Requirement of down‐regulation of NAD+ ADP‐ribosyltransferase for the interferon‐γ‐induced activation process of murine macrophage tumor cells

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Abstract
Expression of the NAD+ ADP-ribosyltransferase gene is depressed during interferon-gamma-induced activation of murine macrophage P388D1 tumor cells [Taniguchi, T., Yamauchi, K., Yamamoto, T., Tokushima, K., Harada, N., Tanaka, H., Takahashi, S., Yamamoto, H. & Fujimoto, S. (1988) Eur. J. Biochem. 171, 571-575]. In order to study the role(s) of NAD+ ADP-ribosyltransferase in interferon-gamma-induced activation of P388D1 cells, we transfected an cloned synthetase gene into P388D1 cells and examined the effect of exogenous transferase gene expression on the induction of the Ia antigen, one of the major histocompatibility gene products, by interferon-gamma. The transferase activity of the transfected cells was twice that of control cells, and Southern blot analysis revealed that characteristic restriction sizes of cDNA were detected in the clones. RNA blot analysis using a cDNA for the transferase as a probe showed that the level of mRNA for the transferase in transfected cells was higher than that in control cells, and mRNA for the exogenous transferase was still detectable 2 days after the transfected cells were treated with interferon-gamma. This indicates that the exogenous transferase gene was expressed in transfected cells. RNA blot analysis with a cDNA for the Ia antigen and flow-cytometric analysis showed that the Ia antigen was induced much less in the transfected cells by interferon-gamma, in terms of the mRNA and the Ia antigen. The results suggest that down-regulation of the transferase is required for the induction of the Ia antigen in P388D1 cells by interferon-gamma.