Fig. 5. Determination of proteins bound to E2F derived from nuclear extracts of G₁ and preapoptotic cells. The nuclear extracts were prepared from synchronized G₁ and TGF-ß1-induced preapoptotic cells. Aliquots were mixed with a ³²P-labeled E2F-specific oligonucleotide probe and antibodies to either pRb, E2F-1, -2, or -3 (A), as well as known E2F-binding proteins, DP-1 and -2, the pRb family members p107 and p130 and the oncogene MDM2 (B). The super-shifted DNA—protein complexes were analyzed by PAGE as described in Materials and Methods. The position and numerical designation of the ³²P-labeled DNA—protein complexes are indicated on the left and right. The associated cell cycle phases of the nuclear extracts are shown at the top as well as the specific antibody used for the super-shift analysis. The numerical designations for the lanes referred to in the text are indicated at the bottom. G₁, nuclear extract from G₁ synchronized normal cells; Tß, nuclear extract from TGF-ß1 preapoptotic G₁ cells.

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