FIG. 7.
Activation of Id3 and NP1 gene expression is directly dependent on the MyoD-ER protein in 10T1/2-MyoD-ER cells. 10T1/2-MyoD-ER cells were maintained in control GM or GM containing β-estradiol with or without cycloheximide (CHX) to inhibit protein synthesis. Northern blot hybridizations reveal that Id3 and NP1 transcripts are only detected in 10T1/2-MyoD-ER cells treated with β-estradiol. Cells provided cycloheximide also accumulate high levels of Id3 and NP1 transcripts, even in the absence of new protein synthesis. These results suggest that MyoD directly activates expression of the Id3 and NP1 genes in this model system. EtOH, ethanol; nt, nucleotides.