THE HUMAN BONE SIALOPROTEIN GENE CONTAINS AN NF-E1 YY1 CIS-ACTING SEQUENCE WITH PUTATIVE REGULATORY ACTIVITY/

Bone sialoprotein (BSP) is a noncollagenous matrix glycoprotein locali zed predominantly in mineralized tissues but also detected in extraske letal sites undergoing focal mineralization. We have previously charac terized the human BSP gene and have shown that the upstream sequence c ontains inverted TATA and CCAAT motifs at the expected locations from the transcriptional start site (J. M. Kerr et al. [13]) and a potentia l YY1 binding motif located within the first 30 bp of intron 1 of the human gene. Deletion analyses of the human BSP promoter/exon 1 sequenc e fused to a CAT reporter gene indicate that CCAAT enhances basal tran scription of BSP in transiently transfected rat UMR106-01 BSP osteosar coma and rat skin fibroblasts. Though this enhancing activity was lost with inclusion of 68 bp of intron containing a YY1 motif in these con structs, reporter activity in the UMR106-01-BSP cells was elevated fou r- to seven-fold relative to that of rat fibroblasts. Gel electrophore tic mobility shift, UV-crosslinking, and southwestern experiments indi cate that YY1 is present only in the extracts of nuclei isolated from the UMR cells and may contribute to the elevated transcriptional activ ity of the human BSP promoter construct in UMR105-01-BSP.