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Human cyclin K, a novel RNA polymerase II-associated cyclin possessing both carboxy-terminal domain kinase and Cdk-activating kinase activity.

The gene coding for human cyclin K was isolated as a CPR (cell-cycle progression restoration) gene by virtue of its ability to impart a Far- phenotype to the budding yeast Saccharomyces cerevisiae and to rescue the lethality of a deletion of the G1 cyclin genes CLN1, CLN2, and CLN3. The cyclin K gene encodes a 357-amino-acid protein most closely related to human cyclins C and H, which have been proposed to play a role in regulating basal transcription through their association with and activation of cyclin-dependent kinases (Cdks) that phosphorylate the carboxyl-terminal domain (CTD) of the large subunit of RNA polymerase II (RNAP II). Murine and Drosophila melanogaster homologs of cyclin K have also been identified. Cyclin K mRNA is ubiquitously expressed in adult mouse and human tissues, but is most abundant in the developing germ cells of the adult testis and ovaries. Cyclin K is associated with potent CTD kinase and Cdk kinase (CAK) activity in vitro and coimmunoprecipitates with the large subunit of RNAP II. Thus, cyclin K represents a new member of the "transcription" cyclin family which may play a dual role in regulating Cdk and RNAP II activity.

Pubmed ID: 9632813


  • Edwards MC
  • Wong C
  • Elledge SJ


Molecular and cellular biology

Publication Data

July 16, 1998

Associated Grants

  • Agency: NIGMS NIH HHS, Id: GM44664

Mesh Terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • CDC2 Protein Kinase
  • Cell Line
  • Coenzymes
  • Cyclin-Dependent Kinase 8
  • Cyclin-Dependent Kinases
  • Cyclins
  • Drosophila Proteins
  • Drosophila melanogaster
  • G1 Phase
  • Glutathione Transferase
  • Humans
  • Insects
  • Mice
  • Mice, Inbred C57BL
  • Molecular Sequence Data
  • Phenotype
  • Protein Kinases
  • Protein-Serine-Threonine Kinases
  • RNA Polymerase II
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Sequence Homology, Amino Acid
  • Ubiquitins