Structure, turnover, and heme-mediated suppression of the level of mRNA encoding rat liver delta-aminolevulinate synthase.
lambda gt11 cDNA libraries were constructed with poly(A)+ RNA preparations from both porphyric chicken and rat livers. A cDNA which encodes chicken hepatic delta-aminolevulinate synthase was cloned by screening with an anti-chicken liver delta-aminolevulinate synthase antibody. Using this cDNA as a probe, cDNAs encoding the entire protein coding sequence of rat hepatic delta-aminolevulinate synthase were then cloned. The complete nucleotide sequences of the cDNAs have been determined. The result predicts that the rat hepatic pre-delta-aminolevulinate synthase comprises 642 amino acids. We measured the half-life of the hepatic delta-aminolevulinate synthase mRNA by RNA blot hybridization analysis using allylisopropylacetamide-induced porphyric rats as an experimental model and the rat cDNA as a hybridization probe. The half-life of the mRNA determined by the injection of alpha-amanitin is as short as 20 min. This value is significantly shorter than the estimated half-lives of most other mRNAs in the differentiated tissues of animals. The effect of hemin administration on the level of hepatic delta-amino-levulinate synthase mRNA was also examined. The half-disappearance time of the mRNA after the hemin administration was essentially the same as that determined by alpha-amanitin or actinomycin D, and no additive effect was observed between alpha-amanitin and hemin on the half-life determination. The results provide convincing evidence that heme inhibits the transcription of delta-aminolevulinate synthase mRNA.
Yamamoto
M
M
Department of Biochemistry, Toyama Medical and Pharmaceutical University School of Medicine, Japan.
Kure
S
S
Engel
J D
JD
Hiraga
K
K
D000624:5-Aminolevulinate Synthetase / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D005796:Genes / Q000187:drug effects*; D006418:Heme / Q000494:pharmacology*; D008099:Liver / Q000201:enzymology*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D013489:Suppression, Genetic / Q000187:drug effects*
D012333:RNA, Messenger; D006418:Heme; D000624:5-Aminolevulinate Synthetase