Regulation of Id2 expression by CCAAT/enhancer binding protein beta.
Mice deficient for Id2, a negative regulator of basic helix-loop-helix (bHLH) transcription factors, exhibit a defect in lactation due to impaired lobuloalveolar development during pregnancy, similar to the mice lacking the CCAAT enhancer binding protein (C/EBP) beta. Here, we show that Id2 is a direct target of C/EBPbeta. Translocation of C/EBPbeta into the nucleus, which was achieved by using a system utilizing the fusion protein between C/EBPbeta and the ligand-binding domain of the human estrogen receptor (C/EBPbeta-ERT), demonstrated the rapid induction of endogenous Id2 expression. In reporter assays, transactivation of the Id2 promoter by C/EBPbeta was observed and, among three potential C/EBPbeta binding sites found in the 2.3 kb Id2 promoter region, the most proximal element was responsible for the transactivation. Electrophoretic mobility shift assay (EMSA) identified this element as a core sequence to which C/EBPbeta binds. Chromatin immunoprecipitation (ChIP) furthermore confirmed the presence of C/EBPbeta in the Id2 promoter region. Northern blotting showed that Id2 expression in C/EBPbeta-deficient mammary glands was reduced at 10 days post coitus (d.p.c.), compared with that in wild-type mammary glands. Thus, our data demonstrate that Id2 is a direct target of C/EBPbeta and provide insight into molecular mechanisms underlying mammary gland development during pregnancy.
Karaya
Kazuhiro
K
Department of Molecular Genetics, School of Medicine, University of Fukui 23-3 Shimoaizuki, Matsuoka, Fukui 910-1193, Japan.
Mori
Seiichi
S
Kimoto
Hisashi
H
Shima
Yoko
Y
Tsuji
Yoshihito
Y
Kurooka
Hisanori
H
Akira
Shizuo
S
Yokota
Yoshifumi
Y
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism*; D016384:Consensus Sequence; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D005260:Female; D051797:Inhibitor of Differentiation Protein 2; D008321:Mammary Glands, Animal / Q000378:metabolism*; D051379:Mice; D041681:NIH 3T3 Cells; D011247:Pregnancy; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000096:biosynthesis / Q000235:genetics*; D020218:Response Elements; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics*; D015533:Transcriptional Activation
D022782:CCAAT-Enhancer-Binding Protein-beta; D004268:DNA-Binding Proteins; C497452:Idb2 protein, mouse; D051797:Inhibitor of Differentiation Protein 2; D012097:Repressor Proteins; D014157:Transcription Factors