Summary Human DYRK1A gene encoding Dual-specificity tyrosine (Y)- Regulated Kinase 1A (DYRK1A) is a dosage-dependent gene whereby either trisomy or haploinsufficiency result in developmental abnormalities. However, the function and regulation of this important protein kinase are not fully understood. Here we report proteomic analysis of DYRK1A in human cells that revealed a novel role of DYRK1A in the DNA double-strand break (DSB) repair signaling. This novel function of DYRK1A is mediated in part by its interaction with ubiquitin-binding protein RNF169 that regulates the choice between homologous recombination (HR) and non-homologous end joining (NHEJ) DSB repair. Accumulation of RNF169 at the DSB sites promotes homologous recombination (HR) by limiting the recruitment of the scaffold protein 53BP1 that promotes NHEJ by protecting the DNA ends from resection. Inducible overexpression of active, but not the kinase inactive, DYRK1A in U-2 OS cells inhibited accumulation of 53BP1 at the DSB sites in RNF169-dependent manner. Mutation of DYRK1A phosphorylation sites in RNF169 or pharmacological inhibition of DYRK1A using harmine decreased the ability of RNF169 to displace 53BP1 from radiation-induced DSB sites. In order to further investigate the role of DYRK1A in regulation of DNA repair, we used CRISPR-Cas9 mediated knockout of DYRK1A in human and mouse cells. Interestingly, knockout of DYRK1A also caused a defect in 53BP1 DSB recruitment that was independent of RNF169, suggesting that dosage of DYRK1A can influence the DNA repair processes through several mechanisms. U-2 OS cells devoid of DYRK1A displayed an increased DNA repair and HR efficiency, and showed a decreased sensitivity to the PARP inhibitor olaparib when compared to control cells. Given evidence of its altered expression in human cancers, DYRK1A levels could represent a significant determinant of the DNA damaging therapy response.

DYRK1A regulates the recruitment of 53BP1 to the sites of DNA damage in part through interaction with RNF169