DISASSEMBLY OF THE DROSOPHILA NUCLEAR LAMINA IN A HOMOLOGOUS CELL-FREE SYSTEM

Stage 14 Drosophila oocytes are arrested in first meiotic metaphase. A cell-free extract of these oocytes catalyzes apparent disassembly of purified Drosophila nuclei as well as of nuclear lamin polymers formed in vitro from isolated interphase lamins. Biochemically, the oocyte e xtract catalyzes lamin solubilization and phosphorylation as well as c haracteristic changes in one- and two-dimensional gel mobility. A prev iously unidentified soluble lamin isoform is easily seen after in vitr o disassembly. This isoform is detectable but present only in very sma ll quantities in vivo and is apparently derived specifically from one of the two interphase lamin isoforms. Cell-free nuclear lamina disasse mbly is ATP-dependent and addition of calcium to extracts blocks disas sembly as judged both morphologically and biochemically. This system w ill allow enzymological characterization of cell-free lamina disassemb ly as well as molecular analysis of specific Drosophila mutants.