Fig. 3. Kinase activity of VRK1 is required for the nuclear accumulation of CCND1. (A) Immunofluorescence of CCND1 (green) and VRK1 (red) from cells expressing wild-type (WT) or the kinase-dead (KD) mutant of VRK1. (B) Cytoplasmic (Cyt.) and nuclear (Nuc.) lysates of HeLa cells transfected with mock vector (pFlag-CMV2), kinase-dead (VRK1-KD) or wild-type (VRK1-WT) VRK1 were immunoblotted with the indicated antibodies. Protein disulfide isomerase (PDI) and Lamin B were used as markers for the cytoplasm and nucleus, respectively. Scale bars: 20 µm.