Nuclear localization of 68 kDa calmodulin-binding protein is associated with the onset of DNA replication

J Cell Physiol. 1990 Sep;144(3):423-8. doi: 10.1002/jcp.1041440309.


In Chinese hamster embryo fibroblast cells, an increase in intracellular calmodulin levels coincided with the nuclear localization of a calmodulin-binding protein of about 68 kDa as the cells progressed from G1 to S phase. When cells were limited from entering into S phase, by omitting insulin a defined medium, intracellular CaM levels did not increase and the 68 kDa calmodulin-binding protein was completely absent from the nuclei. Corresponding to the nuclear localization of calmodulin and the 68 kDa calmodulin-binding protein in S phase cells, there was a dramatic increase in DNA polymerase and thymidine kinase activities in the nuclei of S phase cells as compared to G1 phase cells. In addition, the 68 kDa calmodulin-binding protein, along with calmodulin, is observed to be an integral component of replitase complex responsible for nuclear DNA replication in S phase cells. These observations point to the association of calmodulin and calmodulin-binding protein(s) with the replication machinery responsible for nuclear DNA replication during S phase. A possible regulatory role of these proteins in the onset of DNA replication and cell proliferation is discussed.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Batroxobin / analysis
  • Batroxobin / metabolism
  • Calmodulin / analysis
  • Calmodulin / metabolism
  • Calmodulin / physiology
  • Calmodulin-Binding Proteins / analysis*
  • Calmodulin-Binding Proteins / metabolism
  • Calmodulin-Binding Proteins / physiology
  • Cell Nucleus / analysis*
  • Cell Nucleus / ultrastructure
  • Cells, Cultured
  • Cricetinae / embryology*
  • Cricetulus / embryology*
  • DNA Replication / physiology*
  • Fibroblasts / analysis*
  • Fibroblasts / cytology
  • Fibroblasts / ultrastructure
  • Insulin / pharmacology
  • Interphase / physiology
  • Isoleucine / metabolism
  • Isoleucine / physiology


  • Calmodulin
  • Calmodulin-Binding Proteins
  • Insulin
  • Isoleucine
  • Batroxobin