In Vivo Footprinting of the Progestrone Receptor in Human Breast Cancer Cells
Abstract
Progesterone receptor gene expression is induced by estrogen in MCF-7 human breast cancer cells. Although it is generally thought that estrogen-responsiveness is mediated through estrogen response elements (EREs), the progesterone receptor gene lacks an identifiable ERE. The progesterone receptor A promoter does, however, contain a half ERE/Sp 1 binding site comprised of an ERE half site upstream of two Sp 1 binding sites. We have used in vivo DNase I footprinting to demonstrate that the half ERE/Sp 1 binding site is more protected when MCF-7 cells are treated with estrogen than when cells are not exposed to hormone suggesting that the this region is involved in estrogen-regulated gene expression. The ability of the half ERE/Sp 1 binding site to confer estrogen responsiveness to a simple heterologous promoter was confirmed in transient cotransfection assays. In vitro DNase I footprinting and gel mobility shift assays demonstrated that Sp 1 present in MCF-7 nuclear extracts and purified Sp 1 protein bound to the two Sp 1 sites and that estrogen-occupied estrogen receptor enhanced Sp 1 binding. In addition to its effects on Sp 1 binding, the estrogen receptor also bound directly to the ERE half site. Taken together, these findings suggest that estrogen-occupied receptor and Sp I play a role in activation of the human progesterone receptor A promoter.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1999
- Accession Number
- ADA379342
Entities
People
- Ann Nardulli
Organizations
- University of Illinois Urbana–Champaign