Figure 1.

Structure and activity of cyclin B1-derived fusion proteins. A NLS or nonfunctional mutant NLS (NLS^mut) was fused to the N terminus of derivatives of Xenopus cyclin B1. B1 refers to wild-type cyclin B1. B1^Ala has Ser → Ala substitutions at residues 94, 96, 101, and 113, and B1^Glu has Ser → Glu substitutions at residues 94, 96, 101, and 113. CRS^Ala and CRS^Glu contain Ser → Ala or Ser → Glu substitutions, respectively, at residues 94, 96, 101, and 113. Xenopus oocyte maturation, induced by microinjection of in vitro synthesized RNAs encoding these proteins, was scored as the percentage of microinjected stage VI oocytes that underwent GVBD. The percentage reaching GVBD represents the mean of three independent experiments.