Depression in gene expression for poly(ADP‐ribose) synthetase during the interferon‐γ‐induced activation process of murine macrophage tumor cells

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Abstract
A 2.7-kb cDNA clone coding for bovine poly(ADP-ribose) synthetase was isolated from a .lambda.gt11 expression library by direct immunological screening with an antiserum to the enzyme. The cDNA hybridizes to an approximately 3.8-kb bovine thymus polyadenylated RNA, which translates an immunoprecipitable 120-kDa protein with the antibody to the enzyme. The partial DNA sequence of the cDNA was determined and portions of the predicted amino acid sequence matched the sequence of 26 amino acids at the N terminal of the 41-kDa .alpha.-chymotryptic fragment and two cyanogen-bromide-cleaved peptides of the enzyme. A subcloned fragment from the coding region of the cDNA was used as a probe to estimate the level of mRNA for the enzyme during the interferon-.gamma.-induced activation process of the murine macrophage tumor P388D1 cell line. The amount of mRNA for the enzyme decreased nearly completely within 24 h after incubation in a medium containing interferon-.gamma., while mRNA of the Ia antigen, one of the major histocompatibility gene products, was increased in the macrophage tumor cells by interferon-.gamma. as confirmed by the I-A.beta. cDNA as a probe. These results suggest that the gene expression for poly(ADP-ribose) synthetase is depressed during the interferon-.gamma.-induced activation process of macrophage tumor cells.