The molecular regulation of nuclear dynamics during cell cycle.

板层相关多肽(LAP)2是一种与B-型层蛋白和染色体直接相互作用的整膜蛋白，特异性分布于核膜内层。LAP2的染色质和层蛋白结合活性表明，LAP2在将有丝分裂小泡定位到染色体上以及在有丝分裂结束时重组核结构方面发挥着重要作用。本研究以LAP2的核质结构域为诱饵，进行了酵母双杂交筛选，以确定LAP2蛋白在核结构重构过程中与之相互作用的蛋白质。在这里，我鉴定了一种LAP2相互作用蛋白，称为L2BP1(LAP2结合蛋白1)。据预测，大鼠L2BP1基因编码89个氨基酸的蛋白质，它是小鼠和人的BAF(Barrier-to-AutoIntegration Factor)的大鼠同源物。BaF/L2BP1在间期细胞中弥漫分布于细胞核内。然而，在M期，它高度集中在染色体上。此外，LAP2的BAF/L2BP1结合区与其染色体结合区重叠。这些发现表明，BAF/L2BP1是LAP2-染色体相互作用的候选介体，可能参与了核结构改革第一步中染色体上膜运输的靶点。

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.