Disruption of nuclear lamin organization blocks the elongation phase of DNA replication

The role of nuclear lamins in DNA replication is unclear. To address this, nuclei were assembled in Xenopus extracts containing AraC, a reversible inh ibitor that blocks near the onset of the elongation phase of replication, D ominant-negative lamin mutants lacking their NH2-terminal domains were adde d to assembled nuclei to disrupt lamin organization. This prevented the res umption of DNA replication after the release of the AraC block. This inhibi tion of replication was not due to gross disruption of nuclear envelope str ucture: and function,The organization of initiation factors was not altered by lamin disruption, and nuclei resumed replication when transferred to ex tracts treated with CIP, an inhibitor of the cyclin-dependent kinase (cdk) 2-dependent step of initiation. This suggests that alteration of lamin orga nization does not affect the initiation phase of DNA replication. Instead, we find that disruption of lamin organization inhibited chain elongation in a dose-dependent fashion. Further-more, the established organization of tw o elongation factors, proliferating cell nuclear antigen, and replication f actor complex, was disrupted by Delta NLA. These findings demonstrate that lamin organization must be maintained in nuclei for the elongation phase of DNA replication to proceed.