Figure 2.

Organization of nuclear envelope in normal cells. The nuclear envelope consists of a double bilayer, the inner nuclear membrane (INM) and outer nuclear membrane (ONM). These membranes are connected at nuclear pores, a protein complex that permits diffusion and active transport of molecules across the envelope. The space between the ONM and INM, the perinuclear space (PNS), is traversed by the LINC (linker of nucleoskeleton and cytoskeleton) complex that is composed of KASH domain proteins (nesprins) anchored in the ONM and SUN proteins anchored in the INM. The lamina underlies the INM and is composed of intermediate filament proteins known as the lamins and is connected to the INM by proteins including the lamin B receptor (LBR) and LEM-domain proteins (Lap2-emerin-Man1). The lamina maintains nuclear shape and stability and serves as a scaffold for other nuclear proteins. BAF (Barrier-to-autointegration factor) binds LEM-domain proteins and chromatin. Phosphorylation of BAF during mitosis leads to its release from chromatin. Similarly, HP1 (heterochromatin protein 1) is a component of heterochromatin that links condensed chromatin to the INM through LBR.