The human gC1qR/p32 gene, C1qBP - Genomic organization and promoter analysis

gC1qR is an ubiquitously expressed cell protein that interacts with the glo bular heads of Clq (gC1q) and many other ligands. In this study, the 7.8-ki lobase pair (kb) human gC1qR/p32 (C1qBP) gene was cloned and found to consi st of 6 exons and 5 introns. Analysis of a 1.3-kb DNA fragment at the 5'-fl anking region of this gene revealed the presence of multiple TATA, CCAAT, a nd Sp1 binding sites. Luciferase reporter assays performed in different hum an cell lines demonstrated that the reporter gene was ubiquitously driven b y this 1.3-kb fragment. Subsequent 5' and 3' deletion of this fragment conf ined promoter elements to within 400 base pairs (bp) upstream of the transl ational start site. Because the removal of the 8-bp consensus TATATATA at - 399 to -406 and CCAAT at -410 to -414 did not significantly affect the tran scription efficiency of the promoter; GC-rich sequences between this TATA b ox and the translation start site may be very important for the promoter ac tivity of the C1qBP gene. One of seven GC-rich sequences in this region bin ds specifically to PANC-1 nuclear extracts, and the transcription factor Sp 1 was shown to bind to this GC-rich sequence by the supershift assay. Prime r extension analysis mapped three major transcription start regions. The fa rthest transcription start site is 49 bp upstream of the ATG translation in itiation codon and is in close proximity of the specific SP1 binding site.