A complex containing p34cdc2 and cyclin B phosphorylates the nuclear lamin and disassembles nuclei of clam oocytes in vitro.
Cell-free extracts prepared from activated clam oocytes contain factors which induce phosphorylation of the single 67-kD lamin (L67), disassemble clam oocyte nuclei, and cause chromosome condensation in vitro (Dessev, G., R. Palazzo, L. Rebhun, and R. Goldman. 1989. Dev. Biol. 131:469-504). To identify these factors, we have fractionated the oocyte extracts. The nuclear lamina disassembly (NLD) activity, together with a protein kinase activity specific for L67, appear as a single peak throughout a number of purification steps. This peak also contains p34cdc2, cyclin B, and histone H1-kinase activity, which are components of the M-phase promoting factor (MPF). The NLD/L67-kinase activity is depleted by exposure of this purified material to Sepharose conjugated to p13suc1, and is restored upon addition of a p34cdc2/p62 complex from HeLa cells. The latter complex phosphorylates L67 and induces NLD in the absence of other clam oocyte proteins. Our results suggest that a single protein kinase activity (p34cdc2-H1 kinase, identical with MPF) phosphorylates the lamin and is involved in the meiotic breakdown of the nuclear envelope in clam oocytes.
Dessev
G
G
Department of Cell, Molecular and Structural Biology, Northwestern University Medical School, Chicago, Illinois 60611.
Iovcheva-Dessev
C
C
Bischoff
J R
JR
Beach
D
D
Goldman
R
R
D000818:Animals; D049872:Bivalvia; D016203:CDC2 Protein Kinase / Q000302:isolation & purification / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D002875:Chromosomes / Q000502:physiology; D016213:Cyclins / Q000302:isolation & purification / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D034882:Lamins; D046911:Macromolecular Substances; D016200:Maturation-Promoting Factor / Q000502:physiology; D009685:Nuclear Envelope / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D009865:Oocytes; D010766:Phosphorylation; D013379:Substrate Specificity
D016213:Cyclins; D034882:Lamins; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D016203:CDC2 Protein Kinase; D016200:Maturation-Promoting Factor