Speedy: a novel cell cycle regulator of the G2/M transition.
Stage VI Xenopus oocytes are suspended at the G2/M transition of meiosis I, and represent an excellent system for the identification and examination of cell cycle regulatory proteins. Essential cell cycle regulators such as MAPK, cyclins and mos have the ability to induce oocyte maturation, causing the resumption of the cell cycle from its arrested state. We have identified the product of a novel Xenopus gene, Speedy or Spy1, which is able to induce rapid maturation of Xenopus oocytes, resulting in the induction of germinal vesicle breakdown (GVBD) and activation of M-phasepromoting factor (MPF). Spy1 activates the MAPK pathway in oocytes, and its ability to induce maturation is dependent upon this pathway. Spy1-induced maturation occurs much more rapidly than maturation induced by other cell cycle regulators including progesterone, mos or Ras, and does not require any of these proteins or hormones, indicating that Spy1-induced maturation proceeds through a novel regulatory pathway. In addition, we have shown that Spy1 physically interacts with cdk2, and prematurely activates cdk2 kinase activity. Spy1 therefore represents a novel cell cycle regulatory protein, inducing maturation through the activation of MAPK and MPF, and also leading to the premature activation of cdk2.
Lenormand
J L
JL
Department of Chemistry and Biochemistry, Center for Molecular Genetics, University of California, San Diego, La Jolla, CA 92093-0367, USA.
Dellinger
R W
RW
Knudsen
K E
KE
Subramani
S
S
Donoghue
D J
DJ
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D042846:CDC2-CDC28 Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000502:physiology*; D003001:Cloning, Molecular; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D016195:G2 Phase / Q000235:genetics* / Q000502:physiology*; D018816:Genes, cdc; D008938:Mitosis / Q000235:genetics* / Q000502:physiology*; D008969:Molecular Sequence Data; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011836:Radiation Tolerance / Q000235:genetics; D012568:Schizosaccharomyces / Q000235:genetics / Q000528:radiation effects; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D014981:Xenopus; D029867:Xenopus Proteins
D018797:Cell Cycle Proteins; D017931:DNA Primers; D018076:DNA, Complementary; D029867:Xenopus Proteins; C119055:ls27 protein, Xenopus; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D042846:CDC2-CDC28 Kinases; C495891:Cdk2 protein, Xenopus; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases