Evaluation of Putative Human Gamma Interferon Enhancers in a Murine B Cell Line

Abstract

In a stably transfected murine B cell clone containing the complete human INF-y (HuIFN-y) gene, treatment with phorbol 12-myristate 13-acetate (PMA) plus ionomycin produced a synergistic effect on the expression of the HuIFN-y gene. Cell lines containing an intronic deletion of 843 bp did not show this synergy. These data, plus DNase I hypersensitivity analysis indicated both 5'non-coding and first intronic regulatory sequences. To evaluate enhancer activity of these regions, specific sequences were linked to the reporter gene chloramphenicol acetyltransferase (CAT). Constructs were transiently transfected into a murine B cell line BCL-1, and assayed for enhancer activity. Experimental data indicate that a construct containing a portion of the 5'non-coding region and the first intronic region produced a minor synergistic response in CAT expression when treated with PMA plus ionomycin. Treatment of a plasmid containing 405 to 2716 bp sequence of the IFN-y gene, with murine IL-5 and dextran sulfate also resulted in a small increase in CAT expression. Overall the data suggest that regulation of the IFN-y gene may not only be due to developmental controls, but also to the presence of tissue specific factors.