Isolation of Daudi cells with reduced sensitivity to interferon. III. Interferon-induced proteins in relation to the phenotype of interferon resistance.

The pattern of both constitutive and interferon-induced proteins was determined by two-dimensional gel electrophoresis in parental and interferon-resistant clones of Daudi cells in relation to the phenotype of interferon resistance. The complement of constitutive proteins present in clones DIF3, DIF8, DIF9 and DIF10 appeared to be identical to that of parental Daudi cells even though these cells were resistant to both the antiviral and anti-proliferative actions of interferon. Treatment of Daudi cells for 20 h with 10(3) reference units/ml of electrophoretically pure human interferon-alpha resulted in the induction of 15 proteins of molecular weights ranging from 15000 to 62000 detected after a 4 h labelling period with L-[35S]methionine. A number of these proteins were also induced in interferon-resistant clones of Daudi cells although some of these proteins appeared later and in smaller amounts than in the interferon-treated parental cells. However, seven proteins with molecular weights ranging from 18000 to 58000 which were induced by interferon in parental Daudi cells were not induced in any of the four interferon-resistant clones, suggesting that the phenotype of interferon resistance of these cells may be related to a reduction or absence of certain interferon-induced protein(s).