FIG. 8.

The identity of the kinase docking domain determines the specificity of MAP kinases towards MEF2A. (A) Diagrammatic illustration of GST fusions to MEF2B, the MEF2B-MEF2A chimera, and MEF2A. The numbers of the N- and C-terminal MEF2A (italics) and MEF2B (roman type) amino acids are indicated above and below each construct. The p38-binding motifs in MEF2A and MEF2B are indicated by black and grey boxes, respectively, the amino acid sequences of these regions in MEF2A, MEF2B, MEF2C and MEF2D are shown, and identical residues are highlighted. (B) Kinase assays with the indicated GST fusion proteins and p38 MAP kinases were carried out as described in the legend to Fig. 1. (C) Diagram illustrating fusions of GST to MEF2A and MEF2AΔD and the chimeric proteins cJunδ-MEF2A, SAPD-MEF2A, and ElkD-MEF2A. These constructs contain the transcriptional activation domain of MEF2A and the kinase docking domain of cJun (δ), SAP-1 (D), Elk-1 (white box), MEF2A (black box), or no docking site, respectively. The numbers of the N- and C-terminal c-Jun/SAP-1/Elk-1 (italics) and MEF2A (roman type) amino acids are indicated above and below each construct, respectively. (D) Kinase assays with the indicated chimeric GST fusion proteins as substrates for MAP kinases (as indicated on the right) were carried out with 5 pmol of each protein for 15-min reactions as described in the legend to Fig. 1.