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Original Article |
Correspondence to: Robert D. Goldman, Department of Cell and Molecular Biology, Northwestern University Medical School, 303 E. Chicago Ave., Ward 11-145, Chicago, IL 60611. Tel:(312) 503-4215 Fax:(312) 503-0954 E-mail:r-goldman{at}nwu.edu.
The role of nuclear lamins in DNA replication is unclear. To address this, nuclei were assembled in Xenopus extracts containing AraC, a reversible inhibitor that blocks near the onset of the elongation phase of replication. Dominant-negative lamin mutants lacking their NH2-terminal domains were added to assembled nuclei to disrupt lamin organization. This prevented the resumption of DNA replication after the release of the AraC block. This inhibition of replication was not due to gross disruption of nuclear envelope structure and function. The organization of initiation factors was not altered by lamin disruption, and nuclei resumed replication when transferred to extracts treated with CIP, an inhibitor of the cyclin-dependent kinase (cdk) 2–dependent step of initiation. This suggests that alteration of lamin organization 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. Furthermore, the established organization of two elongation factors, proliferating cell nuclear antigen, and replication factor complex, was disrupted by 
NLA. These findings demonstrate that lamin organization must be maintained in nuclei for the elongation phase of DNA replication to proceed.
Key Words: DNA synthesis, lamina, intermediate filaments, nuclear organization, lamin mutant
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