The nuclear envelope in interphase animal cells is a remarkably stable structure consisting of a double membrane overlying a protein meshwork or lamina and penetrated by nuclear pore complexes. The envelope serves to regulate the exchange of macromolecules between the nucleus and cytoplasm and may serve to organize interphase chromatin sturcture. At the onset of mitosis the nuclear envelope rapidly disassembles. The membranes fragment to yield small vesicles and the lamina, which is composed of predominantly three polypeptides, lamins A, B and C (Mr 70, 67 and 62 kd), breaks down. Lamins A and C are dispersed as monomers throughout the mitotic cytoplasm, while lamin B remains associated with the nuclear membrane vesicles. In telophase, all of these components are reutilized to assemble nuclear envelopes around the newly segregated chromatids. This proposal presents a plan for the elucidation of mechanisms and molecules involved in the assembly process. We shall further define the roles of each of the nuclear lamins, and in addition we shall identify and characterize other soluble and membrane associated proteins involved in nuclear envelope reassembly. In particular we shall focus on molecules involved in recognition between and fusion of nuclear envelope derived vesicles. The strategy relies on the recent development of an in vitro nuclear envelope reassembly system. This system will be further refined such that envelopes can be assembles from purified components. In this way it will be possible to use such a fractionated assembly system to identify soluble components required for assembly and to examine more directly the roles of the individual lamins. Monoclonal and polyclonal antibodies will be prepared against nuclear envelope membrane proteins and these antibodies will be screened for their ability to block different aspects of the reassembly process in vitro. In particular, attention will be focussed on those membrane proteins which are specifically modified (by phosphorylation) during mitosis, since it is these which are most likely to play a role in the mitotic structural and functional rearrangements of the nuclear envelope.
| Pante, N; Bastos, R; McMorrow, I et al. (1994) Interactions and three-dimensional localization of a group of nuclear pore complex proteins. J Cell Biol 126:603-17 |
| McMorrow, I; Bastos, R; Horton, H et al. (1994) Sequence analysis of a cDNA encoding a human nuclear pore complex protein, hnup153. Biochim Biophys Acta 1217:219-23 |
| Narula, N; McMorrow, I; Plopper, G et al. (1992) Identification of a 200-kD, brefeldin-sensitive protein on Golgi membranes. J Cell Biol 117:27-38 |
| Conover, J C; Temeles, G L; Zimmermann, J W et al. (1991) Stage-specific expression of a family of proteins that are major products of zygotic gene activation in the mouse embryo. Dev Biol 144:392-404 |
