The Notch-responsive transcription factor Hes-1 attenuates osteocalcin promoter activity in osteoblastic cells.
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.
Zhang
Ying
Y
Department of Cell Biology and Cancer Center, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.
Lian
Jane B
JB
Stein
Janet L
JL
van Wijnen
Andre J
AJ
Stein
Gary S
GS
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D024721:E-Box Elements / Q000235:genetics; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010006:Osteoblasts / Q000378:metabolism*; D015675:Osteocalcin / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D051381:Rats; D051880:Receptors, Notch / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism; D000072056:Transcription Factor HES-1; D014158:Transcription, Genetic
D051792:Basic Helix-Loop-Helix Proteins; D015415:Biomarkers; D018398:Homeodomain Proteins; D015675:Osteocalcin; D051880:Receptors, Notch; D012097:Repressor Proteins; D000072056:Transcription Factor HES-1; C489734:Hes1 protein, mouse