A rice homolog of Cdk7/MO15 phosphorylates both cyclin-dependent protein kinases and the carboxy-terminal domain of RNA polymerase II

Plant J. 1998 Dec;16(5):613-9. doi: 10.1046/j.1365-313x.1998.00338.x.


The activation of cyclin-dependent protein kinases (CDKs) requires phosphorylation of a threonine residue within the T-loop by a CDK-activating kinase (CAK). The R2 protein of rice is very similar to CAKs of animals and fission yeast at the amino acid level but phosphorylation by R2 has not yet been demonstrated. When R2 was overexpressed in a CAK-deficient mutant of budding yeast, it suppressed the temperature sensitivity of the mutation. Immunoprecipitates of rice proteins with the anti-R2 antibody phosphorylated human CDK2, one of the rice CDKs (Cdc2Os1), and the carboxy-terminal domain (CTD) of the largest subunit of RNA polymerase II of Arabidopsis. Mutational analysis indicated that R2 phosphorylated the threonine residue within the T-loop of CDK2 and Cdc2Os1. R2 was found mainly in two protein complexes which had molecular masses of 190 kDa and 70 kDa, respectively, whilst the CDK- and CTD-kinase activities associated with R2 were identified in a complex of 105 kDa. These results indicate that R2 is closely related to CAKs of animals and fission yeast in terms of its phosphorylation activity and, moreover, that this CAK of rice is distinct from a CAK of the dicotyledonous plant Arabidopsis.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arabidopsis / enzymology
  • Arabidopsis / genetics
  • CDC2-CDC28 Kinases*
  • Cyclin-Dependent Kinase 2
  • Cyclin-Dependent Kinases / metabolism*
  • Enzyme Activation
  • Gene Expression
  • Genes, Plant
  • Genetic Complementation Test
  • Humans
  • Macromolecular Substances
  • Molecular Weight
  • Mutation
  • Oryza / enzymology*
  • Oryza / genetics
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • RNA Polymerase II / chemistry
  • RNA Polymerase II / metabolism*
  • Saccharomyces cerevisiae / enzymology
  • Saccharomyces cerevisiae / genetics
  • Substrate Specificity


  • Macromolecular Substances
  • Protein-Serine-Threonine Kinases
  • CDC2-CDC28 Kinases
  • CDK2 protein, human
  • Cyclin-Dependent Kinase 2
  • Cyclin-Dependent Kinases
  • cyclin-dependent kinase-activating kinase
  • RNA Polymerase II