Fig. 3.

Mutation of the E-box sequence in the mouse δ-promoter suppresses activity-dependent regulation. Schematic representation of the mouse δ −1823/+25 promoter is shown. Putative transcription factor binding sites within 100 bp upstream of the transcription start site are shown. Expression of injected δ −1823/+25 pXP or δ −1823/+25 E1 mutation 5 pXP in innervated and denervated muscle relative to the wild-type construct, along with the fold difference, is indicated to the right of the constructs. Numbers in parenthesis indicate number of animals injected. Luc light units were normalized to co-injected CMVCAT activity. p-values (shown in brackets) were calculated using a one-tailed t test. Putative regulatory elements are indicated by rectangles along the sequence and labeled at the bottom of the figure. The E-box element in δ −1823 E1 mut 5 is black to indicate that it was mutated. The enhancer X is a previously identified enhancer with no homology to known regulatory elements (W. Walke and D. Goldman, unpublished observations) (Simon and Burden, 1993).