Figure 4.

The effect of differentiation on transcription factor binding. Nuclear extracts from undifferentiated F9 cells (lanes 1, 3, 4, 9, 11, and 12) and from F9 cells after the induction of differentiation (lanes 2, 5, 6, 10, 13, and 14) were incubated with ³²P-labeled oligonucleotide corresponding to position −177 to −146 (oligo-1) or with ³²P-labeled oligonucleotide corresponding to position 32–58 (oligo-2) of the hTERT promoter. Incubation was performed with or without a competitor (150-fold excess of cold oligonucleotide) as indicated. As a control, a nuclear extract from telomerase-negative NHF cells was used (lanes 7 and 15). In addition, c-Myc in vitro transcription–translation product was used to examine binding to the oligo-1 E-box motif (lane 8). Arrowheads indicate specific retarded bands.