A novel fatty acid response element controls the expression of the flight muscle FABP gene of the desert locust, Schistocerca gregaria

In many tissues, fatty acid binding protein (FABP) expression is stimulated by exposure to elevated fatty acid levels. In contrast to the FABP genes e xpressed in other tissues, the molecular mechanisms that mediate the upregu lation of the muscle FABP gene have not been elucidated. We have studied th e expression of locust flight muscle FABP, a protein that is highly homolog ous to the mammalian H-FABPs. A 130-bp promoter fragment of the locust gene , which includes a canonical TATA box and several GC boxes, is sufficient f or the transcription of a reporter gene in mammalian L6 myoblasts. Twofold higher expression rates are observed when the promoter contains 280 bp or m ore of upstream sequence. Treatment of myoblasts with various fatty acids l eads to a marked increase of expression in the longer constructs, but not i n the minimal promoter. We have identified a 19-bp inverted repeat (-162/-1 80) as the element responsible for the fatty acid-mediated induction of gen e expression. Deletion of this element eliminates the fatty acid response, and gel shift analysis demonstrates specific binding to nuclear proteins fr om both L6 myoblasts and locust flight muscle cells. This fatty acid respon se element bears no similarity to any known transcription factor binding si te. A similar palindrome was also found in the promoter of the Drosophila m elanogaster muscle FABP gene, and in reverse orientation upstream of all ma mmalian heart FABP genes. Given the structural and functional conservation of muscle FABPs and their genes, it is possible that this fatty acid respon se element also modulates the expression of the mammalian H-FABP genes.