Dominant negative E2F inhibits progression of the cell cycle after the midblastula transition in Xenopus

Cell Struct Funct. 2003 Dec;28(6):515-22. doi: 10.1247/csf.28.515.


The cleavage cycle, which is initiated by fertilization, consists of only S and M phases, and the gap phases (G1 and G2) appear after the midblastula transition (MBT) in the African clawed frog, Xenopus laevis. During early development in Xenopus, we examined the E2F activity, which controls transition from the G1 to S phase in the somatic cell cycle. Gel retardation and transactivation assays revealed that, although the E2F protein was constantly present throughout early development, the E2F transactivation activity was induced in a stage-specific manner, that is, low before MBT and rapidly increased after MBT. Introduction of the recombinant dominant negative E2F (dnE2F), but not the control, protein into the 2-cell stage embryos specifically suppressed E2F activation after MBT. Cells in dnE2F-injected embryos appeared normal before MBT, but ceased to proliferate and eventually died at the gastrula. These cells contained decreased cdk activity with enhanced inhibitory phosphorylation of Cdc2 at Tyr15. Thus, E2F activity is required for cell cycle progression and cell viability after MBT, but not essential for MBT transition and developmental progression during the cleavage stage.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blastula / cytology
  • Blastula / physiology*
  • CDC2 Protein Kinase / metabolism
  • Cell Cycle / physiology*
  • Cell Cycle Proteins / genetics*
  • Cell Cycle Proteins / metabolism*
  • DNA-Binding Proteins / genetics*
  • DNA-Binding Proteins / metabolism*
  • E2F Transcription Factors
  • Embryo, Nonmammalian / cytology
  • Embryo, Nonmammalian / physiology
  • Gastrula / metabolism
  • Gene Expression Regulation, Developmental
  • Genes, Dominant / genetics
  • Humans
  • Phosphorylation
  • Protein Structure, Tertiary / genetics
  • Transcription Factors / genetics*
  • Transcription Factors / metabolism*
  • Transcriptional Activation
  • Tyrosine / metabolism
  • Xenopus laevis / embryology*
  • Xenopus laevis / physiology


  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • E2F Transcription Factors
  • Transcription Factors
  • Tyrosine
  • CDC2 Protein Kinase