DDB1 regulates GRK5 ubiquitination.

<p>(A) 293 T cells were co-transfected with GRK5-Flag, HA-Ub, DDB1, and Myc-CUL4A in various combinations as indicated. Cell lysate was immunoprecipitated with M2 affinity gel. The GRK5-ubiquitin complex was detected with anti-HA antibody after immunoblotting. (B) 293 T cells were co-transfected with GRK5-Flag, HA-Ub, control RNAi, DDB1RNAi, CUL4A RNAi, and CUL4B RNAi in various combinations as indicated. Cells were pretreated with 10 µM MG132 for 4 h, and GRK5-ubiquitin complex was examined as in A.