MOLECULAR GENETICS OF HEME BIOSYNTHETIC ENZYMES

我们对血红素代谢及其扰动了解甚多，但知之甚少

Much is known about heme metabolism and its perturbations, little is known of the molecular mechanisms by which the production of this essential material is regulated. Our goals are to delineate such mechanisms with respect to the expression of the first two enzymes in the heme biosynthetic pathway: delta-aminolevulinate synthase (ALAS) and delta-aminolevulinate dehydrase (ALAD). To this undertaking, we bring verified rat liver ALAD-cDNA clones and monoclonal antibodies developed against rat liver ALAD and ALAS. Seven specific aims are set: first, isolation and characterization of full-length mouse and rat ALAD-cDNA; second, isolation and delineation of ALAD genomic sequences in both species; third, verification of our finding that differences in ALAD-gene dosage account for incremental differences in ALAD enzymatic activity between inbred mouse strains; fourth, assessment of (a) genetic polymorphism for ALAD-gene copy number in outcrossed and feral mice and (b) its possible relationship to environmental lead; fifth, delineation of the molecular nature of ALAD in settings where it is atypical, e.g., erythroleukemia K562 cells, fetal liver and human mutants; sixth, isolation of full-length ALAS-cDNA and corresponding gene DNA from rat and mouse liver; and seventh, application of ALAS- and ALAD-probes to the dissection of molecular mechanisms underlying rapid flux of enzyme expression in murine erythroleukemia cells, in murine erythroid progenitors, and in the livers of animals treated with porphyrinogenic agents.