Abstract
We have recently reported that the human apolipoprotein A-I (apoA-I) and apolipoprotein C-III (apoC-III) genes are physically linked and that the presence of a DNA insertion in the apoA-I gene is correlated with apoA-I-apoC-III deficiency in patients with premature atherosclerosis. In addition, the presence of a polymorphic restriction endonuclease site (SacI) in the 3' noncoding region of apoC-III mRNA has been correlated with hypertriglyceridemia in humans. In this study, we report the isolation and characterization of cDNA clones containing the entire apoC-III mRNA coding sequence. The nucleotide-derived apoC-III amino acid sequence indicates that the apoC-III primary translational product contains a 20 amino acid N-terminal extension, which conforms with the general properties of known signal peptides, and is highly homologous to the recently reported rat apoC-III signal peptide. The DNA-derived apoC-III amino acid sequence differs from the previously reported apoC-III amino acid sequence at four amino acid residues. More specifically, at positions +32, +33, +37, +39, the DNA sequence predicts Glu, Ser, Gln, Ala, respectively, while the previously reported sequence specifies Ser, Gln, Ala, Gln, respectively. Finally, isolation and characterization of apoC-III cDNA clones, with or without the polymorphic SacI restriction site, indicated that the apoC-III nucleotide sequence corresponding to the Sac+ and Sac- clones differs at three nucleotide sites; however, the amino acid sequence specified by the Sac+ and Sac- alleles is identical.
Highlights
We have recently reported that the human apolipoprotein A-I and apolipoprotein C-I11 genes are physically linked and that the presence of a DNA insertion in the apoA-I gene is correlated with apoA-I-apoC-I11 deficiency in patients with premature atherosclerosis
We have previously shown that the human apoCI11 gene is located approximately 2.6kb to the 3’ direction of the apoA-I gene and that these two genes are convergently transcribed [15]
Chromosomal DNA was prepared from another aliquot of the same liver used to construct the cDNA library and, after digestion with SacI, electrophoresis, blotting, and hybridization with the apoA-I cDNA probe pAI-101 [28], produced 5.7kb, 4.2kb, and 3.2kb hybridization bands
Summary
We have recently reported that the human apolipoprotein A-I (apoA-I) and apolipoprotein C-I11 (apoC-111) genes are physically linked and that the presence of a DNA insertion in the apoA-I gene is correlated with apoA-I-apoC-I11 deficiency in patients with premature atherosclerosis. The presence of a polymorphic restriction endonuclease site (SacI) in the 3’ noncoding region of apoC-I11 mRNA has been correlated with hypertriglyceridemia in humans. We report the isolation and characterization of cDNA clones containing the entire apoC-I11 mRNA coding sequence. The DNA-derived apoC-I11 amino acid sequence differs from the previously reported apoC-I11 amino acid sequence at four amino acid residues. Isolation and characterization of apoC-111 cDNA clones, with or without the polymorphic SacI restriction site, indicated that the apoC-I11 nucleotide sequence corresponding to the Sac+ and Sac- clones differs at three nucleotide sites; the amino acid sequence specified by the Sac’ and Sac- alleles is identical. Isolation and characterization of cDNA clones corresponding to two different human apoC-111 alleles.
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