The molecular regulation of nuclear dynamics during cell cycle.

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Lamina-associated polypeptide (LAP) 2, which directly interacts with B-type lamins and chromosomes, is an integral membrane protein specifically distributed along the inner nuclear membrane of the nuclear envelope. The chromatin- and lamin- binding activity of LAP2 suggests that LAP2 plays an important role in targeting mitotic vesicles to chromosomes and reorganizing the nuclear structure at the end of mitosis.In the present study, in order to identify a protein with which the LAP2 protein interacts during nuclear architecture reformation, a yeast two-hybrid screen using the nucleoplasmic domain of LAP2 as a bait, was carried out. Here I identified a LAP2 interacting protein, termed L2BP1 (LAP2 binding protein 1). The rat L2BP1 cDNA sequence is predicted to encode a protein of 89 amino acids which turns out to be a rat homolog of mouse and human BAF (Barrier-to-Autointegration Factor). BAF/L2BP1 is distributed diffusely throughout the nucleus in interphase cells. It is, however, highly concentrated at the chromosomes during the M-phase. Further, the BAF/L2BP1 binding domain of LAP2 overlaps its chromosome-binding region. These findings suggest that BAF/L2BP1 is a candidate mediator of LAP2-chromosome interaction at the end of mitosis, and may participate as targeting sites on chromosomes for membrane traffic in the first step of nuclear architecture reformation.