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J Cell Biol March 22, 1999; 144 (6): 1083-96.

Roles of LAP2 proteins in nuclear assembly and DNA replication: truncated LAP2beta proteins alter lamina assembly, envelope formation, nuclear size, and DNA replication efficiency in Xenopus laevis extracts.

Gant TM , Harris CA , Wilson KL .

Humans express three major splicing isoforms of LAP2, a lamin- and chromatin-binding nuclear protein. LAP2beta and gamma are integral membrane proteins, whereas alpha is intranuclear. When truncated recombinant human LAP2beta proteins were added to cell-free Xenopus laevis nuclear assembly reactions at high concentrations, a domain common to all LAP2 isoforms (residues 1-187) inhibited membrane binding to chromatin, whereas the chromatin- and lamin-binding region (residues 1-408) inhibited chromatin expansion. At lower concentrations of the common domain, membranes attached to chromatin with a unique scalloped morphology, but these nuclei neither accumulated lamins nor replicated. At lower concentrations of the chromatin- and lamin-binding region, nuclear envelopes and lamins assembled, but nuclei failed to enlarge and replicated on average 2. 5-fold better than controls. This enhancement was not due to rereplication, as shown by density substitution experiments, suggesting the hypothesis that LAP2beta is a downstream effector of lamina assembly in promoting replication competence. Overall, our findings suggest that LAP2 proteins mediate membrane-chromatin attachment and lamina assembly, and may promote replication by influencing chromatin structure.

PubMed ID: 10087255
PMC ID: PMC2150574
Article link: J Cell Biol

Genes referenced: hsp90aa1.1 lmnb3 tbx2 tmpo
Antibodies: Lmnb3 Ab4

Article Images: [+] show captions
References [+] :
Alsheimer, Nuclear envelope remodelling during rat spermiogenesis: distribution and expression pattern of LAP2/thymopoietins. 1998, Pubmed

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