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Rossmann C, Windpassinger C, Brunner D, Kovacevic A, Schweighofer N, Malli R, Schuligoi R, Prokesch A, Kluve-Beckerman B, Graier WF, Kratky D, Sattler W, Malle E. Characterization of rat serum amyloid A4 (SAA4): a novel member of the SAA superfamily. Biochem Biophys Res Commun 2014; 450:1643-9. [PMID: 25044109 PMCID: PMC4145149 DOI: 10.1016/j.bbrc.2014.07.054] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 07/11/2014] [Indexed: 11/16/2022]
Abstract
The full length rat SAA4 (rSAA4) mRNA was characterized by rapid amplification of cDNA ends. rSAA4 mRNA has 1830 bases including a GA dinucleotide tandem repeat in the 5′UTR. Three consecutive C/EBP promoter elements are crucial for transcription of rSAA4. rSAA4 is abundantly expressed in the liver on mRNA and protein level.
The serum amyloid A (SAA) family of proteins is encoded by multiple genes, which display allelic variation and a high degree of homology in mammals. The SAA1/2 genes code for non-glycosylated acute-phase SAA1/2 proteins, that may increase up to 1000-fold during inflammation. The SAA4 gene, well characterized in humans (hSAA4) and mice (mSaa4) codes for a SAA4 protein that is glycosylated only in humans. We here report on a previously uncharacterized SAA4 gene (rSAA4) and its product in Rattus norvegicus, the only mammalian species known not to express acute-phase SAA. The exon/intron organization of rSAA4 is similar to that reported for hSAA4 and mSaa4. By performing 5′- and 3′RACE, we identified a 1830-bases containing rSAA4 mRNA (including a GA-dinucleotide tandem repeat). Highest rSAA4 mRNA expression was detected in rat liver. In McA-RH7777 rat hepatoma cells, rSAA4 transcription was significantly upregulated in response to LPS and IL-6 while IL-1α/β and TNFα were without effect. Luciferase assays with promoter-truncation constructs identified three proximal C/EBP-elements that mediate expression of rSAA4 in McA-RH7777 cells. In line with sequence prediction a 14-kDa non-glycosylated SAA4 protein is abundantly expressed in rat liver. Fluorescence microscopy revealed predominant localization of rSAA4-GFP-tagged fusion protein in the ER.
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Affiliation(s)
- Christine Rossmann
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | | | - Daniela Brunner
- Institute of Human Genetics, Medical University of Graz, Graz, Austria
| | - Alenka Kovacevic
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Natascha Schweighofer
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Roland Malli
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Rufina Schuligoi
- Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria
| | - Andreas Prokesch
- Institute of Cell Biology, Histology and Embryology, Medical University of Graz, Graz, Austria; Institute of Biochemistry, Graz University of Technology, Graz, Austria
| | - Barbara Kluve-Beckerman
- Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Wolfgang F Graier
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Dagmar Kratky
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Wolfgang Sattler
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Ernst Malle
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria.
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