AUGMENTATION OF GAMMA-GLOBIN GENE PROMOTER ACTIVITY BY CARBOXYLIC-ACIDS AND COMPONENTS OF THE HUMAN BETA-GLOBIN LOCUS-CONTROL REGION

Butyric acid increases fetal hemoglobin synthesis in adult animals and in erythroid cells in culture and induces the gamma-globin gene promo ter in transient expression experiments in K562 cells (McDonagh KT, Ni enhuis AW, Blood 78:255a, 1992 [abstr, suppl 1]). We compared the effe ct of butyrate and other short-chain carboxylic acids in transient exp ression studies with K562 cells using an expression plasmid bearing a luciferase reporter gene driven by the normal human (A) gamma-globin g ene promoter. Butyrate (4 carbons) increased the activity of the human (A) gamma-globin gene promoter up to 123 times. Marked augmentation o f the normal gamma-promoter activity was also noted with 5-carbon vale ric acid (up to 394 times) and 3-carbon propionic acid (up to 129 time s). The branched isobutyric acid as well as phenylacetate showed less ability to increase promoter activity. Addition of the tandemly repeat ed AP-1/NF-E2 (AP) enhancer sequences from hypersensitive site 2 (HS2) of the locus control region (LCR) increased gamma-promoter activity u p to 24 times. Addition of a nearby 16-bp conserved motif (CM) in HS2 (Safaya S, Rieder RF, Blood 78:146a, 1992 [abstr, suppl 1]) to the AP- containing plasmid construct further increased gamma-promoter activity . In the presence of butyrate, the plasmid bearing both the AP and CM sequences showed gene expression up to 477 times greater than that of the basal gamma-prometer-driven luciferase plasmid in the absence of i nducer. A plasmid bearing the herpes simplex thymidine kinase promoter was also tested and gene expression was markedly increased by the sam e organic acids. MEL cells responded to butyrate. valerate, and propio nate with induction of hemoglobin synthesis. Responses to isobutyrate and B-carbon caproate required higher concentrations of the compounds. Thus, other short-chain organic acids as well as butyrate increase ga mma-promoter activity in the transient expression system, and this act ivity can be further augmented by incorporating LCR elements into the expression vector. Nonglobin promoters also respond to the same carbox ylic acids. (C) 1994 by The American Society of Hematology.