Inner nuclear membrane proteins and the nuclear lamina.

The nuclear lamina is a scaffolding structure at the nuclear periphery and is required for maintenance of nuclear shape, spacing of nuclear pore complexes, organization of heterochromatin, DNA replication, and regulation of transcription factors. The lamina is formed by type V intermediate filament proteins, Aand B-type lamins, which assemble to form a meshwork of 10-nm filaments underneath the inner nuclear membrane (INM). B-type lamins are constitutively expressed in all somatic cells and contain a stable C-terminal farnesyl modification, which mediates tight association with the INM. A-type lamins are expressed only in differentiated cells. They are components of the peripheral lamina and of structures in the nuclear interior. The lamina may be linked to nuclear pore baskets through Nup153.