Akt inhibits Myt1 in the signalling pathway that leads to meiotic G2/M-phase transition.
In eukaryotes, entry into M-phase of the cell cycle is induced by activation of cyclin B-Cdc2 kinase. At G2-phase, the activity of its inactivator, a member of the Wee1 family of protein kinases, exceeds that of its activator, Cdc25C phosphatase. However, at M-phase entry the situation is reversed, such that the activity of Cdc25C exceeds that of the Wee1 family. The mechanism of this reversal is unclear. Here we show that in oocytes from the starfish Asterina pectinifera, the kinase Akt (or protein kinase B (PKB)) phosphorylates and downregulates Myt1, a member of the Wee1 family. This switches the balance of regulator activities and causes the initial activation of cyclin B-Cdc2 at the meiotic G2/M-phase transition. These findings identify Myt1 as a new target of Akt, and demonstrate that Akt functions as an M-phase initiator.
Okumura
Eiichi
E
Laboratory of Cell and Developmental Biology, Graduate School of Bioscience, Tokyo Institute of Technology, Nagatsuta, Midoriku, Yokohama 226-8501, Japan.
Fukuhara
Takeshi
T
Yoshida
Hitoshi
H
Hanada Si
Shin-ichiro
S
Kozutsumi
Rie
R
Mori
Masashi
M
Tachibana
Kazunori
K
Kishimoto
Takeo
T
D000595:Amino Acid Sequence; D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D004789:Enzyme Activation; D008540:Meiosis / Q000502:physiology*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology*; D013215:Starfish / Q000502:physiology
D019926:Cyclin B; D011518:Proto-Oncogene Proteins; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D016203:CDC2 Protein Kinase