Osteoprotegerin ligand induces beta-casein gene expression through the transcription factor CCAAT/enhancer-binding protein beta.
Osteoprotegerin ligand (OPGL, also known as RANKL), a member of the tumor necrosis factor superfamily, is essential for mammary gland development during pregnancy in addition to key roles in the immune system and bone development. Here we show that OPGL induces beta-casein transcription through the CCAAT/enhancer-binding protein beta (C/EBPbeta). In both HC11 cell lines and primary mammary epithelial cells, OPGL stimulation triggers rapid nuclear translocation of C/EBPbeta, which is critical for the expression of the beta-casein gene. Mutation of C/EBbeta binding sites in the beta-casein gene promoter completely abrogated OPGL-induced beta-casein promoter activity. By contrast, OPGL stimulation did not result in STAT5 phosphorylation. In vivo immunohistochemistry studies further demonstrated defective nuclear translocation of C/EBPbeta, but normal STAT5 activation, in OPGL-deficient mice. These data show that OPGL is a critical activator of beta-casein gene expression via the transcription factor C/EBPbeta. Our data provide new insights into the understanding of the molecular events involved in milk protein gene expression.
Kim
Hyun-Ju
HJ
Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, 790-784, Kyungbuk, South Korea.
Yoon
Mi-Jeong
MJ
Lee
Jinie
J
Penninger
Josef M
JM
Kong
Young-Yun
YY
D021581:Active Transport, Cell Nucleus; D000818:Animals; D001665:Binding Sites; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D002364:Caseins / Q000096:biosynthesis*; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002469:Cell Separation; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D015151:Immunoblotting; D007150:Immunohistochemistry; D008321:Mammary Glands, Animal / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008894:Milk Proteins; D008954:Models, Biological; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D053245:RANK Ligand; D012333:RNA, Messenger / Q000378:metabolism; D053246:Receptor Activator of Nuclear Factor-kappa B; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050799:STAT5 Transcription Factor; D015398:Signal Transduction; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism; D014158:Transcription, Genetic
D022782:CCAAT-Enhancer-Binding Protein-beta; D002352:Carrier Proteins; D002364:Caseins; D004268:DNA-Binding Proteins; D008562:Membrane Glycoproteins; D008894:Milk Proteins; D053245:RANK Ligand; D012333:RNA, Messenger; D053246:Receptor Activator of Nuclear Factor-kappa B; D050799:STAT5 Transcription Factor; C505687:Tnfrsf11a protein, mouse; C505689:Tnfsf11 protein, mouse; D015534:Trans-Activators