When a eukaryotic cell divides the duplicated chromatin has to be segregated and enclosed by a new nuclear envelope, a double membrane that separates the nuclear interior from the cytosol. Failure in this key process results in alteration of gene expression patterns and genomic instability. Nuclear pore complexes (NPCs) are large protein structures that penetrate the nuclear envelope. They consist of 30 different proteins, nucleoporins, which form channels through which nucleocytoplamsic transport occurs. During cell division of higher eukaryotic cells nuclear pore complexes undergo a cycle of disassembly and reformation. In many tumor cells nuclear pore complexes reassemble not only into the NE but also into membranes of the cytosol, to form structures called annulate lamellae (AL). The mechanism of nuclear pore complex assembly and the function of annulate lamellae are unclear. The main focus of our research is to analyze the biogenesis of nuclear pore complexes and annulate lamellae. We intend to characterize the subcomplexes of the disassembled NPCs during mitosis and analyze their reassembly pathway into the reforming nuclear envelopes and cytoplasmic membranes (AL). This will provide new insights into the dynamics of nucleoporins and their role in the proliferation of normal and cancer cells.