cdc25+ encodes a protein phosphatase that dephosphorylates p34cdc2.
To determine how the human cdc25 gene product acts to regulate p34cdc2 at the G2 to M transition, we have overproduced the full-length protein (cdc25Hs) as well as several deletion mutants in bacteria as glutathione-S-transferase fusion proteins. The wild-type cdc25Hs gene product was synthesized as an 80-kDa fusion protein (p80GST-cdc25) and was judged to be functional by several criteria: recombinant p80GST-cdc25 induced meiotic maturation of Xenopus oocytes in the presence of cycloheximide; p80GST-cdc25 activated histone H1 kinase activity upon addition to extracts prepared from Xenopus oocytes; p80GST-cdc25 activated p34cdc2/cyclin B complexes (prematuration promoting factor) in immune complex kinase assays performed in vitro; p80GST-cdc25 stimulated the tyrosine dephosphorylation of p34cdc2/cyclin complexes isolated from Xenopus oocyte extracts as well as from overproducing insect cells; and p80GST-cdc25 hydrolyzed p-nitrophenylphosphate. In addition, deletion analysis defined a functional domain residing within the carboxy-terminus of the cdc25Hs protein. Taken together, these results suggest that the cdc25Hs protein is itself a phosphatase and that it may function directly in the tyrosine dephosphorylation and activation of p34cdc2 at the G2 to M transition.
Lee
M S
MS
Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111.
Ogg
S
S
Xu
M
M
Parker
L L
LL
Donoghue
D J
DJ
Maller
J L
JL
Piwnica-Worms
H
H
D000818:Animals; D001483:Base Sequence; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D002460:Cell Line; D005982:Glutathione Transferase / Q000378:metabolism; D016200:Maturation-Promoting Factor / Q000502:physiology; D008540:Meiosis; D008969:Molecular Sequence Data; D009596:Nitrophenols / Q000378:metabolism; D009865:Oocytes / Q000502:physiology; D009943:Organophosphorus Compounds / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D014981:Xenopus; D020687:cdc25 Phosphatases
D009596:Nitrophenols; D009943:Organophosphorus Compounds; D011506:Proteins; D011993:Recombinant Fusion Proteins; C008644:nitrophenylphosphate; D014443:Tyrosine; D005982:Glutathione Transferase; D016203:CDC2 Protein Kinase; D016200:Maturation-Promoting Factor; D010749:Phosphoprotein Phosphatases; D020687:cdc25 Phosphatases