Functions of the nuclear lamins

The nuclear lamina is a filamentous structure, composed of lamins, that sup ports the inner nuclear membrane. Several integral membrane proteins includ ing LBR (lamin B receptor), LAP (lamin-associated polypeptide) 1, and LAP 2 bind nuclear lamins in vitro and may influence lamin function and dynamics in vivo. Results from various studies suggest that lamins may have major f unctions in DNA replication, nuclear-envelope assembly, and nuclear-envelop e growth. Here we discuss experimental evidence that supports these hypothe ses and consider how interactions between lamins and other nuclear-envelope proteins, in particular LBR and LAP2 isoforms, may contribute to or altern atively mediate these functions of the lamina.