Abstract
BackgroundThe ETS transcription factor Elf5 (also known as ESE-2) is highly expressed in the mammary gland and plays an important role in its development and differentiation. Indeed studies in mice have illustrated an essential role for Elf5 in directing alveologenesis during pregnancy. Although the molecular mechanisms that underlie the developmental block in Elf5 null mammary glands are beginning to be unraveled, this investigation has been hampered by limited information about the identity of Elf5-target genes. To address this shortcoming, in this study we have performed ChIP-cloning experiments to identify the specific genomic segments that are occupied by Elf5 in pregnant mouse mammary glands.ResultsSequencing and genomic localization of cis-regulatory regions bound by Elf5 in vivo has identified several potential target genes covering broad functional categories. A subset of these target genes demonstrates higher expression levels in Elf5-null mammary glands suggesting a repressive functional role for this transcription factor. Here we focus on one putative target of Elf5, the Ccnd2 gene that appeared in our screen. We identify a novel Elf5-binding segment upstream of the Ccnd2 gene and demonstrate that Elf5 can transcriptionally repress Ccnd2 by directly binding to the proximal promoter region. Finally, using Elf5-null mammary epithelial cells and mammary glands, we show that loss of Elf5 in vivo leads to up regulation of Ccnd2 and an altered expression pattern in luminal cells.ConclusionsIdentification of Elf5-targets is an essential first step in elucidating the transcriptional landscape that is shaped by this important regulator. Our studies offer new toolbox in examining the biological role of Elf5 in mammary gland development and differentiation.
Highlights
The ETS transcription factor Elf5 is highly expressed in the mammary gland and plays an important role in its development and differentiation
We show that Elf5 binds to a conserved site within an upstream regulatory element as well as the proximal promoter of the Ccnd2 gene and that the expression level of cyclin D2 is upregulated by the loss of Elf5 in mammary epithelial cells in culture as well as in Elf5 deficient mammary glands
Our goal was to test if the N-20 antibodies are capable of recognizing its specific epitopes under harsh conditions, those typically associated with chromatin immunoprecipitation (ChIP) experiments such as formaldehyde crosslinking and stringent washing
Summary
The ETS transcription factor Elf ( known as ESE-2) is highly expressed in the mammary gland and plays an important role in its development and differentiation. The critical function of some of these Ets factors in mammary gland development, differentiation and tumorigenesis is dramatically reflected in the phenotypes observed in transgenic and knockout mouse studies [3] One such Ets factor is Elf ( called ESE2), which is highly restricted to tissues and organs rich in glandular or secretory epithelial cells including the mammary luminal epithelium [5,6]. Our studies have shown that Elf transcriptionally regulates the expression of key mediators of the Prolactin/ Jak2/Stat signaling pathway, and alterations in this pathway might be partly responsible for the Elf5-null mammary gland phenotype [10] These studies have unearthed a wealth of information about the biological role of Elf in mammary gland development and established Elf as a critical transcription factor that dictates cell fate and lineage choices
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