Fig. 6. MBK-2/DYRK2 phosphorylates MEX-5 at T₁₈₆ and primes for PLK-1 in C. elegans. (A) Kinase assay conducted using indicated substrates and kinases. MEX-5 used here is the fragment containing amino acids 117-270. The positions of MEX-5^117-270 (>), OMA-1 (#) and DYRK2 (<) are indicated. Assays with HsDYRK2 and MBK-2 were exposed differentially to get comparable signals for wild-type MEX-5^117-270. (B) Tandem kinase assays using MEX-5^FL WT or T₁₈₆A as substrate, first with HsDYRK2 (cold ATP), followed by HsPLK1 (³²P-ATP). The arrow marks the position of MEX-5^FL. Upper panel: ³²P incorporation visualized by autoradiography. Lower panel: Coomassie-stained gel. ^*, a contaminating band co-purified with MBK-2; A₁₈₆, T₁₈₆A; D₁₈₆, T₁₈₆D; DYRK2, HsDYRK2; KD, kinase dead; WT, wild type.