Regulation of cytochrome P-450IA1 gene expression /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1989.
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| Subjects: | |
| Online Access: | Link to ProQuest copy Link to OAKTrust copy ProQuest, Abstract |
| Abstract: | The mechanism by which cytochrome P-450IA1 gene expression is induced by polycyclic aromatic hydrocarbons and various polychlorinated dibenzo-p-dioxins involves an intracellular protein known as the Ah receptor. Within the past few years, a second protein has been identified which binds to certain polycyclic aromatic hydrocarbons (PAHs) but not to the receptor ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The protein, named the "4S PAH binding protein", has been reported to bind to a site on the DNA in the 5' regulatory region for the cytochrome P-450IA1 gene. This finding led to the hypothesis that the 4S PAH binding protein may be involved in the trans-regulation of this gene. The work presented in this manuscript addressed this hypothesis by (1) screening animals and cell lines for the presence or absence of the Ah receptor and 4S PAH binding protein, (2) screening polycyclic aromatic hydrocarbons (PAHs) to identify ligands which specifically bind only the 4S protein, (3) determining dose-response curves for TCDD and 4S protein specific ligands in mammalian cell lines, (4) co-administering a 4S binding protein ligand and TCDD in mammalian cell lines to determine the effects of the 4S protein-ligand complex on TCDD-induced cytochrome P-450IA1 expression, and (5) co-administering TCDD and 6-m ethyl-l,3,8- trichlorodibenzofuran (MCDF), a compound reported to be an antagonist of TCDD-induced benzo[a]pyrene-3-hydroxylase (AHH) activity, to determine whether antagonism occurs at the transcriptional level. The results of gradient assays show that the Ah receptor and the 4S binding protein were expressed in the rat strains which were studied. In the cell lines, H4IIE cells (rat hepatoma) expressed only the receptor whereas Hepalc1c7 cells (mouse hepatoma) expressed both proteins. In competition experiments, two compounds, benzo[e]pyrene and benzo[g,h,i]perylene, were shown to bind only to the 4S protein. When these ligands were co-administered with TCDD in the H4IIE and H epalclc7 cell lines, the induction of cytochrome P-450IA1 mRNA and AHH by TCDD was not altered. Also, MCDF did not alter the induction of cytochrome P-450IA1 mRNA by TCDD. These experiments indicate that ligands of the 4S protein and MCDF are not involved in the transregulation of cytochrome P-450IA1 gene expression. |
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| Item Description: | "Major subject: Biochemistry." Typescript (photocopy). Vita. |
| Physical Description: | xiii, 176 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |