J Cell Sci 2007 Feb 01;120Pt 3:520-30. doi: 10.1242/jcs.03355.

Lamin B receptor plays a role in stimulating nuclear envelope production and targeting membrane vesicles to chromatin during nuclear envelope assembly through direct interaction with importin beta.

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Lamin B receptor (LBR), a chromatin and lamin binding protein in the inner nuclear membrane, has been proposed to play a vital role in nuclear envelope (NE) assembly. But the specific role for LBR in NE assembly remains unknown. In the present study, we show that overexpression of LBR causes membrane overproduction, inducing NE invagination and membrane stack formation, and that these processes require the transmembrane domain of LBR. Biochemical analysis shows that the N-terminal domain of LBR directly interacts with importin beta in a Ran sensitive and importin alpha independent manner. Using an in vitro NE assembly assay, we also demonstrate that blocking full length LBR binding sites on importin beta, by the addition of the LBR N-terminal domain inhibits the recruitment of LBR-containing vesicles to importin beta- or Ran-coated beads to form NE structure. Our results suggest that LBR is recruited to chromatin through direct interaction with importin beta to contribute to the fusion of membrane vesicles and formation of the NE.

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Species referenced: Xenopus
Genes referenced: kpnb1 lbr lmnb1 ran