MEMBERS OF THE FAMILY OF IL-6-TYPE CYTOKINES ACTIVATE STAT5A IN VARIOUS CELL-TYPES

Interleukin-6 (IL-6)-type cytokines activate transcription factors Sta t1 and Stat3 (signal transducers and activators of transcription). Her e we report that leukemia inhibitory factor (LIF) and IL-6 activate St at5a in M1 myeloid leukemia cells in addition. In murine embryonal ste m (ES) cells stably transfected with an expression vector for Stat5a t reatment with LIF resulted in tyrosine phosphorylation and DNA-binding of this transcription factor. Transfection of an expression construct for Stat5a in human hepatoma cells caused a dose-dependent increase i n LIF-triggered transcriptional activity. Our data demonstrate that St at5a is activated by IL-6-type cytokines and can mediate transcription al activity in addition to Stat1 and Stat3. (C) 1997 Academic Press.