10.6084/m9.figshare.1380304.v3 Faiza M Kalfalah Faiza M Kalfalah Elke Berg Elke Berg Morten O Christensen Morten O Christensen René M Linka René M Linka Wilhelm G Dirks Wilhelm G Dirks Fritz Boege Fritz Boege Christian Mielke Christian Mielke Spatio-temporal regulation of the human licensing factor Cdc6 in replication and mitosis Taylor & Francis Group 2015 Cdc 6 licensing factor Cdc 6 Biochemical fractionation abolishes G 2 phases replication S phase initiation loading factor Cdc 6 G 1 phase 2015-10-09 21:39:23 Dataset https://tandf.figshare.com/articles/dataset/Spatio_temporal_regulation_of_the_human_licensing_factor_Cdc6_in_replication_and_mitosis/1380304 <div><p>To maintain genome stability, the thousands of replication origins of mammalian genomes must only initiate replication once per cell cycle. This is achieved by a strict temporal separation of ongoing replication in S phase, and the formation of pre-replicative complexes in the preceding G1 phase, which "licenses" each origin competent for replication. The contribution of the loading factor Cdc6 to the timing of the licensing process remained however elusive due to seemingly contradictory findings concerning stabilization, degradation and nuclear export of Cdc6. Using fluorescently tagged Cdc6 (Cdc6-YFP) expressed in living cycling cells, we demonstrate here that Cdc6-YFP is stable and chromatin-associated during mitosis and G1 phase. It undergoes rapid proteasomal degradation during S phase initiation followed by active export to the cytosol during S and G2 phases. Biochemical fractionation abolishes this nuclear exclusion, causing aberrant chromatin association of Cdc6-YFP and, likely, endogenous Cdc6, too. In addition, we demonstrate association of Cdc6 with centrosomes in late G2 and during mitosis. These results show that multiple Cdc6-regulatory mechanisms coexist but are tightly controlled in a cell cycle-specific manner.</p></div>