E3 Ligase SCFβTrCP-induced DYRK1A Protein Degradation Is Essential for Cell Cycle Progression in HEK293 Cells

DYRK1A, located on the Down syndrome (DS) critical region of chromosome 21, was found to be overexpressed in brains of DS and Alzheimer's disease individuals. DYRK1A was considered to play important roles in the pathogenesis of DS and Alzheimer's disease; however, the degradation mechanism of DYRK1A was still unclear. In this study, we found that DYRK1A was degraded through the ubiquitin-proteasome pathway in HEK293 cells. The N terminus of DYRK1A that was highly unstable in HEK293 cells contributed to proteolysis of DYRK1A. E3 ligase SCF^βTrCP mediated ubiquitination and promoted degradation of DYRK1A through an unconserved binding motif (⁴⁹SDQQVSALS⁵⁷) lying in the N terminus. Any Ser-Ala substitution in this motif could decrease the binding between DYRK1A and β-transducin repeat containing protein (βTrCP), resulting in stabilization of DYRK1A. We also found DYRK1A protein was elevated in the G₀/G₁ phase and decreased in the S and G₂/M phase, which was negatively correlated to βTrCP levels in the HEK293 cell cycle. Knockdown of βTrCP caused arrest of the G₀/G₁ phase, which could be partly rescued by down-regulation of DYRK1A. Our study uncovered a new regulatory mechanism of DYRK1A degradation by SCF^βTrCP in HEK293 cell cycle progression.