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. 2001 Mar 27;98(8):4510–4515. doi: 10.1073/pnas.081074898

Figure 1.

Figure 1

Myc represses endogenous p21 transcription in p53-null cells in the absence of new protein synthesis. Immortalized (10.1)-MycER mouse fibroblast cells were grown to 30% confluence, and 4-HT was added for 5 h. RT-PCR was performed to examine p21 (27 cycles) and mouse S16 ribosomal protein mRNA expression (internal control). The experiment was performed under the same conditions with simultaneous addition of cycloheximide (CHX) or TSA for 12 h. Amplification of mouse p21 cDNA after addition of cycloheximide was performed for 27 cycles and after addition of TSA for 25 cycles. Typical ethidium bromide-stained 2% agarose gels with bands corresponding to p21, S16, and the 100-bp or 1-kb DNA ladders (GIBCO/BRL) are shown. (A) Myc negatively regulates p21 expression in the absence of de novo protein synthesis in vivo. (B) Myc does not recruit histone deacetylase for repression of the p21 promoter. (C) Graphs showing the results of 4–6 independent experiments described in A and B with bars indicating SD.