In cell-free extracts of Xenopus eggs that support the assembly of 
replication-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 member of 
the F/GXFG motif-containing nucleoporins. In vitro translated Nup153 and lamin 
B(3) co-immunoprecipitate, and lamin B(3) interacts specifically with 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-negative 
mutant XlaminB delta 2+, Nup153 does not appear at the nuclear envelope, while 
other F/GXFG-containing nucleoporins and Nup93 are recruited normally. When the 
lamina of pre-assembled nuclei is disrupted using the same dominant-negative 
mutant, the distribution of other nucleoporins is unaffected. However, Nup153 
recruitment at the nuclear envelope is lost. Our results indicate that both the 
recruitment and maintenance of Nup153 at the pore are dependent upon the 
integrity of the lamina.