Characterization of a human apolipoprotein E gene enhancer element and its associated protein factors.

摘要: An enhancer element in the 5' flanking region of human apolipoprotein E gene, known as upstream regulatory 1 (URE1), has previously been implicated expression this gene. The URE1 element, which spans nucleotides -193 to -124 5'-flanking contains two sequences that bind nuclear proteins, determined by DNase I footprinting assay. In present study URE1, we have characterized these further. Deletion one footprint sequences, at -161 -141, reduced activity substantially. A 30-base pair oligonucleotide included protein-binding sequence was able, itself, act an enhancer. This sequence, termed positive for transcription (PET), demonstrated gel retention analysis least protein factors, is factor Sp1. Sp1 appeared be only required PET manifested. vitro assays showed necessary efficient directed apoE promoter and dominant promoter. Gel filtration chromatography oligonucleotide-affinity were used isolate a second PET-binding factor, Mr = 55,000 protein, from HeLa cell extracts. It compete with common binding site but it not activity. -184 -173, also bound Sp1, third Sp1-binding located proximal GC box (nucleotides -54 -45). had no activity, maximum transcriptional Thus, regulation gene influenced different playing major roles both basal