DYNAMIC REMODELING OF NUCLEAR ARCHITECTURE DURING THE CELL-CYCLE

The nuclear matrix is an integral part of nuclear structure which unde rgoes a profound reorganization during the cell cycle reflecting major changes in functional requirements. This includes the processes of DN A replication and gene expression at interphase and partitioning of th e nuclear contents during mitosis. Using a monoclonal antibody (mAb2A) which specifically stains a novel nuclear meshwork which reorganizes during the cell cycle in Drosophila, we have initiated a study to: 1) more closely analyze this structural reorganization; 2) clone and char acterize the antigens recognized by this antibody; and 3) isolate othe r interacting proteins in order to gain insight into the regulation of this process. The mAb2A-labeled structure changes from what appears a s a diffuse meshwork at interphase to a distinct spindle-like scaffold at prophase. Since at metaphase the microtubules of the mitotic appar atus co-localize with the mAb2A spindle structure, a model is consider ed whereby the nuclear mAb2A-labeled scaffolding reorganizes during th e cell cycle to provide a guide for the establishment of the mitotic a pparatus. The mAb2A has identified two separate antigens, each of whic h shows similar distribution patterns. One of these antigens has been partially cloned and contains an unusual tandem ser-thr kinase domain. The association of this kinase homologue with a nuclear scaffold whic h reorganizes during the cell cycle suggests that it may be involved i n regulating changes in nuclear architecture during the cell cycle and /or in mediating the downstream consequences of such changes. (C) 1996 Wiley-Liss, Inc.