The decoy oligonucleotide approach to block the function of the transcription factor E2F. In quiescent cells (a), the factor is sequestered in a protein complex. During cell cycle progression (b), the complex is phosphorylated and free E2F is released. The factor binds to its consensus binding sequence in the promoter regions of multiple cell cycle regulatory genes. The introduction into the nucleus of decoy oligonucleotides that bear the consensus binding sequence (c) prevents interaction of the factor with its promoter targets, thus inhibiting the upregulation of cell cycle genes and blocking proliferation.