Detailed Analysis of Transcriptional Regulation by Activation Functions-1 and -2 of the Human Estrogen Receptor
McInerney, Eileen M.
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https://hdl.handle.net/2142/87257
Description
Title
Detailed Analysis of Transcriptional Regulation by Activation Functions-1 and -2 of the Human Estrogen Receptor
Author(s)
McInerney, Eileen M.
Issue Date
1997
Doctoral Committee Chair(s)
Katzenellenbogen, Benita S.
Department of Study
Molecular and Integrative Physiology
Discipline
Molecular and Integrative Physiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Molecular
Language
eng
Abstract
The human estrogen receptor (ER), is a 66 kilodalton, ligand-inducible transcription factor that regulates the transcription of estrogen-responsive genes. Like other steroid hormone receptors, the ER is a modular protein that can be divided into separable domains with specific functions, such as ligand binding, dimerization, DNA binding, and transactivation. The ER contains two distinct activation domains that are involved in transcription activation. Activation function-1 (AF-1) is located in the amino-terminal A/B domain and activation function-2 (AF-2) is near the carboxyl-terminus in the E domain. In most cell and promoter contexts, AF-1 and AF-2 act synergistically to allow full transcriptional activity of ER. Our studies were designed to examine the transcriptional activity of ER and focus on both the amino- and carboxyl-terminal activation domains. We have demonstrated a functional interaction between the amino- and carboxyl-terminal regions of ER, that was promoted by both estradiol and antiestrogen binding. This interaction was transcriptionally productive, however, only in the presence of estradiol. In subsequent studies, we examined the ability of the steroid receptor coactivator-1 (SRC-1) protein to facilitate the integration of the amino- and carboxyl-terminal functions of ER. We have found that SRC-1, which has been shown to significantly increase ER transcriptional activity, enhanced the interaction, mediated by either estrogen or antiestrogen, between the amino- and carboxyl-terminal regions of ER. This enhanced interaction resulted in increased transcriptional activity only in the presence of estradiol. We also analyzed the A/B domain of ER and its role in the transcriptional activity of ER elicited by estrogens and antiestrogens. Studies showed that AF-1 contained a discrete region necessary for antiestrogen agonism that was not required for estradiol-stimulated activity. Also, we characterized V364E, a novel ER mutant containing a single amino acid substitution at residue 364 in the hormone binding domain, that is a transcriptionally active receptor variant, yet was able to significantly suppress wild type ER activity when both receptors were present together in cells. Together, these studies contribute toward elucidating the detailed biochemical mechanism of activated transcription by the ER.
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