Reconstitution of lamin assembly on nuclear pore complex-containing membranes.

Intermediate filaments called lamins line the metazoan nuclear envelope and organize the nucleus and genome. Unlike actin and microtubules, purified intermediate filament proteins assemble into non-physiological structures, making it difficult to connect lamin functions to their assembly and regulation. To overcome this challenge, we reconstituted lamin assembly without nuclear assembly using interphase Xenopus laevis egg extracts that recapitulate physiological context. Mimicking nucleoplasm conditions triggers dispersed lamin assembly in egg extracts. Such ectopic lamin assembly occurs on nuclear pore complex-containing membranes, but does not recruit known nuclear lamina components, demonstrating that lamin assembly is separable from the rest of the nuclear lamina and nucleus. This assembly assay in the physiological context of cellular components opens the door to mechanistically dissecting nuclear lamina function in nuclear organization.