Interaction of nuclear factors with the upstream region of the alpha-subunit gene of chicken muscle acetylcholine receptor: variations with muscle differentiation and denervation.

The region lying between nucleotides (nt) -110 and -45 of chicken acetylcholine receptor alpha-subunit gene 5' upstream sequence confers developmental control of expression in primary cultures of chicken myotubes. This region interacts with several nuclear factors present in muscle cells as shown by DNase I footprinting and gel-retardation experiments. An Sp1-like factor and a guanine stretch-binding protein were found to bind to overlapping sites immediately upstream of the TATA box. Several factors interacting in the same region with a domain similar to the SV40 enhancer core appeared during in vitro differentiation of myoblasts into myotubes. The concentration of some of these factors increased also after denervation of leg muscle in newborn chickens. The specific interaction of nuclear factors with this domain may thus play a critical role in the regulation of alpha-subunit gene expression by muscle differentiation and electrical activity.