Function of the c-Myc oncoprotein in chromatin remodeling and transcription.

Deregulated expression of the c-myc proto-oncogene contributes to malignant progression of a variety of tumors. The c-Myc protein (or Myc) is a transcription factor that positively or negatively regulates expression of distinct sets of target genes. Transcriptional activation by Myc is mediated through dimerization with Max and binding to the DNA consensus sequence CA(C/T)GTG (the E-box). Transcriptional inhibition is mediated through distinct DNA elements, and may be due to functional interference with factors that transactivate via these sequences. We review here our current knowledge on these transcriptional activities of Myc and their relationship to its biological function. The findings that Myc interacts with subunits of histone acetyl-transferase (HAT) complexes and of the ATP-dependent chromatin remodeling complex, SWI/SNF, suggest that localized changes in chromatin structure may mediate Myc function. We present a working hypothesis for the concerted action of HAT and SWI/SNF complexes in Myc-activated transcription and argue that this model should prompt re-thinking of the experimental strategies and criteria used to identify Myc target genes.