The repression of beta-isopropylmalate dehydrogenase, the LEU2 gene product, by leucine and leucine plus threonine was unaffected by the transposition of LEU2 from its original locus on chromosome III to a new locus within the ribosomal deoxyribonucleic acid gene cluster on chromosome XII. Since the expression of the LEU2 gene is probably controlled at a pretranslational level, we conclude that the recombinant plasmid used for transformation carries regulatory information in addition to LEU2 structural information.