Heme regulates the expression in Saccharomyces cerevisiae of chimaeric genes containing 5'-flanking soybean leghemoglobin sequences.

The TM1 yeast mutant was transformed with a 2 micron-derived plasmid (YEp24) which carries a chimaeric gene containing the Escherichia coli chloramphenicol acetyl transferase (CAT) gene fused to the 5'- and 3'-flanking regions of the soybean leghemoglobin (Lb) c3 gene. Expression of the chimaeric CAT gene is controlled specifically by heme at a post-transcriptional level, most likely by regulating the efficiencies of translation. Expression of another chimaeric gene consisting of the neomycin phosphotransferase (NPTII) gene fused to only the 5'-flanking region of the Lbc3 gene is regulated by heme in a similar way. Thus, in yeast, heme modulates the translation of the chimaeric mRNAs through interactions with the 5' Lbc3 non-coding region.