CLONING AND CHARACTERIZATION OF THE PROMOTER FOR THE HUMAN-COMPLEMENTFACTOR-I (C36 C4B INACTIVATOR) GENE/

Complement factor I is a serine proteinase that regulates the classica l and alternative pathways of complement by cleaving C3b and C4b and p reventing the assembly of C3 and C5 convertase enzymes. In order to un derstand the regulation of factor I gene expression in liver cells, 4 kb of the 5' flanking region of the gene was cloned, and the 1474-bp 3 '-end was sequenced and shown to contain a number of transcription fac tor consensus sequences. A major and two minor transcription start sit es were identified, respectively, at 152, 178, and 198 bp upstream of the translation start site by primer extension analysis. The transcrip tional activity of the 1474-bp fragment was analyzed by fusion of 5' d eletion constructs to a cat-encoding gene expression vector and transi ent transfections into Hep G2 cells. A 273-bp fragment located at -112 to +161 relative to the major transcription start site was sufficient for promoter activity. The 3' fragment spanning +3 to +161 and contai ning a TATA-like element did not demonstrate promoter activity, sugges ting that the core promoter resides in a 115-bp sequence located betwe en -112 and +3. This region contains an Inr-like element overlapping t he major cap site and a CTF-NF1 element, two potential CCAAT boxes and an AP-2 element partially overlapping an Sp-1 site. Thus, factor I pr omoter may belong to the TATA-less Inr-driven class II promoters whose transcription is regulated by Sp-1. The transcriptional activity of t he 1474-bp 5' flanking fragment was upregulated by PMA, IL-6 and TNF-a lpha, suggesting that factor I may be an acute phase reactant. (C) 199 8 Elsevier Science B.V.