Genome-wide search identifies Ccnd2 as a direct transcriptional target of Elf5 in mouse mammary gland.
BACKGROUND
The 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.


RESULTS
Sequencing 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.


CONCLUSIONS
Identification 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.
Escamilla-Hernandez
Rosalba
R
Department of Biochemistry, State University of New York at Buffalo, Center for Excellence in Bioinformatics and Life Sciences, Buffalo, NY 14203, USA.
Chakrabarti
Rumela
R
Romano
Rose-Anne
RA
Smalley
Kirsten
K
Zhu
Qianqian
Q
Lai
William
W
Halfon
Marc S
MS
Buck
Michael J
MJ
Sinha
Satrajit
S
D000818:Animals; D047369:Chromatin Immunoprecipitation; D056742:Cyclin D2 / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D016678:Genome; D006801:Humans; D008321:Mammary Glands, Animal / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011247:Pregnancy; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*
C486196:Ccnd2 protein, mouse; D056742:Cyclin D2; D004268:DNA-Binding Proteins; C500759:Elf5 protein, mouse; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors