During the cell cycle in the proliferative zone of the retina, similar to other parts of the central nervous system, the nucleus migrates back and forth through the neuroblastic layer (NBL), in an event called interkinetic nuclear migration. DNA is duplicated in the innermost margin, while mitosis occurs as the nucleus reaches the ventricular surface in each round of cell division. The G1 and G2 phases occur along the nuclear migration pathway. The relationship with the cell cycle and the control mechanisms of interkinetic nuclear migration are not well understood, but is known that this process occurs with the participation of the cytoskeleton and motor proteins. Casein kinase 2 (CK2) is a serine/treonine kinase indispensable in many cellular events, such as the control of the cell cycle and differentiation. This tetrameric enzyme has a large number of known substrates, including cell cycle regulators and motor proteins, like heavy and light chains of the molecular motor dynein. We tested whether INM is controlled by CK2. Double immunolabeling showed that CK2 is expressed in BrdU-labeled retinoblasts, and co-exists with dynein in the cytoplasm of this cells. INM was examined after pulselabeling of proliferating cells with BrdU in the retina of newborn rats, by following only the nuclear movement that occurs during G2-phase, from the basal to the apical side of the elongated retinoblasts. The CK2 specific inhibitor 4,5,6,7-tetrabromobenzotriazole (TBB) inhibited the activity of rat retinal CK2, and blocked nuclear movement in a dose-dependent way. No apoptosis was detected, and the total numbers of BrdU nuclei remained constant following treatment with TBB. Nonetheless, the CK2 inhibitor also blocked DNA synthesis, as shown by measuring the incorporation of [3H]-thymidine. TBB interrupts the mitosis process, as we found counting nucleus labeled with phospho-histone H3 and blocks the nuclear migration itself. Futhermore, a imunolabbeling of retina explantes for tubulin  showed that TBB treatment caused a microtubule disruption. Phospho-serine western blots of either control or TBB-treated retina indicate that TBB selectively inhibits the phosphorylation of certain proteins, consistent with inhibition of CK2. The results show that CK2 activity is required both for cell cycle and cytoskeleton dynamics regulation and for interkinetic nuclear migration in the developing retina. (CNPq, FAPERJ, PRONEX).