Cloning and characterization of the human selenoprotein P promoter - Response of selenoprotein P expression to cytokines in liver cells

We isolated an 18-kilobase (kb) genomic selenoprotein P clone from a human placenta library and cloned, sequenced, and characterized the 5'-flanking region of the human selenoprotein P gene. Sequence analysis revealed an intron between base pairs (bp) -13 and -14 upstream of the ATG codon and another one between bp 534 and 535 of the coding region. The major transcription start site of selenoprotein P in human HepG2 hepatocarcinoma cells was mapped to bp -70 by 5'-rapid amplification of cDNA ends and by primer extension, 1.8 kb of the 5'-flanking sequence were fused to a luciferase reporter gene, They exhibited functional promoter activity in HepG2 hepatocarcinoma and Caco2 colon carcinoma cells in transient transfection experiments, Treatment of transfected HepG2 cells with the cytokines interleukin 1 beta, tumor necrosis factor alpha, and interferon gamma repressed promoter activity, Nuclear extracts of interferon gamma-treated cells bound to a signal transducer and activator of transcription response element of the promoter in gel retardation experiments, By transfection of promoter-deletion constructs, a TATA box and a putative SP1 site were identified to be necessary for selenoprotein P transcription, These data indicate that the human selenoprotein P gene contains a strong promoter that is cytokine responsive, Furthermore, selenoprotein P, secreted by the liver, might react as a negative acute phase protein.