Nonexpression of the Human Serum Amyloid A Three (SAA3) Gene

Barbara Kluve-Beckerman, Mitchell L. Drumm, Merrill D. Benson

Research output: Contribution to journalArticle

90 Scopus citations

Abstract

Serum amyloid A (SAA) is a major acute-phase plasma protein synthesized by the liver. In addition to the two major plasma isoforms described in humans (SAA1 and SAA2), a third form (SAA3) has been demonstrated in several other species and is distinguished by predominant extrahepatic expression. Two clones, Ch11g5-1-1 and HDg1-1, containing the human SAA3 gene are described in this report. The human SAA3 gene is comparable in organization to the SAA1 and SAA2 genes and shares with them 87% nucleotide identity in the region spanning exon 3 through exon 4. Sequences 5′ to exon 3, however, are strikingly different from those in the SAA1 and SAA2 genes. For instance, the sequence deduced for amino acids 1–12 (exon 2) has only 25% identity with human SAA1 and SAA2; it most closely resembles that of rabbit SAA3 isolated from synovial fibroblast cultures (75% identity). Although rabbit SAA3 induces collagenase production in an autocrine fashion the human SAA3 gene is not expressed. This is shown by: (i) a single base insertion in the sequence corresponding to codon 31, (ii) the inability of a 918-bp fragment immediately upstream from SAA3 exon sequences to direct transcription of a chloramphenicol acetyltransferase reporter gene, and (iii) the absence of detectable human SAA3 in mRNA.

Original languageEnglish (US)
Pages (from-to)651-661
Number of pages11
JournalDNA and Cell Biology
Volume10
Issue number9
DOIs
StatePublished - Nov 1991

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cell Biology

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