STUDY OF OSTEOBLAST-SPECIFIC EXPRESSION OF ONE MOUSE OSTEOCALCIN GENE- CHARACTERIZATION OF THE FACTOR-BINDING TO OSE2

In an attempt to understand the mechanisms of osteoblast-specific expr ession, we analyzed the promoter of the mouse osteocalcin gene 2, an o steoblast-specific gene. In this promoter, using a combination of DNA transfection experiments and DNA binding assays, we have identified tw o osteoblast-specific cis-acting elements called OSE1 and OSE2. Inspec tion of OSE2 DNA sequence and site-specific mutagenesis allowed us to define a core sequence for OSE2. This core sequence is identical to th e DNA binding site of the PEBP2 alpha transcription factors, the mouse homologues of the Drosophila Runt protein. Here we show that OSE2, th e factor present in osteoblast nuclear extracts and binding to OSE2, i s immunologically related to the PEBP2 alpha transcription factors. In DNA cotransfection experiment, a human homologue of PEBP2 alpha trans cription factor increases the activity of a short osteocalcin promoter through its binding to OSE2. Thus, this study presents evidence that OSE2 is a member of the PEBP2 alpha family of transcription factors.