J Biol Chem, Vol. 274, Issue 7, 4017-4026, February 12, 1999
Hormone-dependent Recruitment of NF-Y to the
Uteroglobin Gene Enhancer Associated with Chromatin Remodeling in
Rabbit Endometrial Epithelium
Axel
Scholz,
Mathias
Truss, and
Miguel
Beato
From the Institut für Molekularbiologie und Tumorforschung,
Philipps Universität, Emil-Mannkopff-Strasse 2, D-35037 Marburg, Germany
Expression of the rabbit uteroglobin gene is
hormonally induced in cells of the endometrial epithelium during the
preimplantation phase of pregnancy. Here we show that progesterone
activation of the gene is mediated by two clusters of hormone
responsive elements located between 2.4 and 2.7 kilobase pairs upstream
of the transcriptional start site. Between these two clusters, genomic footprinting studies in the intact endometrial epithelium reveal the
hormone-inducible occupancy of several cis-acting elements. One of the protected elements shows sequence homology to the consensus binding site of the transcription factor NF-Y, which binds to the
element in gel shift experiments. This uteroglobin Y box is essential
for enhancer activity in transient transfection experiments with
endometrial and non-endometrial cell lines, in accordance with the
ubiquitous expression of NF-Y. To understand why binding of this
ubiquitous factor to the uteroglobin Y box in endometrium depends on
hormone induction, we examined the chromatin structure of the relevant
gene region. In the uninduced state, the enhancer region appears to be
organized into positioned nucleosomes. Upon hormone induction, this
nucleosomal pattern is lost and the enhancer region becomes
hypersensitive to nucleases, suggesting that a hormone-induced change
in the local chromatin structure unmasks previously unaccessible
binding sites for transcription factors. Our results emphasize the
limitations of using transient transfection assays for the functional
analysis of cis-acting elements and underline the need for
including the native chromatin organization in this kind of studies.
Copyright © 1999 by The American Society for Biochemistry and Molecular Biology, Inc.