Signal transducer and activator of transcription 3 (STAT3), which mediates biological actions in many physiological processes, is activated by cytokines and growth factors via specific tyrosine or serine phosphorylation, dimerization and nuclear translocation. A recent study has demonstrated, by using antibody to acetylated lysine, and a STAT3 mutant with Lys-685-to-Arg substitution, that STAT3 is acetylated at Lys-685 by histone acetyltransferase p300, and that acetylation at Lys-685 is critical for STAT3 activation. In the present study, we created an acetyl-specific antibody against STAT3 acetylated at Lys-685, and found that leukemia inhibitory factor (LIF) or interleukin (IL)-6 induced acetylation of STAT3 at Lys-685 in 293T and Hep3B cells. Moreover, acetylation of STAT3 at Lys-685 was suppressed by PI3K inhibitor LY294002, or a dominant negative Akt. Taken together, our findings demonstrate that endogenous STAT3 is acetylated at Lys-685 by LIF or IL-6 through PI3K/Akt activation.
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