Fig. 2.

Comparison between physiological Myc and deregulated Myc. The collapsed control of Myc intensifies the expression of both target genes as well as additional aberrant nontarget genes, thereby enhancing tumorigenesis. In the physiological state, Myc is tightly controlled by transcriptional as well as post-transcriptional components. High-affinity target genes, with expression independent of the Myc level and cell types, actively respond to Myc, while low-affinity target genes respond at a low level. The integrated signals from these two target genes facilitate the cells to thrive. Decontrolled Myc increases the expression of both high- and low- affinity target genes; also, additional nontarget genes might be activated. These three signals lead to further tumorigenesis