A BINDING-SITE FOR NUCLEAR RECEPTORS IS REQUIRED FOR THE DIFFERENTIALEXPRESSION OF THE ALDOLASE-A FAST-TWITCH MUSCLE PROMOTER IN BODY AND HEAD MUSCLES

In hind limb muscles, the aldolase A muscle-specific promoter is speci fically expressed in glycolytic fast-twitch fibers. Here, we show that in addition, it is expressed at higher levels in trunk and limb muscl es than in neck and head muscles independent of their fiber-type conte nt. Ne have identified by analysis of trans genic mice a DNA element t hat is required for this differential expression and, to a lesser exte nt, for fiber-type specificity. We show that members of the nuclear re ceptor superfamily bind this element in skeletal muscle nuclear extrac ts. Interestingly, in gel mobility shift assays, different complexes w ere formed with this sequence in tongue nuclear extracts compared with limb or trunk muscle nuclear extracts. Therefore, binding of distinct nuclear receptors to a single regulatory sequence appears to be assoc iated with the location-dependent expression of the aldolase A muscle- specific promoter.