p204 protein overcomes the inhibition of core binding factor alpha-1-mediated osteogenic differentiation by Id helix-loop-helix proteins.
Id proteins play important roles in osteogenic differentiation; however, the molecular mechanism remains unknown. In this study, we established that inhibitor of differentiation (Id) proteins, including Id1, Id2, and Id3, associate with core binding factor alpha-1 (Cbfa1) to cause diminished transcription of the alkaline phosphatase (ALP) and osteocalcin (OCL) gene, leading to less ALP activity and osteocalcin (OCL) production. Id acts by inhibiting the sequence-specific binding of Cbfa1 to DNA and by decreasing the expression of Cbfa1 in cells undergoing osteogenic differentiation. p204, an interferon-inducible protein that interacts with both Cbfa1 and Id2, overcame the Id2-mediated inhibition of Cbfa1-induced ALP activity and OCL production. We show that 1) p204 disturbed the binding of Id2 to Cbfa1 and enabled Cbfa1 to bind to the promoters of its target genes and 2) that p204 promoted the translocation from nucleus to the cytoplasm and accelerated the degradation of Id2 by ubiquitin-proteasome pathway during osteogenesis. Nucleus export signal (NES) of p204 is required for the p204-enhanced cytoplasmic translocation and degradation of Id2, because a p204 mutant lacking NES lost these activities. Together, Cbfa1, p204, and Id proteins form a regulatory circuit and act in concert to regulate osteoblast differentiation.
Luan
Yi
Y
Department of Orthopaedic Surgery, New York University School of Medicine, New York, NY 10003, USA.
Yu
Xiu-Ping
XP
Yang
Ning
N
Frenkel
Sally
S
Chen
Lin
L
Liu
Chuan-Ju
CJ
D000469:Alkaline Phosphatase / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D050657:Core Binding Factor alpha Subunits / Q000737:chemistry / Q000378:metabolism*; D005260:Female; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D051796:Inhibitor of Differentiation Proteins / Q000737:chemistry* / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D049790:Nuclear Export Signals; D009687:Nuclear Proteins / Q000378:metabolism*; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D015675:Osteocalcin / Q000235:genetics / Q000378:metabolism; D010012:Osteogenesis / Q000187:drug effects; D010750:Phosphoproteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D025801:Ubiquitin / Q000378:metabolism
C525718:BMP2 protein, human; C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D050657:Core Binding Factor alpha Subunits; C489664:Ifi16 protein, mouse; D051796:Inhibitor of Differentiation Proteins; D049790:Nuclear Export Signals; D009687:Nuclear Proteins; D010750:Phosphoproteins; D016212:Transforming Growth Factor beta; D025801:Ubiquitin; C406688:core binding factor alpha; D015675:Osteocalcin; D000469:Alkaline Phosphatase; D046988:Proteasome Endopeptidase Complex