LABORATORY AND ANIMAL STUDIES

Identification of CACATA cis-element and USF2 Transcription Factor Involved in the Expression of Cbfa1 Gene
GJ Wang, G Lee, W Hsu, CH Yeh, ML Ho, C Wang
Kaohsiung Medical University, Kaohsiung, Taiwan

Core binding factor 1 (Cbfa1) is one of the most important transcription factors that direct the osteogenesis of mesenchymal stem cells and osteoblastic functions. It is likely that the factors controlling Cbfa1 expression would trigger the early steps of osteoblast differentiation. By using reporter gene assay for 4.5 kb Cbfa1 promoter, it was found that the first 320 bp of Cbfa1 promoter are active in D1 cells. Within this region, electromobility shift assays (EMSAs) delineated a 6 bp of CACATG bound specifically by the proteins from D1 cell nuclear extract. Antibody super-shift and DNA-coupling magnetic bead pull-down assay indicated that the protein bound to this sequence is USF2. Site-specific mutagenesis revealed that this sequences contributed mainly to the activity of 320 bp Cbfa1 promoter. Thus, we concluded that USF2 is the major regulator for the expression of Cbfa1 gene.