Functional interactions between aryl hydrocarbon and antioxidant/electrophile response elements : negative regulation of GST-Ya in vascular smooth muscle cells /
AhRE and ARE/EpRE are positive regulatory elements involved in coordinate regulation of mammalian gene expression by BaP and related xenobiotics. Activation of AhRE signaling is mediated by the AhR, while transacting factors involved in ARE/EpRE signaling is unknown. The rGST-Ya promoter was chose...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2000.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=731980701&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | AhRE and ARE/EpRE are positive regulatory elements involved in coordinate regulation of mammalian gene expression by BaP and related xenobiotics. Activation of AhRE signaling is mediated by the AhR, while transacting factors involved in ARE/EpRE signaling is unknown. The rGST-Ya promoter was chosen as a model to establish the functional interactions between AhRE and ARE/EpRE in vSMCs by BaP. Four rGST-Ya CAT constructs, 1.6CAT, -164CAT, AhRECAT and ARE/EpRECAT, were utilized in this work. Induction patterns of these four rGST-Ya CAT constructs by BaP show that AhRECAT is inducible by BaP but not 1.6CAT or ARE/EpRECAT in vSMCs. These results indicated that at least two negative mechanisms are operative within rGST-Ya promoter. We demonstrate that ARE/EpRE functions as a negative regulatory sequence within 1.6CAT and that a C/EBP site within the ARE/EpRE directs this negative mechanism. C/EBP-β and AhR interact with ARE/EpRE in supershift assays. We find that C/EBP-β or C/EBP-α represses 1.6CAT activity by BaP, while AhR has opposite effect. C/EBP-β or C/EBP-α also antagonizes the stimulatory effect of AhR on 1.6CAT activity. We also demonstrated that AhRE is the major enhancer sequence within rGST-Ya promoter responsive to BaP in vSMCs, and that ARE/EpRE represses chemical inducibility of the AhRE. The AhRE is also able to suppress ARE/EpRE activation. CBP protein level also limits 1.6CAT induction. This negative mechanism is supported by the findings that human adenovirus E1A protein abrogates the co-transactivation potential of CBP, while an E1A mutant (E1[][]2/36) does not. This dissertation reveals that multiple mechanisms mediate negative regulation of rGST-Ya in vSMCs by BaP. Among these negative mechanisms, we have shown that: 1) induction interference exists between AhRE and ARE/EpRE; 2) ARE/EpRE function as a negative regulatory sequence within rGST-Ya promoter; 3) a C/EBP site within ARE/EpRE mediates the negative ARE/EpRE mechanism; 4) C/EBP-β and AhR interact with the C/EBP site and function as negative regulators; 5) limiting intracellular CBP protein levels prevent induction of rGST-Ya; 6) C/EBP-β antagonizes AhR-directed activation of the AhRE by competition for the same binding proteins. A working model for rGST-Ya regulation is established for future studies on BaP target gene. |
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| Item Description: | Vita. "Major Subject: Toxicology". |
| Physical Description: | x, 185 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 135-184). |