Regulation of nuclear envelope precursor functions during cell division.
Previously, we have shown that nuclear envelope assembly in cell-free extracts of Xenopus eggs requires two distinct vesicle-containing fractions, called Nuclear Envelope Precursor Fractions A and B (NEP-A and NEP-B). These fractions are characterized further in this paper and the manner in which they are regulated during metaphase is examined. Antisera against the NEP-B fraction recognized several proteins common to NEP-B and Xenopus oocyte or liver nuclei, but not to NEP-A or cytosol. A known glycoprotein component of the nuclear pore complex, p62, also co-fractionated with NEP-B, whereas the Xenopus egg lamin LIII did not. Together, these results provide further evidence that the NEP-B fraction contains precursors of the nuclear envelope. The regulation of NEP-A and -B function during metaphase, when the nuclear envelope is disassembled, was examined by treating each fraction with metaphase cytosol or purified protein kinase preparations isolated from metaphase-arrested eggs. Treatment of NEP-B with metaphase cytosol, under conditions where proteins are irreversibly phosphorylated, inhibited the subsequent assembly of the nuclear envelope by preventing the binding of NEP-B to chromatin. In contrast, similar treatment of NEP-A did not affect its ability to form nuclear envelopes. The changes in NEP-B during metaphase did not appear to be regulated directly by either p34cdc2/cyclin B, S6 kinase II or MAP kinase.
Vigers
G P
GP
Department of Cellular and Structural Biology, University of Colorado Health Sciences Center, Denver 80262.
Lohka
M J
MJ
D000818:Animals; D015153:Blotting, Western; D002455:Cell Division; D002843:Chromatin / Q000378:metabolism; D016213:Cyclins / Q000494:pharmacology; D008677:Metaphase; D009685:Nuclear Envelope / Q000502:physiology* / Q000648:ultrastructure; D009687:Nuclear Proteins / Q000378:metabolism / Q000502:physiology; D010766:Phosphorylation; D014981:Xenopus
D002843:Chromatin; D016213:Cyclins; D009687:Nuclear Proteins