The existence of two distinct Wee1 isoforms in Xenopus: implications for the developmental regulation of the cell cycle.
In eukaryotic cells, the Wee1 protein kinase phosphorylates and inhibits Cdc2, thereby creating an interphase of the cell cycle. In Xenopus, the conventional Wee1 homolog (termed Xe-Wee1A, or Wee1A for short) is maternally expressed and functions in pregastrula embryos with rapid cell cycles. Here, we have isolated a second, zygotic isoform of Xenopus Wee1, termed Xe-Wee1B (or Wee1B for short), that is expressed in postgastrula embryos and various adult tissues. When ectopically expressed in immature oocytes, Wee1B inhibits Cdc2 activity and oocyte maturation (or entry into M phase) much more strongly than Wee1A, due to its short C-terminal regulatory domain. Moreover, ectopic Wee1B, unlike Wee1A, is very labile during meiosis II and cannot accumulate in mature oocytes due to the presence of PEST-like sequences in its N-terminal regulatory domain. Finally, when expressed in fertilized eggs, ectopic Wee1B but not Wee1A does affect cell division and impair cell viability in early embryos, due primarily to its very strong kinase activity. These results suggest strongly that the differential expression of Wee1A and Wee1B is crucial for the developmental regulation of the cell cycle in Xenopus.
Okamoto
Kengo
K
Department of Biology, Graduate School of Sciences, Kyushu University, Hakozaki 6-10-1, Fukuoka 812-8581, Japan.
Nakajo
Nobushige
N
Sagata
Noriyuki
N
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins; D018507:Gene Expression Regulation, Developmental; D014644:Genetic Variation; D008540:Meiosis; D008938:Mitosis; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism; D010802:Phylogeny; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014981:Xenopus / Q000235:genetics / Q000254:growth & development*; D029867:Xenopus Proteins
D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D020033:Protein Isoforms; D029867:Xenopus Proteins; C530005:WEE1 protein, Xenopus; C466028:Wee2 protein, Xenopus; D011505:Protein-Tyrosine Kinases