Fig. 1.

The nuclear envelope. The NE is an integral part of the ER-membrane network (in blue-green). The inner nuclear membrane (INM) and outer nuclear membrane (ONM) connect at sites of NPCs (green barrels) where the membrane curves as it surrounds the NPC. The ONM is continuous with the peripheral ER. The NE contains a variety of proteins that are embedded in the INM (purple) or the ONM (light blue). Most ONM proteins are also found in the peripheral ER. INM proteins can interact with the underlying nuclear lamina (dark blue), with ONM proteins or with chromatin (red), often through linker proteins (yellow). For a detailed description of the various proteins associated with the NE see recent reviews (Crisp and Burke, 2008; Guttinger et al., 2009).