FIG. 6.

The synergistic enhancement of AR-dependent transactivation by Dyrk1A and Arip4 expression is independent of the kinase activity of Dyrk1A. (A) Dyrk1A with Arip4^WT or Arip4^Δ1165-1196 was expressed in CV-1 cells together with the MMTV-luciferase reporter gene. Cells were stimulated with the synthetic AR agonist R1881. Note that Arip4^Δ1165-1196, which lacks the Dyrk1A substrate consensus sequence, was also able to enhance the effect of Dyrk1A. WT, wild type. (B) Arip4 with Dyrk1A^WT or Dyrk1A^K188R was expressed in CV-1 cells together with the MMTV-luciferase reporter gene. Cells were stimulated with the synthetic AR agonist R1881. Note that kinase-deficient mutant Dyrk1A^K188R was able to stimulate AR-mediated activation not different from that stimulated by Dyrk1A^WT. Luciferase activities were normalized to protein content, and ratios were expressed relative to those obtained with AR in the presence of R1881 (value set at 1; second bar from left in panels A and B). Means and SEMs for three independent experiments are shown. For comparisons indicated by brackets, one asterisk indicates a P value of <0.05 and three asterisks indicate a P value of <0.0001.