Assayed by gel retardation, it is shown that IL-2 treatment on CTLL-2 causes formation of a DNA-binding factor that strongly recognizes a DNA sequence termed gammainterferon activation site (GAS). This DNA binding factor is named as IL-2 nuclear-activated factor (IL-2-NAF). The activation of IL-2-NAF is rapid and does not require protein synthesis. The level of IL-2-NAF activity increases within minutes of IL-2 stimulation and reaches maximum at 1 hour, then begins to decrease. Activation of IL-2-NAF is sensitive to an inhibitor for tyrosine protein kinasc (TPK)，but not to those specific for PKA or PKC. Moreover, protein tyrosine phosphatase(PTPase) or antibodies specific for phosphotyrosine(Anti-P-Tyr) can block the formation of IL-2-NAF-DNA complex. This demonstrates that activation of IL-2-NAF requires tyrosine phosphorylation. IL-4 or y-IFN treatment of CTLL-2 causes activation of common DNA-binding factors that recognize SIE(sis-inducible element)，but seems to have no effect on any DNA-binding factor that recognizes GAS. Thus, IL-2, IL-4 and γ-IFN induce their signals to nucleus by different path-ways in CTLL-2. The data also show that treatment of Hut-102 cell with IL-2 or IL-4 can weakly activate a DNA-binding factor specifically to recognize GAS.