Abstract
Apolipoprotein[a] (apo[a]), a unique component of atherogenic lipoprotein[a], is highly polymorphic in human and nonhuman primates. Null alleles, producing no detectable circulating Lp[a] or apo[a] isoforms, are found at high frequencies. The molecular basis of null alleles is not yet known. In baboons, approximately two-thirds of null alleles do not produce detectable hepatic transcripts (transcript negative nulls), and one-third of null alleles produce normal amounts of apo[a] transcripts (transcript positive nulls). We have cloned apo[a] cDNA from a baboon carrying a transcript positive null allele defective in secretion from primary hepatocytes. Compared with wild-type cDNA, the null allele contained an in- frame 47 amino acid deletion in the protease domain corresponding to one exon of the apo[a] gene. The null allele contains an A→T substitution in the third nucleotide position of the intron downstream of the deleted exon which alters the donor splice site consensus sequence. Thus, this null is likely due to a mutation that prevents normal mRNA splicing, yielding a shortened protein that may be defective in intramolecular interactions required for normal processing and secretion of apo[a]. This is the first report of a molecular basis for apo[a] null alleles.
Original language | English (US) |
---|---|
Pages (from-to) | 1319-1326 |
Number of pages | 8 |
Journal | Journal of lipid research |
Volume | 39 |
Issue number | 7 |
State | Published - Jul 1998 |
Keywords
- Lipid metabolism
- Plasminogen
- Protein secretion
- Transcript processing
ASJC Scopus subject areas
- Biochemistry
- Endocrinology
- Cell Biology