title: A cloned cDNA for duck malic enzyme detects abnormally large malic enzyme mRNAs in a strain of mice (Mod-1n) that does not express malic enzyme protein.
abstract: Sensitive immunochemical assays were used to measure the mass and rate of synthesis of malic enzyme protein in wild-type and Mod-1n mutant mice fed a high carbohydrate/low fat diet supplemented with thyroid hormone. Malic enzyme activity in the fed, wild-type mice was 100-fold higher than in starved, wild-type mice. Neither activity, mass, nor synthesis of malic enzyme could be detected in fed, mutant mice. However, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase responded to these dietary manipulations with normal or supranormal increases in activities, respectively, in mutant mice. A cDNA clone containing an almost complete copy of the mRNA for malic enzyme from duck liver was used to analyze poly(A+) RNA from C57BL/6J-DBA/2J hybrid mice that had been fasted and refed a high carbohydrate/low fat diet supplemented with thyroid hormone. The 32P-cDNA probe hybridized to two RNAs of 2250 and 2950 nucleotides. The same two RNAs were detected in RNA from starved mice except at much lower concentrations. A similar analysis of RNA from Mod-1n mice fed the high carbohydrate-thyroid diet also revealed two hybridizing RNAs but each was 700-800 nucleotides longer than its counterpart in wild-type mice. The abundance of malic enzyme mRNA in the fed, mutant mice was about the same as that in fed, wild-type mice. The mutant malic enzyme mRNAs also were present in RNA from starved mice but at much lower concentrations. These results suggest that the mutation responsible for the Mod-1n phenotype is in the structural gene for malic enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D003001:Cloning, Molecular; D003433:Crosses, Genetic; D004247:DNA / Q000378:metabolism*; D004372:Ducks / Q000235:genetics*; D008099:Liver / Q000201:enzymology; D008291:Malate Dehydrogenase / Q000235:genetics*; D051379:Mice; D008815:Mice, Inbred Strains; D008817:Mice, Mutant Strains / Q000235:genetics*; D008970:Molecular Weight; D012333:RNA, Messenger / Q000235:genetics*; D013045:Species Specificity
chemical_list: D012333:RNA, Messenger; D004247:DNA; D008291:Malate Dehydrogenase