Fos and Jun inhibit estrogen-induced transcription of the human progesterone receptor gene through an activator protein-1 site.
The progesterone receptor (PR) gene is activated by estrogen in normal reproductive tissues and in MCF-7 human breast cancer cells. Although it is typically thought that estrogen responsiveness is mediated through estrogen response elements (EREs), the human PR gene lacks a palindromic ERE sequence. We have identified an activating protein-1 (AP-1) site at +745 in the human PR gene that bound purified Fos and Jun and formed a complex with Fos/Jun heterodimers present in MCF-7 nuclear extracts. Surprisingly, mutating the +745 AP-1 site in the context of a 1.5-kb region of the PR gene significantly enhanced estrogen receptor (ER) alpha-mediated transactivation, suggesting that the wild-type +745 AP-1 site plays a role in inhibiting PR gene expression in the presence of hormone. In support of this idea, transient transfection assays demonstrated that increasing levels of Fos and Jun repressed transcription of a reporter plasmid containing the +745 AP-1 site. Fos levels were transiently increased, ERalpha levels were decreased, and Jun was dephosphorylated after MCF-7 cells were treated with estrogen. Chromatin immunoprecipitation assays demonstrated that Jun was associated with the +745 AP-1 site in the endogenous PR gene in the presence and in the absence of estrogen, but that ERalpha and Fos were only associated with the +745 AP-1 site after estrogen treatment of MCF-7 cells. Our studies suggest that the human PR gene is regulated by multiple transcription factors and that the differential binding of these dynamically regulated trans-acting factors influences gene expression.
Petz
Larry N
LN
Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, 524 Burrill Hall, 407 South Goodwin Avenue, Urbana, Illinois 61801, USA.
Ziegler
Yvonne S
YS
Schultz
Jennifer R
JR
Nardulli
Ann M
AM
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism; D002478:Cells, Cultured; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D017124:Conserved Sequence; D004958:Estradiol / Q000494:pharmacology; D047628:Estrogen Receptor alpha; D004967:Estrogens / Q000494:pharmacology; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D009154:Mutation; D010766:Phosphorylation; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D011960:Receptors, Estrogen / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D011980:Receptors, Progesterone / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D020218:Response Elements; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014158:Transcription, Genetic
D002843:Chromatin; D047628:Estrogen Receptor alpha; D004967:Estrogens; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D018808:Transcription Factor AP-1; D004958:Estradiol