FIG. 5.

ERK2-mediated phosphorylation of GATA4 enhances its DNA binding activity. (A) EMSA demonstrates that ERK2 enhances the DNA binding activity of a bacterially purified GST-GATA4 (full-length) wild-type (Wt) fusion protein but not GST-S105A mutant GATA4 (full-length). (B) Western blot analysis with phospho-specific GATA4 (serine 105) antiserum using the same protein reactions used for panel A demonstrates efficient ERK2-mediated phosphorylation of full-length GATA4, but not the S105A mutant GATA4 or GST. (C) Western blot analysis with GATA4 antibody using the same extracts from panel A demonstrates equal protein levels.