The clam embryo protein cyclin A induces entry into M phase and the resumption of meiosis in Xenopus oocytes.
Fertilized clam embryos synthesize several new cell-cycle-related proteins. The cloned cDNA and derived amino acid sequences of one of these, cyclin A, are presented here. Immunoblots with an anti-cyclin A antibody reveal that cyclin A is undetectable in oocytes, appears within 15 min of fertilization, and is destroyed near the end of each meiosis and mitosis. We directly tested the ability of cyclin A to induce M phase by injecting SP6 cyclin A mRNA into Xenopus oocytes, which are arrested at the G2/M border of first meiosis. The injected mRNA was translated, with the result that the Xenopus oocytes entered meiosis. These findings indicate that the rise in cyclin A plays a direct and natural role in driving cells into M phase.
D000818:Animals; D049872:Bivalvia / Q000196:embryology*; D016213:Cyclins; D005260:Female; D007447:Invertebrate Hormones / Q000032:analysis / Q000235:genetics / Q000494:pharmacology*; D008540:Meiosis / Q000187:drug effects*; D008938:Mitosis / Q000187:drug effects*; D009865:Oocytes / Q000032:analysis / Q000166:cytology*; D011993:Recombinant Fusion Proteins; D014981:Xenopus; D015053:Zygote / Q000032:analysis / Q000166:cytology
D016213:Cyclins; D007447:Invertebrate Hormones; D011993:Recombinant Fusion Proteins