High resolution

Module 4: Figure Myc as a gene activator



Myc activation of target genes that function in cell proliferation.

There are a large number of Myc target genes that are activated by an increase in the level of Myc. Many of these Myc targets have an E-box element containing the 5'-CACGTG-3' sequence. In quiescent G0 or differentiated cells, the many Myc target genes are repressed by Max/Mad or Max/Mnt dimers, together with the SIN3/HDAC transcriptional co-repressor complex. The HDACs deacetylate chromatin, making it inaccessible to transcription. Myc activates transcription by replacing the Mad/Mnt, which removes the repressor complex. The Myc/Max dimer bind to the E-box and provides a complex to bring in various coactivators. The histone acetyltransferases (HATs), such as CBP/p300, CGN5 and TIP60, acetylate histones to open up the chromatin to make it accessible so that the Myc target genes can be transcribed. These target genes contribute to cell growth and activation of the cell cycle.