# ANTI-ESTROGEN RECEPTOR INTERACTION WITH DNA

> **NIH NIH R01** · UNIVERSITY OF ROCHESTER · 1994 · $179,329

## Abstract

The agent used most widely to treat women with breast cancer is the
triphenylethylene antiestrogen, trans-tamoxifen (TAM), which continues
to undergo extended trials as an adjuvant therapy in estrogen receptor
(ER) positive pre- and post-menopausal patients.  Although it is known
that TAM interferes with hormonal induction of specific genes, the exact
biochemical mechanisms by which this occurs are not understood.
Transcription is enhanced after estradiol (E2) and a dimeric ER protein
form a complex at a specific site on DNA, called an estrogen responsive
element (ERE), near the promoter of a responsive gene.  4-
Hydroxytamoxifen (4-OHT), an active metabolite of TAM, binds to the
ligand site of ER, but as results from our laboratory and others suggest,
the conformation of the ER is altered compared to that of E2-ER.  One of
our observations is that at saturation, the apparent molar amount of 4-
OHT-ER that can bind to either isolated cell nuclei, or plasmids bearing
EREs, is only about half that of E2-ER.  Among the explanations that we
will evaluate is that a conformational change induced upon 4-OHT-ER-ERE
complex formation, allows binding of only one, instead of the normal two,
ligands per ER dimer.  When several ERE sequences are in tandem, E2-ER
binds cooperatively, but 4-OHT-ER does not, indicating that the
conformational alteration in ER influences ER-ER interaction during DNA
binding.  Preliminary results show that antibodies to the DNA binding
domain of ER can differentially inhibit E2-ER vs. 4-OHT-ER binding,
revealing details of the conformational change.  Additional results
demonstrate that 4-OHT-ER dissociates more slowly from EREs than E2-ER.
Further information will be obtained by DNA footprint analysis.  The role
of ERE sequence, spacing and stereoalignment on ER-DNA binding parameters
will also be determined.  The effect of these changes in EREs on promoter
induction will be evaluated by transfection analyses.  Overall, results
will reveal structural and mechanistic consequences of 4-OHT binding to
the ER.

## Key facts

- **NIH application ID:** 2199182
- **Project number:** 5R01HD024459-05
- **Recipient organization:** UNIVERSITY OF ROCHESTER
- **SAM.gov UEI:** F27KDXZMF9Y8
- **Principal Investigator:** RUSSELL HILF
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1994
- **Award amount:** $179,329
- **Award type:** 5
- **Project period:** 1990-01-01 → 1996-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/2199182

## Citation

> US National Institutes of Health, RePORTER application 2199182, ANTI-ESTROGEN RECEPTOR INTERACTION WITH DNA (5R01HD024459-05). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/2199182. Licensed CC0.

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