Functional characterization of the bovine conglutinin promoter: Presence of a novel element for transcriptional regulation of a C-type mammalian lectin containing a collagen-like domain

Bovine conglutinin is a Ca2+-dependent serum lectin that is specific for N- acetylglucosamine and a member of the collectin (collagen-like lectin) fami ly. Here we report the identification of the cis-acting elements involved i n regulating expression of the conglutinin gene. The 5'-flanking region of the conglutinin gene was cloned and sequenced by gene walking using vector (cassette)-ligation mediated PCR, A genomic fragment encompassing -741 to 50 bp had significant promoter activity when linked to the luciferase repor ter gene and transfected into the human hepatoma cell line HepG2, Transfect ion analysis using a series of luciferase vector/5'-stepwise deletion mutan ts of the promoter constructs indicated that the sequence of 7 base pairs a t around - 180 bp from the transcription initiation site was necessary for the full expression of the conglutinin gene. The site-directed mutagenesis in the AP-1 (Activator Protein-1) sequence, immediately downstream of the p ositively controlling cis-element at around - 180 bp, resulted in a marked loss of the promoter activity. The novel positively controlling cis-element and the AP-1 sequence regulated synergistically the expression of the cong lutinin gene. Gel retardation assay and DNase I footprint analysis demonstr ated the presence of the nuclear proteins that bind to these two cis-elemen ts.