Cloning and characterization of the rat bone sialoprotein gene promoter

To study the transcriptional regulation of the rat bone sialoprotein (BSP) gene, the nucleotide sequence of a approximately 1 kb HindIII/KpnI subfragment from a genomic clone containing the 5' flanking sequence, exon 1 and part of intron 1 was determined and the transcription start site defined. This region includes an inverted TATA element (nt -24 to -19), an inverted CCAAT box, a homeobox-binding site, a putative 1,25-dihydroxyvitamin D3 response element (VDRE) sequence overlapping the inverted TATA sequence, and a novel 18 nt palindrome that may control the tissue-specific transcription of the BSP gene. The shortest promoter sequence capable of directing bacterial chloramphenicol acetyltransferase reporter gene expression included the inverted TATA element and the inverted CCAAT box. However, the promoter activity was down-regulated by 1,25-dihydroxyvitamin D3, indicating that the unique VDRE-like sequence overlapping the TATA element is functional. Thus the rat BSP gene promoter is characterized by novel cis-acting elements that may be involved in hormone- and tissue-specific regulation of transcription.