Cyclin promotes the tyrosine phosphorylation of p34cdc2 in a wee1+ dependent manner

EMBO J. 1991 May;10(5):1255-63.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Baculoviridae / genetics
  • CDC2 Protein Kinase / genetics*
  • CDC2 Protein Kinase / metabolism
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Cell Cycle Proteins*
  • Cyclins / genetics*
  • Humans
  • Moths / genetics
  • Mutagenesis, Site-Directed
  • Nuclear Proteins*
  • Phosphorylation
  • Protein Kinases / genetics*
  • Protein Kinases / metabolism
  • Protein-Tyrosine Kinases*
  • Schizosaccharomyces / enzymology
  • Schizosaccharomyces pombe Proteins
  • Tyrosine / metabolism*
  • Vanadates / metabolism


  • Cell Cycle Proteins
  • Cyclins
  • Nuclear Proteins
  • Schizosaccharomyces pombe Proteins
  • Vanadates
  • Tyrosine
  • Protein Kinases
  • wee1 protein, S pombe
  • Protein-Tyrosine Kinases
  • WEE1 protein, human
  • Calcium-Calmodulin-Dependent Protein Kinases
  • CDC2 Protein Kinase