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The notch‐responsive transcription factor Hes‐1 attenuates osteocalcin promoter activity in osteoblastic cells
Author(s) -
Zhang Ying,
Lian Jane B.,
Stein Janet L.,
van Wijnen Andre J.,
Stein Gary S.
Publication year - 2009
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.22299
Subject(s) - osteocalcin , transcription factor , microbiology and biotechnology , notch signaling pathway , promoter activity , runx2 , chemistry , promoter , biology , gene , alkaline phosphatase , gene expression , signal transduction , biochemistry , enzyme
Notch signaling plays a key role in osteoblast differentiation. A major transcriptional downstream regulator of this pathway is the helix–loop–helix (HLH) transcription factor Hairy/Enhancer of Split 1 (Hes‐1). Here we investigated the function of Hes‐1 in osteoblastic cells. Endogenous Hes‐1 gene expression decreases during progression of bone cell phenotype development in MC3T3‐E1 osteoblasts suggesting that it is a negative regulator of osteoblast differentiation. Forced expression of Hes‐1 inhibits osteocalcin (OC) mRNA levels, and luciferase assays indicate that Hes‐1 directly represses OC promoter activity. In vitro and in vivo protein/DNA interaction assays reveal that recombinant Hes‐1 binds specifically to an E‐box in the proximal promoter of the OC gene. Deletion of the Hes‐1 WRPW domain (MHes‐1) that recruits the co‐repressor Groucho abrogates repression of OC promoter activity by Hes‐1, but also blocks Hes‐1 binding to the promoter. The latter result suggests that exogenous Hes‐1 may be recruited to the OC promoter by both protein/DNA and protein/protein interactions. We conclude that the Notch‐responsive Hes‐1 protein is capable of repressing OC gene transcription in osteoblastic cells through an E‐box in the proximal promoter. Hes‐1 may contribute to osteoblast growth and differentiation by controlling basal bone‐specific transcription directly through interactions with transcriptional regulators that are known to bind to the OC gene promoter. J. Cell. Biochem. 108: 651–659, 2009. © 2009 Wiley‐Liss, Inc.