Changes in in vivo protein-DNA interactions occur at the c-myc P2 promoter during differentiation.

Down regulation of the c-myc gene is a prerequisite for the differentiation of a number of cell types. Studies have shown that two mechanisms of inactivation are involved in c-myc repression: a block of the elongation of RNA polymerase followed by transcriptional inactivation mediated through promoter sequences. In this study DMS in vivo footprinting was performed on the P2 promoter region of c-myc in differentiated and undifferentiated HL60 cells. A differentiation-specific footprint was observed at G residues immediately upstream of the TATA box. This observation occurred only in cells differentiated for 48 hours or more and hence is likely to be involved in the repression of c-myc by promoter inactivation.