Abstract
Dual-specificity tyrosine-phosphorylated and regulated kinase (DYRK) proteins are an evolutionarily conserved family of protein kinases, with members identified from yeast to humans, that participate in a variety of cellular processes. DYRKs are serine/threonine protein kinases that are activated by autophosphorylation on a tyrosine residue in the activation loop. The family member DYRK1A has been shown to phosphorylate several cytosolic proteins and a number of splicing and transcription factors, including members of the nuclear factor of activated T cells family. In the present study, we show that DYRK1A autophosphorylates, via an intramolecular mechanism, on Ser-520, in the PEST domain of the protein. We also show that phosphorylation of this residue, which we show is subjected to dynamic changes in vivo, mediates the interaction of DYRK1A with 14-3-3beta. A second 14-3-3 binding site is present within the N-terminal of the protein. In the context of the DYRK1A molecule, neither site can act independently of the other. Bacterially produced DYRK1A and the mutant DYRK1A/S520A have similar kinase activities, suggesting that Ser-520 phosphorylation does not affect the intrinsic kinase activity on its own. Instead, we demonstrate that this phosphorylation allows the binding of 14-3-3beta, which in turn stimulates the catalytic activity of DYRK1A. These findings provide evidence for a novel mechanism for the regulation of DYRK1A kinase activity.