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The molecular basis for a cytosolic malic enzyme null mutation malic enzyme messenger rna from mod 1 null mice contains an internal in frame duplication that extends the coding sequence by 522 nucleotides


, : The molecular basis for a cytosolic malic enzyme null mutation malic enzyme messenger rna from mod 1 null mice contains an internal in frame duplication that extends the coding sequence by 522 nucleotides. Journal of Biological Chemistry 263(9): 4494-4499

Many tissues from wild type mice express cytosolic malic enzyme activity and contain two mRNAs (2.0 and 3.1 kilobases (kb)) that encode a single 64-kDa malic enzyme subunit polypeptide. MOD-1 null mutant mice lack cytosolic malic enzyme activity but express 2.5- and 3.6-kb mRNAs that hybridize with wild type malic enzyme cDNAs and are induced in liver by a starvation/carbohydrate refeeding regimen. To investigate the basis of the MOD-1 null mutation, a .lambda.gt11 cDNA library was constructed using mRNA from the livers of induced MOD-1 null mice as a template. A recombinant phage with a 2-kb insert was isolated by screening with wild type malic enzyme cDNA probes. The subcloned insert exhibited an atypical (non-wild type) restriction pattern and was subjected to sequence analysis. MOD-1 null malic enzyme cDNA contains an internal tandemly duplicated sequence that corresponds to nucleotides 1027-1548 in the coding region of wild type murine malic enzyme cDNA (Bagchi, S., Wise, L.S., Brown, M.L., Bregman, D., Sul, H.S., and Rubin, C.S. (1987) J. Biol. Chem. 262, 1558-1565). An open reading frame is retained throughout the duplicated sequence. The discovery of a 522-nucleotide in-frame duplication accounts for the increased size of MOD-1 null malic enzyme mRNAs and suggest that a variant malic enzyme polypeptide that is 19 kDa larger than the wild type subunit might be found in mutant mice. Western immunoblot analysis disclosed that MOD-1 null liver cytosol contains an 82-kDa protein that is recognized by anti-malic enzyme antibodies. Under stringent conditions, an anti-sense 32P-oligonucleotide that spans the abnormal junction between the reiterated sequences hybridized with the 2.5 and 3.6-kb MOD-1 null malic enzyme mRNAs but failed to form stable complexes with wild type malic enzyme mRNAs. Thus, both MOD-1 null malic enzyme mRNAS contain the duplication deduced from cDNA sequence analyses. The MOD-1 null mutation might originate from an unequal crossover between homologous regions of two different introns in the malic enzyme gene, thereby causing the duplication of one or more exons.


Accession: 006719788

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Related references

Brown, M.L.; Wise, L.S.; Rubin, C.S., 1988: The molecular basis for a cytosolic malic enzyme null mutation. Malic enzyme mRNA from MOD-1 null mice contains an internal in-frame duplication that extends the coding sequence by 522 nucleotides. Many tissues from wild-type mice express cytosolic malic enzyme activity and contain two mRNAs (2.0 and 3.1 kb) that encode a single 64-kilodalton malic enzyme subunit polypeptide. Mice with the Mod-1 null allele lack cytosolic malic enzyme activi...

Sul H.S.; Wise L.S.; Brown M.L.; Rubin C.S., 1984: Cloning of complementary dna sequences from murine malic enzyme and the identification of aberrantly large malic enzyme messenger rna in mod 1 null mice. Polysomes containing cytosolic malic enzyme mRNA and malic enzyme nascent chains were complexed with specific antibodies and purified by chromatography on protein A-Sepharose. When poly(A+) mRNA derived from the immunoselected polysomes was transl...

Brown M.L.; Wise L.S.; Rubin C.S., 1987: Molecular basis for a malic enzyme null mutation. Federation Proceedings 46(6): 2014

Sul, H.S.; Wise, L.S.; Brown, M.L.; Rubin, C.S., 1984: Cloning of cDNA sequences for murine malic enzyme and the identification of aberrantly large malic enzyme mRNA in MOD-1 null mice. Polysomes containing cytosolic malic enzyme mRNA and malic enzyme nascent chains were complexed with specific antibodies and purified by chromatography on protein A-Sepharose. When poly(A+) mRNA derived from the immunoselected polysomes was transl...

Strait K.A.; Kinlaw W.B.; Mariash C.N.; Oppenheimer J.H., 1989: Kinetics of induction by thyroid hormone of the two hepatic messenger rna coding for cytosolic malic enzyme in the hypothyroid and euthyroid states evidence against an obligatory role of s14 protein in malic enzyme gene expression. In rat liver, triiodothyronine (T3) and dietary carbohydrate induce the expression of the genes coding for malic enzyme (ME) (EC 1.1.1.40) and S14 protein. The mRNAs for both ME and S14 are elevated under circumstances associated with augmented li...

Glynias, M.J.; Morris, S.M.J. ; Fantozzi, D.A.; Winberry, L.K.; Back, D.W.; Fisch, J.E.; Goodridge, A.G., 1984: A cloned complementary dna for duck malic enzyme detects abnormally large malic enzyme ec 1.1.1.40 messenger rna species in a strain of mice mod 1n that does not express malic enzyme protein. 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 fe...

Lee, C.Y.; Chasalow, F.; Lee, S.M.; Lewis, S.; Johnson, F.M., 1980: A null mutation of cytoplasmic malic enzyme in mice. Molecular and Cellular Biochemistry 30(3): 143-149

Lee, C.Y.; Chasalow, F.; Lee, S.M.; Lewis, S.; Johnson, F.M., 1980: A null mutation of cytoplasmic malic enzyme ec 1.1.1.40 in mice. In the course of conducting a biochemical screening program for mutant enzymes in mice, individuals with an apparent nonfunctional allele at the locus (Mod-1) responsible for cytoplasmic malic enzyme (EC 1.1.1.40) were observed. The variant, later...

Magnuson, M.A.; Nikodem, V.M., 1983: Molecular cloning of a complementary dna sequence for rat malic enzyme ec 1.1.1.40 direct evidence for induction in vivo of rat liver malic enzyme messenger rna by thyroid hormone. Malic enzyme mRNA was partially purified to 12% of total mRNA activity (> 150-fold enrichment) from 3-5-3'-triiodo-L-thyronine-carbohydrate-stimulated rat liver by polysome immunopurification followed by oligo(dT)-cellulose chromatography....

Strait, K.A.; Kinlaw, W.B.; Mariash, C.N.; Oppenheimer, J.H., 1989: Kinetics of induction by thyroid hormone of the two hepatic mRNAs coding for cytosolic malic enzyme in the hypothyroid and euthyroid states. Evidence against an obligatory role of S14 protein in malic enzyme gene expression. In rat liver, triiodothyronine (T3) and dietary carbohydrate induce the expression of the genes coding for malic enzyme (ME) (EC 1.1.1.40) and S14 protein. The mRNAs for both ME and S14 are elevated under circumstances associated with augmented li...