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. 2013 Jun 24;110(28):11445–11450. doi: 10.1073/pnas.1302676110

Fig. 3.

Fig. 3.

STAT3 associates with the MN–hexamer in a STAT3-Tyr705-phosporylation– and DNA-binding–independent manner, but enhances the MN–hexamer–directed transcription in a STAT3-Tyr705-phosporylation–dependent manner. (A–E) CoIP analyses in HEK293T cells, transfected with vectors as indicated at the top of each panel. The cells were treated with or without LIF 16 h before CoIP assays. Isl1 and Lhx3 associate with STAT3 in cells independently of LIF (A and B) and STAT3-Y705 phosphorylation (C). DNA-binding defective point mutants of Lhx3 and Isl1, Lhx3-N211S and Isl1-N230S, respectively, also associate with STAT3 (D and E). (F) Luciferase reporter assays in P19 cells using Hb9-MNe:LUC reporter with expression vectors as indicated below the graph. STAT3 WT, but not phosphorylation-defective STAT3F mutant, enhanced the activation of Hb9-MNe:LUC by coexpression of Isl1, Lhx3, and Ngn2 in the presence of LIF. Error bars represent the SD. *P < 0.05, **P < 0.005 in two-tailed Student t test.