic acid may serve as sensitive and reliable biomarkers in monitoring the clinical responsiveness of FAP patients undergoing chemoprevention for colorectal neoplasia with NSAIDs.
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Affiliation(s)
- V W Yang
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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6
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Mahatan CS, Kaestner KH, Geiman DE, Yang VW. Characterization of the structure and regulation of the murine gene encoding gut-enriched Krüppel-like factor (Krüppel-like factor 4). Nucleic Acids Res 1999; 27:4562-9. [PMID: 10556311 PMCID: PMC148743 DOI: 10.1093/nar/27.23.4562] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.5] [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: 11/12/2022] Open
Abstract
Gut-enriched Krüppel-like factor (GKLF, KLF4) is an epithelial-specific transcription factor whose expression is associated with growth arrest. In order to understand the mechanisms regulating expression of the gene encoding GKLF, we isolated a genomic clone containing murine GKLF. The gene spans 5.3 kb and contains four exons. A major start site of transcription was mapped to an adenine residue 601 nt 5' of the translation initiation codon. An additional 1 kb of the 5'-flanking region was sequenced and found to contain multiple cis -elements homologous to the binding sites of several established transcription factors including Sp1, AP-1, Cdx, GATA, and USF. In particular, three closely spaced GC-boxes 5' of the TATA box resemble the established binding site for GKLF. DNase I protection and electrophoretic mobility shift assays verified that recombinant GKLF bound to each of the three GC-boxes. In co-transfection experiments, GKLF transactivated a reporter gene linked to the GKLF 1 kb 5'-flanking region, as did Sp1, Sp3 and Cdx-2. Mutations of one or both of the first and second GC-boxes in the promoter resulted in diminished transactivation by GKLF. These results demonstrate that the 5'-flanking sequence of the mouse GKLF gene functions as a promoter and is subject to autoregulation by its own gene product.
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Affiliation(s)
- C S Mahatan
- Department of Medicine, The Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
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7
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Abstract
Colorectal cancer is a major cause of morbidity and mortality among types of cancer in the United States. Significant progress has been made in understanding the molecular mechanisms that lead to it. Much knowledge was obtained through study of genetic changes that occur in individuals with a familial predisposition to colorectal cancer, including familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC) syndromes. The gene with mutations that result in FAP has been identified as adenomatous polyposis coli (APC). Similarly, mutations in several genes that normally function in DNA mismatch repair result in HNPCC. Colorectal cancer is the result of accumulated mutations in several additional oncogenes or tumor suppressor genes, and this information leads to the formulation of a genetic model for the disease. Recent studies have also identified a relatively prevalent polymorphism in the APC gene in Ashkenazi Jews that is associated with an increased risk for colorectal cancer. These studies present a paradigm based on the APC mutation (APC I1307K) for the screening of cancer susceptibility genes in the population at large. Currently available techniques for genetic testing of colorectal cancer are also discussed in this review, along with their ethical implications.
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Affiliation(s)
- V W Yang
- Division of Gastroenterology, Department of Medicine, The Johns Hopkins University School of Medicine, Ross 918, 720 Rutland Avenue, Baltimore, MD 21205, USA
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8
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Rich RL, Deivanayagam CC, Owens RT, Carson M, Höök A, Moore D, Symersky J, Yang VW, Narayana SV, Höök M. Trench-shaped binding sites promote multiple classes of interactions between collagen and the adherence receptors, alpha(1)beta(1) integrin and Staphylococcus aureus cna MSCRAMM. J Biol Chem 1999; 274:24906-13. [PMID: 10455165 DOI: 10.1074/jbc.274.35.24906] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.3] [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: 11/06/2022] Open
Abstract
Most mammalian cells and some pathogenic bacteria are capable of adhering to collagenous substrates in processes mediated by specific cell surface adherence molecules. Crystal structures of collagen-binding regions of the human integrin alpha(2)beta(1) and a Staphylococcus aureus adhesin reveal a "trench" on the surface of both of these proteins. This trench can accommodate a collagen triple-helical structure and presumably represents the ligand-binding site (Emsley, J., King, S. L., Bergelson, J. M., and Liddington, R. C. (1997) J. Biol. Chem. 272, 28512-28517; Symersky, J., Patti, J. M., Carson, M., House-Pompeo, K., Teale, M., Moore, D., Jin, L., Schneider, A., DeLucas, L. J., Höök, M., and Narayana, S. V. L. (1997) Nat. Struct. Biol. 4, 833-838). We report here the crystal structure of the alpha subunit I domain from the alpha(1)beta(1) integrin. This collagen-binding protein also contains a trench on one face in which the collagen triple helix may be docked. Furthermore, we compare the collagen-binding mechanisms of the human alpha(1) integrin I domain and the A domain from the S. aureus collagen adhesin, Cna. Although the S. aureus and human proteins have unrelated amino acid sequences, secondary structure composition, and cation requirements for effective ligand binding, both proteins bind at multiple sites within one collagen molecule, with the sites in collagen varying in their affinity for the adherence molecule. We propose that (i) these evolutionarily dissimilar adherence proteins recognize collagen via similar mechanisms, (ii) the multisite, multiclass protein/ligand interactions observed in these two systems result from a binding-site trench, and (iii) this unusual binding mechanism may be thematic for proteins binding extended, rigid ligands that contain repeating structural motifs.
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Affiliation(s)
- R L Rich
- Center for Extracellular Matrix Biology, Institute of Biosciences and Technology, Texas A&M University, Houston, Texas 77030, USA.
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9
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Abstract
Decorin is ubiquitously distributed in the extracellular matrix of mammals and a member of the proteoglycan family characterized by a core protein dominated by leucine-rich repeat motifs. We show here that decorin extracted from bovine tissues under denaturing conditions or produced in recombinant "native" form by cultured mammalian cells has a high affinity for Zn2+ as demonstrated by equilibrium dialyses. The Zn2+-binding sites are localized to the N-terminal domain of the core protein that contains 4 Cys residues in a spacing reminiscent of a zinc finger. A recombinant 41-amino acid long peptide representing the N-terminal domain of decorin has full Zn2+ binding activity and binds two Zn2+ ions with an average KD of 3 x 10(-7) M. Binding of Zn2+ to this peptide results in a change in secondary structure as shown by circular dichroism spectroscopy. Biglycan, a proteoglycan that is structurally closely related to decorin contains a similar high affinity Zn2+-binding segment, whereas the structurally more distantly related proteoglycans, epiphycan and osteoglycin, do not bind Zn2+ with high affinity.
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Affiliation(s)
- V W Yang
- Graduate School of Biomedical Sciences, University of Texas, Houston Health Science Center, Houston, Texas 77030, USA
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10
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Affiliation(s)
- V W Yang
- Departments of Medicine and Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Yang VW, Shields JM, Hamilton SR, Spannhake EW, Hubbard WC, Hylind LM, Robinson CR, Giardiello FM. Size-dependent increase in prostanoid levels in adenomas of patients with familial adenomatous polyposis. Cancer Res 1998; 58:1750-3. [PMID: 9563494] [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] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Recent studies indicate that nonsteroidal anti-inflammatory drugs have a chemopreventive effect against colorectal neoplasia. Nonsteroidal anti-inflammatory drugs inhibit cyclooxygenases, principal enzymes that mediate the formation of prostanoids. To determine whether prostanoids are involved in the pathogenesis of colorectal adenomas, we compared the levels of five major stable metabolic products of the cyclooxygenase pathway in the normal-appearing mucosa and in adenomas of patients with familial adenomatosis polyposis. Of 12 patients tested, 6 had elevated levels of at least one prostanoid in the adenomas. More importantly, the relative levels of three prostanoids [prostaglandin (PG)D2, PGE2, and 6-keto-PGF1alpha] were elevated in adenomas compared to normal-appearing mucosa from the same patients, and the resulting ratios were correlated with the size of the adenoma. These results suggest a role for prostanoids in progression of colorectal polyposis in familial adenomatosis polyposis patients.
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Affiliation(s)
- V W Yang
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
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12
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Giardiello FM, Spannhake EW, DuBois RN, Hylind LM, Robinson CR, Hubbard WC, Hamilton SR, Yang VW. Prostaglandin levels in human colorectal mucosa: effects of sulindac in patients with familial adenomatous polyposis. Dig Dis Sci 1998; 43:311-6. [PMID: 9512123 PMCID: PMC2700288 DOI: 10.1023/a:1018898120673] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Recent evidence suggests that nonsteroidal antiinflammatory drugs (NSAIDs) may prevent colorectal cancer. The mechanism of action of NSAIDs in chemoprevention is unknown but may be linked to their effect on mucosal prostaglandin levels. Levels of five major prostaglandin metabolites were measured by gas chromatography-mass spectrometry in biopsy specimens of flat rectal mucosa from four patients with familial adenomatous polyposis (FAP) before and after sulindac therapy and from five healthy individuals. The prostaglandin present at highest concentration in rectal mucosa from FAP and control subjects was prostaglandin E2. The concentration of thromboxane B2 alone was significantly elevated in FAP patients compared to controls (P = 0.016). In FAP patients treated with sulindac, all prostaglandin metabolite levels were significantly reduced compared to pretreatment levels (P < 0.05) except prostaglandin D2 (P = 0.07). Prostaglandins D2, E2, F2alpha, and 6-keto-F1alpha levels also were significantly reduced in FAP patients on sulindac compared to healthy controls (P < 0.05). However, interpatient heterogeneity of response to sulindac was evident with changes ranging from +19% to -89%, and the patient with the greatest reductions after sulindac developed colorectal cancer after 35 months of therapy. Sulindac treatment, at drug doses shown to regress colorectal adenomas in FAP patients, has heterogeneous effects on the level of major prostaglandins in their rectal mucosa and may not prevent colorectal cancer due to uncoupling of prostaglandin levels and carcinogenesis.
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Affiliation(s)
- F M Giardiello
- Department of Medicine, Oncology Center, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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13
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Abstract
The gut-enriched Krüppel-like factor (GKLF) is a recently identified eukaryotic transcription factor that contains three C2H2zinc fingers. The amino acid sequence of the zinc finger portion of GKLF is closely related to several Krüppel proteins, including the lung Krüppel-like factor (LKLF), the erythroid Krüppel-like factor (EKLF) and the basic transcription element binding protein 2 (BTEB2). The DNA sequence to which GKLF binds has not been definitively established. In the present study we determined the DNA binding sequence of GKLF using highly purified recombinant GKLF in a target detection assay of an oligonucleotide library consisting of random sequences. Upon repeated rounds of selection and subsequent characterization of the selected sequences by base-specific mutagenesis a DNA with the sequence 5'-G/AG/AGGC/TGC/T-3' was found to contain the minimal essential binding site for GKLF. This sequence is present in the promoters of two previously characterized genes: the CACCC element of the beta-globin gene, which interacts with EKLF, and the basic transcription element (BTE) of the CYP1A1 gene, which interacts with Sp1 and several Sp1-like transcription factors. Moreover, the selected GKLF binding sequence was capable of mediating transactivation of a linked reporter gene by GKLF in co-transfection experiments. Our results establish GKLF as a sequence-specific transcription factor likely involved in regulation of expression of endogenous genes.
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Affiliation(s)
- J M Shields
- Department of Medicine and Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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14
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Abstract
This research examined the titers of hexokinase (HK), phosphofructokinase (PFK), and xylulokinase (XUK) in Saccharomyces cerevisiae and two xylose fermenting yeasts, Pachysolen tannophilus and Candida shehatae, following shifts in carbon source and aeration. Xylose-grown C. shehatae, glucose-grown P. tannophilus, and glucose-grown S. cerevisiae, had the highest specific activities of XUK, HK, and PFK, respectively. XUK was induced by xylose to moderate levels in both P. tannophilus and C. shehatae, but was present only in trace levels in S. cerevisiae. HK activities in P. tannophilus were two to three fold higher when cells were grown on glucose than when grown on xylose, but HK levels were less inducible in C. shehatae. The PFK activities in S. cerevisiae were 1.5 to 2 times higher than in the two xylose-fermenting yeasts. Transfer from glucose to xylose rapidly inactivated HK in P. tannophilus, and transfer from xylose to glucose inactivated XUK in C. shehatae. The patterns of induction and inactivation indicate that the basic regulatory mechanisms differ in the two xylose fermenting yeasts.
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Affiliation(s)
- V W Yang
- Institute for Microbial and Biochemical Technology, Forest Products Laboratory, Madison, WI 53705-2398, USA
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15
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Breitwieser GE, McLenithan JC, Cortese JF, Shields JM, Oliva MM, Majewski JL, Machamer CE, Yang VW. Colonic epithelium-enriched protein A4 is a proteolipid that exhibits ion channel characteristics. Am J Physiol 1997; 272:C957-65. [PMID: 9124532 DOI: 10.1152/ajpcell.1997.272.3.c957] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Expression of the human gene A4 is enriched in the colonic epithelium and is transcriptionally activated on differentiation of colonic epithelial cells in vitro (M. M. Oliva, T. C. Wu, and V. W. Yang. Arch. Biochem. Biophys. 302: 183-192, 1993). A4 cDNA contains an open reading frame that predicts a polypeptide of 17 kDa. To determine the function of the A4 protein, we characterized its biochemical and physiological properties. Hydropathy analysis of deduced A4 amino acid sequence revealed four putative membrane-spanning alpha-helices. The hydrophobic nature of A4 was confirmed by its being extractable with organic solvents. Immunocytochemical studies of cells expressing A4 localized it to the endoplasmic reticulum. Moreover, A4 multimerized in vivo as determined by coimmunoprecipitation experiments. The four-transmembrane topology and biophysical characteristics of A4 suggest that it belongs to a family of integral membrane proteins called proteolipids, some of which multimerize to form ion channels. Subsequent electrophysiological studies of nuclei isolated from microinjected Xenopus laevis oocytes transiently expressing A4 showed the appearance of a 28-pS channel. Thus our studies indicate that A4 is a colonic epithelium-enriched protein localized to the endoplasmic reticulum and that, similar to other proteolipids, A4 multimerizes and exhibits characteristics of an ion channel.
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Affiliation(s)
- G E Breitwieser
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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16
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Giardiello FM, Hamilton SR, Hylind LM, Yang VW, Tamez P, Casero RA. Ornithine decarboxylase and polyamines in familial adenomatous polyposis. Cancer Res 1997; 57:199-201. [PMID: 9000553] [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] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Familial adenomatous polyposis (FAP), due to germ-line mutation of the adenomatous polyposis coli (APC) gene, is characterized by development of colorectal adenomas and ultimately colorectal cancer. The usefulness of ornithine decarboxylase (ODC) activity and polyamine levels in normal-appearing colorectal mucosa to stratify risk for colorectal neoplasia by discriminating presymptomatic individuals with germ-line APC mutation (genotype-positive) from genotype-negative family controls was evaluated in 36 at-risk subjects undergoing endoscopic and genetic screening for FAP. ODC activity and levels of putrescine, spermidine, and spermine were significantly higher in presymptomatic genotype-positive patients compared to genotype-negative persons (P = 0.029, <0.001, 0.002, and <0.001, respectively). Moreover, a putrescine level with a cutoff point of 1.5 nmol/mg protein was the most accurate single discriminator of risk status. ODC activity and polyamine levels are significantly elevated in gene carriers of FAP before the development of polyposis, suggesting a role for these compounds in tumorigenesis of FAP. These assays may be useful in evaluating at-risk members of FAP families in which mutation of the APC gene cannot be found.
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Affiliation(s)
- F M Giardiello
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA
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17
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Abstract
IBD is a disease of unknown cause that involves an amplification of the inflammatory response in the intestinal mucosa. Although not the only offending agents leading to the disease, eicosanoids, the collective group of AA metabolites, may a significant role in the pathogenesis of IBD. This article reviewed the biochemical pathways of eicosanoid formation and the clinical relevance of eicosanoids to IBD. Potential strategies designed to interfere with various aspects of AA metabolism were also outlined. Further clinical trials of newer compounds may soon prove them effective in the management of IBD.
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Affiliation(s)
- V W Yang
- Department of Medicine, Johns Hopkins School of Medicine, Baltimore, MD, USA
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18
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19
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Abstract
Expression of the class I alcohol dehydrogenase (ADH) gene in the rat hepatoma microcell hybrid cell line, 11-3, was examined. The steady-state level of ADH mRNA in 11-3 was approximately 2-fold higher than that or rat liver and Fao, the parental cell line of 11-3. Removal of steroid hormones by activated charcoal from the serum in which 11-3 cells were maintained resulted in a significant decrease in the level of ADH transcript. Dexamethasone at a concentration of 1 muM increased the ADH mRNA content in 11-3 in a time-dependent fashion, up to 48 hr after its addition to cells that had first been deprived of steroid hormones. In addition, levels of ADH transcript in cells treated with dexamethasone increased in a dose-dependent manner, and the concentration of dexamethasone required to achieve half-maximal activation was 5 nM. By using the techniques of reverse transcription and polymerase chain reaction, and by taking advantage of a restriction polymorphism present between the rat and mouse ADH cDNA, we found that 11-3 contained both the rat and mouse class I ADH transcripts, although the rat sequence accounted for the great majority. Moreover, levels of both rat and mouse class I ADH transcripts increased in a similarly time-dependent manner in cells treated with dexamethasone. These results indicate that expression of class I ADH gene in 11-3 is high and is regulated by glucocorticoids, making the cell line an excellent model for the in vitro study of ADH expression.
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Affiliation(s)
- J L Majewski
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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20
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Yang VW, Zhuang Z, Elegir G, Jeffries TW. Alkaline-active xylanase produced by an alkaliphilicBacillus sp isolated from kraft pulp. ACTA ACUST UNITED AC 1995. [DOI: 10.1007/bf01569971] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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21
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Abstract
Gene A4 is transcriptionally activated upon enterocyte differentiation of the human colonic epithelial cell line HT29-18 and its highly differentiated subclone HT29-18-C1 [Oliva et al., Arch. Biochem. Biophys. 302 (1993) 183-192]. To characterize the mechanisms regulating the differential transcription of A4, we analyzed its immediate 5'-flanking region for regulatory elements. Promoter-linked transfection experiments of progressively deleted A4 5'-flanking sequences fused to the bacterial cat reporter gene suggest the presence of one negative and two positive DNA elements within the first 371 bp of the A4 promoter (pA4). DNase I footprint and electrophoretic mobility shift assays demonstrate that one positive element which contains the core binding sequence for the transcription factor, Sp1, mediates an equal level of transcription in the two cell types. The second positive element, localized between nucleotide positions--169 and -152, contains a sequence previously unrecognized as a transcription factor-binding site. This element mediates a twofold increase in the activity of pA4 in HT29-18-C1, as compared to HT29-18. Furthermore, nuclear extracts obtained from HT29-18-C1 contain a higher binding activity for this element than those from HT29-18. Southwestern blot analysis suggests that the protein interacting with this element has an estimated molecular mass of 50 kDa. We conclude that this protein may be involved in the differential regulation of A4 in these intestinal cell lines.
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Affiliation(s)
- M M Oliva
- Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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22
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Abstract
Leukotrienes (LTs), the 5-lipoxygenase (5-LOX) metabolites of arachidonic acid, have roles in many biological processes relevant to the gastrointestinal tract, including intestinal inflammation. We screened two well-known human intestinal epithelial cell lines, HT29 and Caco-2, for evidence of LT-associated enzyme transcripts and LT synthesis. Northern blot analysis of total RNA from both intestinal lines demonstrated high levels of transcripts for LTA4 hydrolase, a multisubstrate enzyme that converts the 5-LOX metabolite, LTA4, to LTB4. With total RNA, the 5-LOX transcript was detected only in HT29. Caco-2 failed to show 5-LOX message even with poly A-containing RNA, although the transcript could be amplified with the polymerase chain reaction. Messenger RNA for FLAP, the 5-lipoxygenase-activating protein, was detectable in both cell lines, but only with poly A-containing RNA. In a sonicated cell preparation, HT29, but not Caco-2, revealed detectable levels of 5-HETE and LTB4. These results suggest that certain intestinal epithelial cells possess a limited capacity to synthesize LTs.
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Affiliation(s)
- J F Cortese
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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23
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Yang VW, Marks JA, Davis BP, Jeffries TW. High-efficiency transformation of Pichia stipitis based on its URA3 gene and a homologous autonomous replication sequence, ARS2. Appl Environ Microbiol 1994; 60:4245-54. [PMID: 7811063 PMCID: PMC201976 DOI: 10.1128/aem.60.12.4245-4254.1994] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.5] [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] Open
Abstract
This paper describes the first high-efficiency transformation system for the xylose-fermenting yeast Pichia stipitis. The system includes integrating and autonomously replicating plasmids based on the gene for orotidine-5'-phosphate decarboxylase (URA3) and an autonomous replicating sequence (ARS) element (ARS2) isolated from P. stipitis CBS 6054. Ura- auxotrophs were obtained by selecting for resistance to 5-fluoroorotic acid and were identified as ura3 mutants by transformation with P. stipitis URA3. P. stipitis URA3 was cloned by its homology to Saccharomyces cerevisiae URA3, with which it is 69% identical in the coding region. P. stipitis ARS elements were cloned functionally through plasmid rescue. These sequences confer autonomous replication when cloned into vectors bearing the P. stipitis URA3 gene. P. stipitis ARS2 has features similar to those of the consensus ARS of S. cerevisiae and other ARS elements. Circular plasmids bearing the P. stipitis URA3 gene with various amounts of flanking sequences produced 600 to 8,600 Ura+ transformants per micrograms of DNA by electroporation. Most transformants obtained with circular vectors arose without integration of vector sequences. One vector yielded 5,200 to 12,500 Ura+ transformants per micrograms of DNA after it was linearized at various restriction enzyme sites within the P. stipitis URA3 insert. Transformants arising from linearized vectors produced stable integrants, and integration events were site specific for the genomic ura3 in 20% of the transformants examined. Plasmids bearing the P. stipitis URA3 gene and ARS2 element produced more than 30,000 transformants per micrograms of plasmid DNA. Autonomously replicating plasmids were stable for at least 50 generations in selection medium and were present at an average of 10 copies per nucleus.
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Affiliation(s)
- V W Yang
- Forest Products Laboratory, U.S. Department of Agriculture, Madison, Wisconsin 53705
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24
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Potter JJ, Mezey E, Yang VW. The adult enhancer factor-1, a Drosophila melanogaster transcriptional repressor, modulates the promoter activity of the rat class-I alcohol dehydrogenase-encoding gene. Gene X 1994; 149:325-30. [PMID: 7959011 DOI: 10.1016/0378-1119(94)90170-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [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: 01/28/2023] Open
Abstract
Expression of the Drosophila melanogaster alcohol dehydrogenase-encoding gene (ADH) in the adult fat body is controlled by the ADH adult enhancer site (AAE). The D. melanogaster transcription repressor, adult enhancer factor-1 (AEF-1), binds to AAE at a site which overlaps with a sequence recognized by the mammalian transcription factor, CCAAT/enhancer-binding protein alpha [C/EBP alpha; Falb and Maniatis, Genes Dev. 6 (1992a) 454-465]. C/EBP alpha also activates the promoter of the rat class-I ADH gene in a sequence-specific manner [Potter et al., Arch. Biochem. Biophys. 285 (1991a) 246-251]. In this study, we explored the possibility that D. melanogaster AEF-1 influences transcription of the rat class-I ADH. By DNase I footprint analysis, bacterially produced AEF-1 protects a region of DNA between nucleotides (nt) -22 and -36 of the rat class-I ADH promoter (pADH), just 5' to the binding site of C/EBP alpha, a result confirmed by the electrophoretic mobility shift assay (EMSA). Co-transfection of a rat pADH-CAT reporter construct with expression vectors containing C/EBP alpha, AEF-1, or both, indicates that AEF-1 inhibits induction of the rat pADH by C/EBP alpha. Moreover, rat liver nuclear extracts appear to contain AEF-1-like-binding activities to AAE by EMSA. These experiments suggest an evolutionarily conserved mechanism by which AEF-1 modulates expression of the D. melanogaster and rat ADH genes.
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Affiliation(s)
- J J Potter
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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Cortese JF, Majewski JL, Crabb DW, Edenberg HJ, Yang VW. Characterization of the 5'-flanking sequence of rat class I alcohol dehydrogenase gene. J Biol Chem 1994; 269:21898-906. [PMID: 8063834] [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] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Expression of the rat class I alcohol dehydrogenase (ADH) gene is highest in the liver and regions of the intestine. We characterized over 3 kilobases of the gene's 5'-flanking region by sequencing and transient transfection. Alignment of the flanking sequence of the rat gene with those of the mouse and human class I genes revealed a cis-acting element, known to be a functional glucocorticoid response element in the human gene and conserved in the mouse, is interrupted in the rat promoter by a 490-base pair processed retropseudogene of the ribosomal protein S25. Southern analysis indicated that this inserted element is present in the class I ADH promoters of multiple strains of rat. Transfection analysis of the rat and mouse promoters showed that the mouse, but not the rat promoter, is inducible by dexamethasone. Electrophoretic mobility shift assays using nuclear extracts from dexamethasone-treated cells confirmed that the mouse's element interacts with the glucocorticoid receptor. Transient transfection of the 5'-flanking region of the rat gene linked to a human growth hormone reporter demonstrated the liver and intestinal specificity of the rat promoter. Two positive elements, one from nucleotides -1,327 to -977 and the other from -241 to -12, were shown to support high levels of reporter activity. In addition, a suppressive element was localized between nucleotides -403 and -241, a region of DNA situated within the domain of the S25 ribosomal protein pseudogene.
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Affiliation(s)
- J F Cortese
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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26
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Abstract
Class I alcohol dehydrogenase (ADH) is the principal enzyme responsible for ethanol oxidation in mammals. Although primarily regarded as an enzyme that functions in the adult, Class I ADH has been reported to be present in fetal tissues. By in situ hybridization, we demonstrated the tissue localization of the Class I ADH transcript in developing rat fetuses between Days 15 (E15) and 18 (E18) of gestation. Abundant transcripts were present in epidermis, lung, and urinary bladder. In these tissues, the messages were localized primarily to the superficial layer of the epithelium and increased with development. The liver exhibited significant signals only in the E18 fetus, when parenchymal hepatocytes first appeared. The E15 and E16 small intestines, with their epithelium arranged in a stratified fashion, displayed signals in the submucosal mesenchymal layer. By E17, a rearrangement of the intestinal epithelium into an almost monolayer configuration was observed. This change was associated with a redistribution of the ADH transcript to the surface of the epithelium. Further relocation of the messages was noted in the adult small intestine, in which they became concentrated in the base of the crypt. These findings indicate that expression of the rat class I ADH gene follows a dynamic course in specific epithelial tissues during fetal development. In addition, the apparent superficial localization of the ADH message in most of these tissues suggests that ADH functions in metabolizing either endogenously or exogenously derived alcohol substrates present in the fetal environment.
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Affiliation(s)
- T G Tietjen
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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27
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Abstract
The mammalian class I alcohol dehydrogenase is the principal enzyme responsible for ethanol metabolism. While it is regarded primarily as a liver-specific enzyme, class I alcohol dehydrogenase is known to be present in a number of extrahepatic tissues. The purpose of the current study is to define the tissue and cellular distribution of the dehydrogenase transcript in four rat tissues previously shown to contain high levels of mRNA: the liver, the proximal small intestine, the colon and the testis. Localization of the transcript was examined in formalin-fixed, paraffin-embedded rat tissues by in situ hybridization using radioactively labelled antisense rat alcohol dehydrogenase RNA probe. In the liver, the dehydrogenase message is localized primarily to the perivenous hepatocytes. In the proximal small intestine and the colon, the message follows a vertical gradient of distribution along the crypt-villus and the crypt-surface epithelium axes, respectively, with the base of the crypt exhibiting the greatest concentration. In the testis, the message is localized primarily to cells in the interstitium. These findings illustrate a highly compartmentalized nature of distribution of the class I alcohol dehydrogenase transcript in the tissues studied and may help to elucidate the metabolic functions of this enzyme in these tissues.
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Affiliation(s)
- T G Tietjen
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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28
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Abstract
The human colonic epithelial cell line HT29, and its clonal derivatives HT29-18 and HT-29-18-C1, differentiate in vitro. Differential screening of a subtraction cDNA library enriched for sequences unique to HT29-18-C1, a highly differentiated subclone of HT29-18, resulted in the isolation of a differentiation-dependent cDNA clone, A4. A full-length clone encoding A4 was obtained and sequenced to its entirety. It is 945 bp in length and contains an open reading frame (ORF) of 456 bp. The amino acid sequence deduced from the ORF reveals a polypeptide of 152 amino acids with a predicted molecular mass of 17,000 Da, a size confirmed by coupled in vitro transcription and translation directed by the full-length A4 cDNA. This polypeptide contains four potential membrane-spanning domains and consensus sequences for N-linked glycosylation as well as phosphorylation sites for protein kinase C and casein kinase II. Comparison of A4 to published DNA and protein sequences revealed no significant homology. Genomic Southern blot analysis suggests that the gene is present in a single copy within the human genome and is conserved in the rat. Northern blot analysis of RNA obtained from various rat tissues shows that the expression of the A4 gene is tissue-selective and is enriched in colonic mucosa. In situ hybridization using human intestinal tissues indicates that the expression of A4 follows a gradient along the crypt-to-villus axis with the most abundant message occurring in the lower half of the crypt. Furthermore, nuclear run-on assays suggest that the induction of the A4 gene during differentiation of HT29-18 is regulated at a transcriptional level. A clone was isolated from a human genomic library and found to contain all five exons of A4. S1 nuclease analysis localized the start site of transcription to an adenosine residue 91 nucleotides upstream from the ATG translation initiation codon. Examination of the immediate sequence 5' to the mRNA start site reveals no TATA box and multiple known enhancer sequences. A4 is also noted to share certain features with the gene encoding the cystic fibrosis transmembrane conductance regulator protein. They include a similar vertical distribution of expression along the intestinal epithelium, enhanced transcription upon differentiation of HT29-18, and multiple shared putative regulatory sequences in the promoter regions. Further characterization of the mechanisms regulating expression of the A4 gene could contribute to the understanding of mammalian intestinal differentiation.
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Affiliation(s)
- M M Oliva
- Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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29
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Abstract
Growth hormone (GH) increases the transcription of the rat class I alcohol dehydrogenase (ADH) gene. Two transcription factors, the CCAAT/enhancer binding protein (C/EBP) and the liver activator protein (LAP), were previously shown to bind to the ADH promoter at nucleotide positions -11 to -22 relative to the start-site of transcription and to activate the ADH promoter in co-transfection experiments. In this study, exposure of cultured rat hepatocytes to GH (1 micrograms/ml) for 4 days increased LAP mRNA, but not C/EBP mRNA, in conjunction with an increase in ADH mRNA. GH, in transient transfection experiments of primary rat hepatocyte cultures, activated an ADH promoter-reporter gene construct containing the C/EBP binding site, but failed to activate a construct containing a 4-bp mutation at this site. These results suggest that the effect of GH in enhancing ADH promoter activity is mediated by LAP binding to the C/EBP site.
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Affiliation(s)
- J J Potter
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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30
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Canto MF, Oliva MM, Potter JJ, Mezey E, Yang VW. Enhancer-site downstream binding protein activity is enriched in rat tissues that express the class I alcohol dehydrogenase gene. Biochem Biophys Res Commun 1992; 188:684-9. [PMID: 1280119 DOI: 10.1016/0006-291x(92)91110-c] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The activity of the rat class I alcohol dehydrogenase (ADH) is enriched in certain tissues including the liver, intestine and testis. The tissue-specific expression of the gene encoding ADH in the rat was studied and found to closely correlate with tissue isozymic activity. A factor designated enhancer-site downstream binding protein (EDBP) was recently identified in the rat liver and found to interact with the proximal promoter of the class I ADH gene. The distribution of EDBP in nuclear extracts obtained from various tissues was examined based on its sequence-specific DNA binding property and found to correlate with tissue ADH expression. These findings suggest that EDBP is potentially a positive regulatory factor which is involved in controlling the tissue-specific expression of the ADH gene.
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Affiliation(s)
- M F Canto
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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31
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Montrose-Rafizadeh C, Blackmon DL, Hamosh A, Oliva MM, Hawkins AL, Curristin SM, Griffin CA, Yang VW, Guggino WB, Cutting GR. Regulation of cystic fibrosis transmembrane conductance regulator (CFTR) gene transcription and alternative RNA splicing in a model of developing intestinal epithelium. J Biol Chem 1992; 267:19299-305. [PMID: 1382071] [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] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Transcriptional and post-transcriptional regulation of CFTR (cystic fibrosis transmembrane conductance regulator) gene expression was studied in HT29 cells. It is known that the abundance of CFTR mRNA increases during differentiation of pluripotent HT29-18 cells and is maintained at high levels in the stably differentiated HT29-18-C1 subclone. Nuclear run-on assays suggest that increased transcription of the CFTR gene explains the increased abundance of total CFTR mRNA in differentiated HT29 cells. The increased transcription cannot be ascribed to cell cycle-dependent expression of the CFTR gene or to changes in CFTR gene copy number between subcloned cells. Similar to native tissue cells, differentiated HT29 cells contain low copy numbers of CFTR transcripts (1-5/cell), and a portion of the CFTR transcripts are alternatively spliced to remove exon 9 (and make 9-mRNA). During differentiation of HT29-18 cells, the absolute amount of full-length CFTR mRNA increases 8-fold, whereas the amount of 9- mRNA increases 18-fold. The fraction of 9- mRNA in the CFTR mRNA pool is increased in differentiated HT29 cells. The results show that gene transcription regulates the abundance of CFTR transcripts and that regulatory control of alternative RNA splicing may also be a cellular mechanism to modulate CFTR function.
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Affiliation(s)
- C Montrose-Rafizadeh
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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32
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Potter JJ, Mezey E, Cornelius P, Crabb DW, Yang VW. The first 22 base pairs of the proximal promoter of the rat class I alcohol dehydrogenase gene is bipartite and interacts with multiple DNA-binding proteins. Arch Biochem Biophys 1992; 295:360-8. [PMID: 1586166 DOI: 10.1016/0003-9861(92)90529-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [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: 12/27/2022]
Abstract
The rat class I alcohol dehydrogenase (ADH) gene is primarily expressed in the liver. We previously showed that the liver-enriched transcription factor, the CCAAT/enhancer binding protein (C/EBP), binds to the proximal promoter of the rat class I ADH gene between positions -11 and -22 relative to the start site of transcription. We now demonstrate that another transcription factor, the liver activator protein (LAP), also interacts with the same region of the promoter based on the following observations: (1) LAP synthesized by in vitro transcription and translation of cloned cDNA sequence forms complexes with an oligonucleotide containing the C/EBP-binding sequence within the ADH promoter as determined by the electrophoretic mobility shift assay (EMSA), (2) purified LAP interacts with the proximal ADH promoter when analyzed by the DNase I protection assay, and (3) an ADH promoter-reporter gene construct containing the C/EBP-binding site is transactivated by an eukaryotic expression vector containing the LAP sequence. EMSA of an oligonucleotide containing the first 22 base pairs (between positions -1 and -22) of the ADH promoter with rat liver nuclear extracts (RLNE) resulted in the formation of two major complexes. Complex 1 was competed away by a heterologous oligonucleotide containing a C/EBP-binding site within the promoter of the adipocyte 422 (aP2) gene, while complex 2 was not. Additional competition experiments with the ADH or 422 (aP2) oligonucleotide using either RLNE or extracts from 3T3-L1 adipocytes demonstrated that complex 1 contains either C/EBP or LAP, while complex 2 contains a DNA-binding protein that binds to a novel sequence 5'-TGGCCCAGTT-3' between positions -1 and -10 of the ADH promoter. Ultraviolet cross-linking between RLNE and a labeled oligonucleotide containing the above sequence indicates that this protein, designated EDBP (for enhancer-site downstream binding protein), has an estimated molecular weight of 47 kDa, which is larger than that reported for either C/EBP (42 kDa) or LAP (36 kDa).
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Affiliation(s)
- J J Potter
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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Potter JJ, Cheneval D, Dang CV, Resar LM, Mezey E, Yang VW. The upstream stimulatory factor binds to and activates the promoter of the rat class I alcohol dehydrogenase gene. J Biol Chem 1991; 266:15457-63. [PMID: 1869565] [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] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The gene encoding rat class I alcohol dehydrogenase (ADH) is expressed primarily in the liver. Recent studies in our laboratories indicate that multiple cellular factors present in the rat liver interact with various regions of the promoter of this gene. One of the regions contains the sequence 5'-CACATG-3' that has an "E box" homology to which a number of transcription factors containing the basic helix-loop-helix motif bind. We now demonstrate that the human transcription factor, upstream stimulatory factor (USF), a basic helix-loop-helix-containing protein, binds to and activates the promoter of the rat class I ADH gene. Electrophoretic mobility shift assays of labeled oligonucleotide containing the 5'-CACATG-3' sequence within the ADH promoter revealed the formation of multiple DNA-protein complexes when nuclear extracts obtained from adult rat liver were used. The binding of proteins to the DNA could be competed away with an oligonucleotide specifying a sequence within the adenovirus major late promoter (MLP) that had previously been shown to bind USF. Similar complexes were observed when electrophoretic mobility shift assays of labeled MLP oligonucleotide were performed with rat liver nuclear extracts. Conversely, nuclear extracts isolated from HeLa cells, cells known to have abundant USF, contain factors that interact with the sequence present in the ADH promoter. This interaction could be competed efficiently by the MLP oligonucleotide. USF synthesized in an in vitro transcription and translation system also binds to the ADH promoter as well as to the MLP. In addition, antiserum directed against USF recognizes factors present in the rat liver nuclear extracts that interact with the ADH promoter. Furthermore, transcription directed from both the ADH and the adenovirus major late promoters was inhibited by an oligonucleotide representing the USF-binding site within the ADH promoter in a cell-free in vitro transcription system. Lastly, an ADH promoter-reporter gene construct was transactivated by an eukaryotic expression vector containing USF in HepG2 cells co-transfected with the two constructs. These experiments demonstrate that USF is present in the rat liver and that it binds to and activates the promoter of the rat class I ADH gene in a sequence-specific manner.
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Affiliation(s)
- J J Potter
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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34
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Tse CM, Ma AI, Yang VW, Watson AJ, Levine S, Montrose MH, Potter J, Sardet C, Pouyssegur J, Donowitz M. Molecular cloning and expression of a cDNA encoding the rabbit ileal villus cell basolateral membrane Na+/H+ exchanger. EMBO J 1991; 10:1957-67. [PMID: 1712287 PMCID: PMC452875 DOI: 10.1002/j.1460-2075.1991.tb07725.x] [Citation(s) in RCA: 130] [Impact Index Per Article: 3.9] [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: 11/08/2022] Open
Abstract
A cDNA clone encoding a rabbit ileal villus cell Na+/H+ exchanger was isolated and its complete nucleotide sequence was determined. The cDNA is 4 kb long and contains 322 bp of 5'-untranslated region, 2451 bp of open reading frame and 1163 bp of 3'-untranslated area, with 70%, 91% and 40% identity to the human sequence, respectively. Amino acid sequence deduced from the longest open reading frame indicated a protein of 816 residues (predicted Mr 90,716) which exhibits 95% amino acid identity to the human Na+/H+ exchanger. The two putative glycosylation sites in the human Na+/H+ exchanger are conserved in this protein, suggesting that it is a glycoprotein. Stable transfection of the cDNA into an Na+/H+ exchanger deficient fibroblast cell line, established Na+/H+ exchange. The Na+/H+ exchanger was stimulated by serum and a phorbol ester but not by 8-Br-cAMP. In Northern blot analysis, the cDNA hybridized to a 4.8 kb message in rabbit ileal villus cells, kidney cortex, kidney medulla, adrenal gland, brain and descending colon and to a 5.2 kb message in cultured human colonic cancer cell lines, HT29-18 and Caco-2. In immunoblotting, a polyclonal antibody raised against a fusion protein of beta-galactosidase and the C-terminal 158 amino acids of the human Na+/H+ exchanger identified a rabbit ileal basolateral membrane protein of 94 kd and only weakly interacted with the ileal brush border membrane. In immunocytochemical studies using ileal villus and crypt epithelial cells, the same antibody identified basolateral and not brush border epitopes. Restriction analysis of genomic DNA with a 462 bp PstI-AccI fragment of the rabbit Na+/H+ exchanger strongly suggests the existence of closely related Na+/H+ exchanger genes. The near identity of the basolateral Na+/H+ exchanger and the human Na+/H+ exchanger plus the ubiquitous expression of this message suggests that the ileal basolateral Na+/H+ exchanger is the 'housekeeping' Na+/H+ exchanger.
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Affiliation(s)
- C M Tse
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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Potter JJ, Mezey E, Christy RJ, Crabb DW, Stein PM, Yang VW. CCAAT/enhancer binding protein binds and activates the promoter of the rat class I alcohol dehydrogenase gene. Arch Biochem Biophys 1991; 285:246-51. [PMID: 1654768 DOI: 10.1016/0003-9861(91)90356-n] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [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: 12/28/2022]
Abstract
CCAAT/enhancer binding protein (C/EBP), a DNA binding protein originally isolated from rat liver, activates the transcription of a number of liver-specific genes. We studied the effect of C/EBP on the transcription of the rat class I alcohol dehydrogenase gene. Purified C/EBP was shown to bind to a segment of the rat class I alcohol dehydrogenase gene promoter between position -10 and -22. Nuclear extracts isolated from rat liver contained a heat stable factor(s) that also bound to this sequence. Cotransfection experiments in HepG2 cells showed transactivation of alcohol dehydrogenase promoter-CAT fusion constructs by an expression vector containing wild-type C/EBP. Expression vector containing a mutated C/EBP that failed to bind DNA also failed to activate the promoter. These experiments demonstrate that C/EBP expression can activate the rat class I alcohol dehydrogenase gene promoter.
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Affiliation(s)
- J J Potter
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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Kern SE, Yardley JH, Lazenby AJ, Boitnott JK, Yang VW, Bayless TM, Sitzmann JV. Reversal by antrectomy of endocrine cell hyperplasia in the gastric body in pernicious anemia: a morphometric study. Mod Pathol 1990; 3:561-6. [PMID: 2235980] [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: 12/30/2022]
Abstract
Multifocal gastric carcinoid tumors occasionally develop in patients with pernicious anemia, associated with hyperplasia of endocrine cells in the atrophic and metaplastic gastric body mucosa. This constellation of findings probably requires a trophic drive from hypergastrinemia associated with antral G cell hyperplasia, a consequence of achlorhydria in these patients. We report a case in which antrectomy was performed on such a patient in order to abrogate the trophic stimulus. Antrectomy was followed by resolution of hypergastrinemia and a decrease in the size of polyps endoscopically. Nine months later, the gastric remnant was resected. Using morphometric techniques, endocrine cells in the initial antrectomy specimen (which included body mucosa at the resection line) were compared with those in the subsequently removed gastric body. Antrectomy resulted in striking decreases in number (137 versus 34/mm2; P = 0.0001) and size (93 versus 56 microns2; P = 0.0001) of endocrine cells of body mucosa. The findings suggest that antrectomy may be useful in the management of endocrine cell hyperplasia, and possibly also associated carcinoid tumors, in pernicious anemia.
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Affiliation(s)
- S E Kern
- Department of Pathology, Johns Hopkins Hospital, Baltimore, Maryland
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Abstract
Growth hormone has previously been shown to increase the activity of alcohol dehydrogenase in primary hepatocyte culture from male rats. In this study, continuous exposure of cultured hepatocytes to growth hormone (1 microgram/ml) resulted in parallel increased in the enzyme activity of alcohol dehydrogenase and immunoreactive protein. Growth hormone increased the incorporation of [3H]leucine into alcohol dehydrogenase protein relative to the incorporation into cytosolic protein. The abundance of alcohol dehydrogenase mRNA increased on Days 3 and 4 of continuous exposure of the hepatocytes to growth hormone and returned to control levels on Day 5 of culture. Growth hormone increased the rate of transcription of the alcohol dehydrogenase gene as demonstrated by nuclear runoff experiments. These observations indicate that the effect of growth hormone in enhancing alcohol dehydrogenase activity is due to increased synthesis of the enzyme which is initiated at the level of gene transcription.
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Affiliation(s)
- J J Potter
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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Christy RJ, Yang VW, Ntambi JM, Geiman DE, Landschulz WH, Friedman AD, Nakabeppu Y, Kelly TJ, Lane MD. Differentiation-induced gene expression in 3T3-L1 preadipocytes: CCAAT/enhancer binding protein interacts with and activates the promoters of two adipocyte-specific genes. Genes Dev 1989; 3:1323-35. [PMID: 2606350 DOI: 10.1101/gad.3.9.1323] [Citation(s) in RCA: 486] [Impact Index Per Article: 13.9] [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: 01/01/2023]
Abstract
Previous studies have shown that differentiation of 3T3-L1 preadipocytes leads to the transcriptional activation of a group of adipose-specific genes. As an approach to defining the mechanism responsible for activating the expression of these genes, we investigated the binding of nuclear factors to the promoters of two differentiation-induced genes, the 422(aP2) and stearoyl-CoA desaturase 1 (SCD1) genes. DNase I footprinting and gel retardation analysis identified two binding regions within the promoters of each gene that interact with nuclear factors present in differentiated 3T3-L1 adipocytes. One differentiation-induced nuclear factor interacts specifically with a single binding site in the promoter of each gene. Competition experiments showed that the interaction of this nuclear factor with the SCD1 promoter was prevented specifically by a synthetic oligonucleotide corresponding to the site footprinted in the 422(aP2) promoter. Several lines of evidence indicate that the differentiation-induced nuclear factor is CCAAT/enhancer binding protein (C/EBP), a DNA-binding protein first isolated from rat liver. Bacterially expressed recombinant C/EBP binds to the same site at which the differentiation-specific nuclear factor interacts within the promoter of each gene. Northern analysis with RNA from 3T3-L1 cells shows that C/EBP mRNA abundance increases markedly during differentiation. Transient cotransfection studies using a C/EBP expression vector demonstrate that C/EBP can function as a trans-activator of both the 422(aP2) and SCD1 gene promoters.
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Affiliation(s)
- R J Christy
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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Yang VW, Christy RJ, Cook JS, Kelly TJ, Lane MD. Mechanism of regulation of the 422(aP2) gene by cAMP during preadipocyte differentiation. Proc Natl Acad Sci U S A 1989; 86:3629-33. [PMID: 2542943 PMCID: PMC287191 DOI: 10.1073/pnas.86.10.3629] [Citation(s) in RCA: 66] [Impact Index Per Article: 1.9] [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: 01/01/2023] Open
Abstract
During differentiation of 3T3-L1 preadipocytes into adipocytes, expression of the gene encoding adipocyte 422(aP2) protein is activated. We have shown that the first 248 base pairs of the 422(aP2) gene promoter (which lacks a consensus cAMP response element) are sufficient to confer inducibility of a reporter gene by cAMP in preadipocytes. We now demonstrate by deletion analysis that this DNA segment contains overlapping negative and positive regulatory elements. The positive regulatory element contains a consensus activator protein 1 (AP-1) binding sequence. The effect of the negative regulatory element is observed in preadipocytes but not in fully differentiated adipocytes, suggesting that it is an important component of the regulatory mechanism governing expression of the 422(aP2) gene during differentiation. cAMP activates the 422(aP2) promoter in confluent preadipocytes but not in proliferating preadipocytes or fully differentiated adipocytes. The stimulatory effect of cAMP is abolished by deletions that enter the negative element, suggesting that cAMP increases expression by relieving the inhibitory effect of the negative regulatory element.
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Affiliation(s)
- V W Yang
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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Yang VW, Lerner MR, Steitz JA, Flint SJ. A small nuclear ribonucleoprotein is required for splicing of adenoviral early RNA sequences. Proc Natl Acad Sci U S A 1981; 78:1371-5. [PMID: 6940164 PMCID: PMC319132 DOI: 10.1073/pnas.78.3.1371] [Citation(s) in RCA: 191] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The size and structure of viral RNA species synthesized in nuclei isolated during the early phase of productive infection by adenovirus type 2 have been examined by electrophoresis in denaturing polyacrylamide cells and the nuclease S1 assay. The major products of transcription in vitro of early regions 1 and 2 in the adenoviral genome are processed RNA molecules that appear to be correctly spliced in isolated nuclei. Splicing of adenoviral RNA molecules is inhibited when nuclei are preincubated with antibodies from systemic lupus erythematosus patients that immunoprecipitate small nuclear ribonucleoprotein particles. The specificity of these antibodies suggests that ribonucleoprotein particles containing U1 RNA are required for splicing of the adenoviral RNA sequences we have examined.
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Yang VW, Binger MH, Flint SJ. Transcription of adenoviral genetic information in isolated nuclei. Characterization of viral RNA sequences synthesized in vitro. J Biol Chem 1980; 255:2097-108. [PMID: 6243656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The virus-specific RNA sequences synthesized in nuclei isolated from adenovirus type 2-infected HeLa cells comprise a fraction of the total RNA similar to that observed with RNA made in vivo. By 16 h after infection, for example, some 25% of the RNA made in isolated nuclei is transcribed from adenoviral DNA. Only 10 to 15% of the adenoviral RNA sequences synthesized in nuclei isolated during the late phase of infection are transcribed by form III RNA polymerase. This RNA, whose synthesis is resistant to 0.5 microgram/ml, but sensitive to 200 microgram/ml of alpha-amanitin, sediments at about 5 S in denaturing sucrose gradients and must, therefore, represent the virus-associated RNAs. The remainder of the sequences are transcribed by form II RNA polymerase and sediment as several RNA species in denaturing sucrose gradients. The largest of these exhibits the size, 55 to 60 S, expected of a complete transcript of the major, adenoviral transcriptional unit expressed during the late phase. Hybridization of RNA 32P-labeled in nuclei isolated during the late phase of infection to restriction endonuclease fragments of adenoviral DNA immobilized on nitrocellulose filters suggests that sequences of this transcriptional unit are indeed transcribed in vitro. To make a detailed assessment of the fidelity of transcription in isolated nuclei, transcription reactions were performed in the presence of 5-mercuricytidine 5'-triphosphate and the RNA mercurated in vitro separated from endogenous RNA by chromatography on sulfhydryl-agarose columns by a stringent procedure. After demercuration, RNA made in nuclei isolated 20 h following adenovirus type 2 infection was hybridized to the separated strands of restriction endonuclease fragments of 32P-labeled adenovirus type 2 DNA. Such RNA is complementary to the r strand of adenoviral DNA from 16.6 units to a point to the right of 98.3 units. These sequences comprise the major transcriptional unit expressed during the late phase (Fig. 1). It is therefore clear that the fidelity of transcription of adenoviral DNA by form II RNA polymerase is preserved in isolated nuclei. Two 1-strand transcriptional units, those of the IVa2 and ts36 genes (see Fig. 1) are also active at 20 h after infection. The results of similar analysis of RNA made in nuclei isolated 4 and 12 h after infection are also presented and discussed in terms of the mapping of individual transcriptional units within the type 2 adenoviral genome and the temporal regulation of adenoviral gene expression during productive infection.
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Abstract
Adenoviral RNA sequences synthesized in nuclei isolated during the late phase of productive infection comprise, besides virus-associated, VA, RNA, five major species, ranging in size from approximately 13S to 55S. The latter RNA species is of the length predicted if the major transcriptional unit expressed during the late phase were completely copied in vitro. Some 30% of the RNA sequences labeled in vitro are polyadenylated, and about one-third of the polyadenylated RNA is virus specific. Hybridization analysis of the sequences immediately adjacent to polyadenylic acid in late RNA labeled in isolated nuclei suggests that polyadenylation in vitro occurs at the same sites recognized within the cell. The polyadenylic acid-containing viral RNA sequences made in isolated nuclei are found in three major species of RNA, sedimenting at approximately 28S, 18S, and 13S. These sizes are remarkably similar to those reported for late mRNA species, suggesting that additional processing steps can occur in isolated nuclei. Hybridization of RNA to XhoI fragments of adenovirus type 2 DNA transferred to nitrocellulose filters reveals that sequences complementary to the region from 22.0 to 26.5 units present in 55S RNA are absent from all smaller species, suggesting that the smaller RNA species labeled in isolated nuclei are generated by splicing. The splicing events necessary to generate the 5' leader segment common to the majority of late adenoviral mRNA species are shown to be performed correctly in isolated nuclei.
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