Cyclin promotes the tyrosine phosphorylation of p34cdc2 in a wee1+ dependent manner.
The regulation of p34cdc2 was investigated by overproducing p34cdc2, cyclin (A and B) and the wee1+ gene product (p107wee1) using a baculoviral expression system. p34cdc2 formed a functional complex with both cyclins as judged by co-precipitation, phosphorylation of cyclin in vitro, and activation of p34cdc2 histone H1 kinase activity. Co-production of p34cdc2 and p107wee1 in insect cells resulted in a minor population of p34cdc2 that was phosphorylated on tyrosine and displayed an altered electrophoretic mobility. When p34cdc2 and p107wee1 were co-produced with cyclin (A or B) in insect cells, there was a dramatic increase in the population of p34cdc2 that was phosphorylated on tyrosine and that displayed a shift in electrophoretic mobility. The phosphorylation of p34cdc2 on tyrosine was absolutely dependent upon the presence of kinase-active p107wee1. Tyrosine-specific as well as serine/threonine-specific protein kinase activities co-immunoprecipitated with p107wee1. These results suggest that cyclin functions to facilitate tyrosine phosphorylation of p34cdc2 and that p107wee1 functions to regulate p34cdc2, either directly or indirectly, by tyrosine phosphorylation.
Parker
L L
LL
Department of Physiology, Tufts University School of Medicine, Boston, MA 02111.
Atherton-Fessler
S
S
Lee
M S
MS
Ogg
S
S
Falk
J L
JL
Swenson
K I
KI
Piwnica-Worms
H
H
D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D016203:CDC2 Protein Kinase / Q000235:genetics* / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D018797:Cell Cycle Proteins; D016213:Cyclins / Q000235:genetics*; D006801:Humans; D009036:Moths / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D011505:Protein-Tyrosine Kinases; D012568:Schizosaccharomyces / Q000201:enzymology; D029702:Schizosaccharomyces pombe Proteins; D014443:Tyrosine / Q000378:metabolism*; D014638:Vanadates / Q000378:metabolism
D018797:Cell Cycle Proteins; D016213:Cyclins; D009687:Nuclear Proteins; D029702:Schizosaccharomyces pombe Proteins; D014638:Vanadates; D014443:Tyrosine; D011494:Protein Kinases; C068689:wee1 protein, S pombe; D011505:Protein-Tyrosine Kinases; C499349:WEE1 protein, human; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D016203:CDC2 Protein Kinase