Transcriptional regulatory elements for basal expression and effects of phenobarbital and dexamethasone onmRNA levels of rabbit CYP2C genes
Venepally, Pratap Rao
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/20392
Description
Title
Transcriptional regulatory elements for basal expression and effects of phenobarbital and dexamethasone onmRNA levels of rabbit CYP2C genes
Author(s)
Venepally, Pratap Rao
Issue Date
1992
Doctoral Committee Chair(s)
Kemper, Byron W.
Department of Study
Biology
Discipline
Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Molecular
Biology, Cell
Biology, Animal Physiology
Language
eng
Abstract
Cytochrome P450 (CYP) genes, expressed in many species, are involved in the oxidative metabolism of many xenobiotis as well as endogenous compounds. Expression of the rabbit CYP2C1 gene is observed only after induction with phenobarbital and is confined to the liver. The CYP2C2 gene is inducible in both liver and kidney. In order to identify the DNA domains involved in the regulation of general as well as hepatic-specific transcription, 5$\sp\prime$-flanking fragments from CYP2C1 (C1) and CYP2C2 (C2) genes were inserted in front of the firefly luciferase reporter gene and analyzed for promoter activity in HepG2 (hepatic) and COS-1 (non-hepatic) cells. Maximum basal expression in HepG2 and COS-1 cells was observed when the constructions contained C1 and C2 gene fragments that extended to $-$2000 and $-$410 bp (base pairs), respectively.
In other studies, effects of dexamethasone and phenobarbital, either separately or in conjunction with each other, on the rabbit CYP2C mRNA levels have been analyzed by dot blot hybridizations. Phenobarbital increased CYP2C1, CYP2C2, and CYP2C4 mRNAs markedly, but had only a slight positive effect on CYP2C3 mRNA levels. Dexamethasone treatment resulted in a 2.5 to 4-fold induction in the mRNA levels of all four. Dexamethasone also induced CYP2C3 mRNA to a greater extent than phenobarbital. The levels of CYPC2 and CYPC3 mRNA obtained from the rabbits treated with both phenobarbital and dexamethasone were not significantly different from those observed in the rabbits treated with either phenobarbital or dexamethasone alone. However, compared to the phenobarbital induction, the simultaneous exposure to both phenobarbital and dexamethasone resulted in an increase in CYP2C4 mRNA and a decrease in CYP2C1 mRNA levels.
In HepG2 cells phenobarbital and phenobarbital-like compounds such as 2-allyl-2-isopropylacetamide (AIA) and 2-propyl-2-isopropylacetamide (PIA) inhibited activity from CYP2C1 promoter by about 60% compared to that observed in untreated control. Treatment with compounds that either activate protein kinase C or elevate intracellular cyclic AMP levels had no effect on the induction of CYP2C1 promoter activity by phenobarbital. (Abstract shortened with permission of author.)
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
