Incorporation of the nuclear pore basket protein Nup 153 into nuclear porestructures is dependent upon lamina assembly: evidence from cell-free extracts of Xenopus eggs

In cell-free extracts of Xenopus eggs that support the assembly of replicat ion-competent nuclei, we found that lamin B-3 specifically associates with four polypeptides (termed SLAPs, soluble lamin associated proteins), Here, one SLAP is identified as the nuclear pore complex protein Nup153, one memb er of the F/GXFG motif-containing nucleoporins. In vitro translated Nup153 and lamin B-3 co-immunoprecipitate, and lamin B-3 interacts specifically wi th the C-terminal domain of Nup153, During nuclear envelope assembly, other F/GXFG-containing nucleoporins are incorporated into the nuclear envelope preceding lamina assembly. Incorporation of Nup153 occurs at the same time as lamina assembly, When lamina assembly is prevented using the dominant-ne gative mutant XlaminB Delta 2+, Nup153 does not appear at the nuclear envel ope, while other F/GXFG-containing nucleoporins and Nup93 are recruited nor mally. When the lamina of pre-assembled nuclei is disrupted using the same dominant-negative mutant, the distribution of other nucleoporins is unaffec ted, However, Nup153 recruitment at the nuclear envelope is lost, Our resul ts indicate that both the recruitment and maintenance of Nup153 at the pore are dependent upon the integrity of the lamina.