Positive and negative regulatory DNA elements including a CCArGG box are involved in the cell type-specific expression of the human muscle dystrophin gene.

The muscle-specific promoter of the dystrophin gene is active in skeletal, cardiac, and smooth muscles and is specifically stimulated during differentiation of myoblasts into multinucleated myotubes. An 850-base pair (bp) DNA fragment upstream from the cap site is able to confer a partial muscle specificity to a reporter gene. The region between -850 and -140 bp includes nonspecific negative and positive regulatory sequences. A continuous stretch of 140 bp upstream from the cap site exhibits a striking conservation between rodents and human (93% homology) and still retains muscle preference of expression. It contains two putative binding sites for factors involved in regulation of other muscle-specific genes, a CCArGG box and an E box. This latter element, however, is unable to confer the ability to be transactivated by MyoD1 to the dystrophin promoter. The -140-bp promoter fragment exhibits antagonist effects contributed by one inhibiting sequence (nucleotide -140/-96), active in all cell types, and one activating region, from nucleotide -96 to the cap site, sufficient to confer a muscle preference of expression, in which the CCArGG box seems to play a major role.