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In vertebrate and invertebrate muscles, the expression of fatty acid binding proteins ( FABP) is induced by long chain fatty acids. To identify the fatty acid response elements that mediate this up-regulation, the gene of the FABP expressed in locust flight muscle was cloned, and its upstream sequences analyzed for potential regulatory elements. Comparison with other muscle FABP promoters revealed the presence of a 19-bp imperfect inverted repeat sequence that contains two hexanucleotide half sites (AGTGGT and ATGGGA), interspersed by 3 nucleotides. The promoter activity was studied with reporter gene constructs in L6 myoblasts, in which H-FABP expression is stimulated by long-chain fatty acids in a similar manner as in adult cardiomyocytes. The 19 bp element, located 180 bp upstream of the transcription start site, was found to be essential for the fatty acid induction of gene expression, and gel shift analysis confirmed that this fatty acid response element is capable of binding nuclear proteins both from rat myoblasts and locust muscle in the presence of fatty acids. A similar, but reverse sequence that is present upstream of all mammalian H-FABP promoters may modulate the expression of the rat H-FABP gene.