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Abstract
Serum amyloid A (SAA) proteins were isolated and named over 50 years ago. They are small (104 amino acids) and have a striking relationship to the acute phase response with serum levels rising as much as 1000-fold in 24 hours. SAA proteins are encoded in a family of closely-related genes and have been remarkably conserved throughout vertebrate evolution. Amino-terminal fragments of SAA can form highly organized, insoluble fibrils that accumulate in “secondary” amyloid disease. Despite their evolutionary preservation and dynamic synthesis pattern SAA proteins have lacked well-defined physiologic roles. However, considering an array of many, often unrelated, reports now permits a more coordinated perspective. Protein studies have elucidated basic SAA structure and fibril formation. Appreciating SAA’s lipophilicity helps relate it to lipid transport and metabolism as well as atherosclerosis. SAA’s function as a cytokine-like protein has become recognized in cell-cell communication as well as feedback in inflammatory, immunologic, neoplastic and protective pathways. SAA likely has a critical role in control and possibly propagation of the primordial acute phase response. Appreciating the many cellular and molecular interactions for SAA suggests possibilities for improved understanding of pathophysiology as well as treatment and disease prevention.
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Affiliation(s)
- George H Sack
- Departments of Biological Chemistry and Medicine, The Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Physiology 615, Baltimore, MD, 21205, USA.
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Álvaro-Blanco J, Urso K, Chiodo Y, Martín-Cortázar C, Kourani O, Arco PGD, Rodríguez-Martínez M, Calonge E, Alcamí J, Redondo JM, Iglesias T, Campanero MR. MAZ induces MYB expression during the exit from quiescence via the E2F site in the MYB promoter. Nucleic Acids Res 2017; 45:9960-9975. [PMID: 28973440 PMCID: PMC5622404 DOI: 10.1093/nar/gkx641] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Accepted: 07/13/2017] [Indexed: 12/27/2022] Open
Abstract
Most E2F-binding sites repress transcription through the recruitment of Retinoblastoma (RB) family members until the end of the G1 cell-cycle phase. Although the MYB promoter contains an E2F-binding site, its transcription is activated shortly after the exit from quiescence, before RB family members inactivation, by unknown mechanisms. We had previously uncovered a nuclear factor distinct from E2F, Myb-sp, whose DNA-binding site overlapped the E2F element and had hypothesized that this factor might overcome the transcriptional repression of MYB by E2F-RB family members. We have purified Myb-sp and discovered that Myc-associated zinc finger proteins (MAZ) are major components. We show that various MAZ isoforms are present in Myb-sp and activate transcription via the MYB-E2F element. Moreover, while forced RB or p130 expression repressed the activity of a luciferase reporter driven by the MYB-E2F element, co-expression of MAZ proteins not only reverted repression, but also activated transcription. Finally, we show that MAZ binds the MYB promoter in vivo, that its binding site is critical for MYB transactivation, and that MAZ knockdown inhibits MYB expression during the exit from quiescence. Together, these data indicate that MAZ is essential to bypass MYB promoter repression by RB family members and to induce MYB expression.
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Affiliation(s)
- Josué Álvaro-Blanco
- Department of Cancer Biology, Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, Madrid 28029, Spain
| | - Katia Urso
- Gene regulation in cardiovascular remodeling and inflammation group, Centro Nacional de Investigaciones Cardiovasculares, Madrid 28029, Spain
| | - Yuri Chiodo
- Department of Cancer Biology, Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, Madrid 28029, Spain
| | - Carla Martín-Cortázar
- Department of Cancer Biology, Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, Madrid 28029, Spain
| | - Omar Kourani
- Department of Cancer Biology, Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, Madrid 28029, Spain
| | - Pablo Gómez-Del Arco
- Gene regulation in cardiovascular remodeling and inflammation group, Centro Nacional de Investigaciones Cardiovasculares, Madrid 28029, Spain.,Department of Molecular Biology, Universidad Autónoma de Madrid, Centro de Biología Molecular, Cantoblanco, Madrid 28049, Spain.,CIBERCV, Spain
| | - María Rodríguez-Martínez
- Department of Cancer Biology, Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, Madrid 28029, Spain
| | - Esther Calonge
- Unidad de Inmunopatología del SIDA, Centro Nacional de Microbiología, Majadahonda 28220, Spain
| | - José Alcamí
- Unidad de Inmunopatología del SIDA, Centro Nacional de Microbiología, Majadahonda 28220, Spain
| | - Juan Miguel Redondo
- Gene regulation in cardiovascular remodeling and inflammation group, Centro Nacional de Investigaciones Cardiovasculares, Madrid 28029, Spain.,CIBERCV, Spain
| | - Teresa Iglesias
- Department of Endocrine and Nervous Systems Pathophysiology, Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, Madrid 28029, Spain.,CIBERNED, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, Spain
| | - Miguel R Campanero
- Department of Cancer Biology, Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, Madrid 28029, Spain.,CIBERCV, Spain
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Filep JG, El Kebir D. Serum amyloid A as a marker and mediator of acute coronary syndromes. Future Cardiol 2010; 4:495-504. [PMID: 19804343 DOI: 10.2217/14796678.4.5.495] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Inflammation promotes acute coronary syndromes and ensuing clinical complications. An emerging downstream marker of inflammation is serum amyloid A (SAA). Elevated plasma SAA levels predict increased cardiovascular risk and portend worse prognosis in patients with acute coronary artery disease (CAD). The pathophysiological role of SAA remains enigmatic. SAA plays a role in host defense, but it might also be atherogenic. SAA affects cholesterol transport, contributes to endothelial dysfunction, promotes thrombosis, evokes recruitment of inflammatory cells, activates neutrophils and suppresses neutrophil apoptosis, key events underlying acute coronary syndromes. These results provide a potential link between SAA and CAD and suggest that reducing SAA levels and/or opposing the actions of SAA may have beneficial effects in patients with acute CAD.
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Affiliation(s)
- János G Filep
- University of Montréal, Research Center, Maisonneuve-Rosemont Hospital & Department of Pathology & Cell Biology, Montréal, QC H1T2M4, Canada.
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Ray A, Dhar S, Shakya A, Ray P, Okada Y, Ray BK. SAF-3, a novel splice variant of the SAF-1/MAZ/Pur-1 family, is expressed during inflammation. FEBS J 2009; 276:4276-86. [PMID: 19583771 DOI: 10.1111/j.1742-4658.2009.07136.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Cys2His2-type zinc finger transcription factor serum amyloid A activating factor 1 [SAF-1, also known as MAZ (myc-associated zinc finger protein) or Pur-1 (purine binding factor-1)] plays an important role in regulation of a variety of inflammation-responsive genes. An SAF-2 splice variant acting as a negative regulator of SAF-1 was identified previously, and the present study reports the identification of a novel SAF-3 splice variant that is expressed during inflammation. SAF-3 mRNA, isolated from a cDNA library produced from IL-1beta-induced cells, originates from a previously unknown first coding exon, and thereby contains a unique N-terminal domain but shares the same six zinc finger DNA-binding domains as present in SAF-1. In addition, a negatively functioning domain present at the N-terminus of SAF-1 and SAF-2 is spliced out in SAF-3. The expression of SAF-3 is very low in normal tissues and in cells grown under normal conditions. However, RT-PCR analysis of mRNAs from cytokine and growth factor-induced cells as well of mRNAs isolated from several diseased tissues revealed abundant expression of SAF-3. The transactivation potential of SAF-3 is much greater than that of the predominantly expressed splice variant SAF-1. These findings show that transcriptional regulation of downstream inflammation-responsive genes by SAF/MAZ/Pur-1 is likely to be more complex than previously assumed. In addition, we show that SAF-3 expression initiates from an upstream novel promoter. This is the first report of the existence of multiple promoters regulating expression of the SAF/MAZ/Pur-1 family of proteins.
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Affiliation(s)
- Alpana Ray
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA.
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Kovacevic A, Hammer A, Stadelmeyer E, Windischhofer W, Sundl M, Ray A, Schweighofer N, Friedl G, Windhager R, Sattler W, Malle E. Expression of serum amyloid A transcripts in human bone tissues, differentiated osteoblast-like stem cells and human osteosarcoma cell lines. J Cell Biochem 2008; 103:994-1004. [PMID: 17849429 PMCID: PMC4861207 DOI: 10.1002/jcb.21472] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Although the liver is the primary site of cytokine-mediated expression of acute-phase serum amyloid A (SAA) protein, extrahepatic production has also been reported. Besides its role in amyloidosis and lipid homeostasis during the acute-phase, SAA has recently been assumed to contribute to bone and cartilage destruction. However, expression of SAA in human osteogenic tissue has not been studied. Therefore, we first show that SAA1 (coding for the major SAA isoform) but not SAA2 transcripts are expressed in human trabecular and cortical bone fractions and bone marrow. Next, we show expression of (i) IL-1, IL-6, and TNF receptor transcripts; (ii) the human homolog of SAA-activating factor-1 (SAF-1, a transcription factor involved in cytokine-mediated induction of SAA genes); and (iii) SAA1/2 transcripts in non-differentiated and, to a higher extent, in osteoblast-like differentiated human mesenchymal stem cells. Third, we provide evidence that human osteoblast-like cells of tumor origin (MG-63 and SAOS-2) express SAF-1 under basal conditions. SAA1/2 transcripts are expressed under basal conditions (SAOS-2) and cytokine-mediated conditions (MG-63 and SAOS-2). RT-PCR, Western blot analysis, and immunofluorescence technique confirmed cytokine-mediated expression of SAA on RNA and protein level in osteosarcoma cell lines while SAA4, a protein of unknown function, is constitutively expressed in all osteogenic tissues investigated.
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Affiliation(s)
- Alenka Kovacevic
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Center of Molecular Medicine, Graz, Austria
| | - Astrid Hammer
- Institute of Cell Biology, Histology and Embryology, Center of Molecular Medicine, Medical University of Graz, Center of Molecular Medicine, Graz, Austria
| | - Elke Stadelmeyer
- Department of Orthopaedics, Graz University Hospital, Medical University of Graz, Graz, Austria
| | - Werner Windischhofer
- Department of Pediatrics, Research Unit of Osteological Research and Analytical Mass Spectrometry, Medical University of Graz, Graz, Austria
| | - Monika Sundl
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Center of Molecular Medicine, Graz, Austria
| | - Alpana Ray
- Department of Veterinary Pathobiology, University of Missouri-Columbia, Columbia, MO 65211
| | - Natascha Schweighofer
- Division of Endocrinology and Nuclear Medicine, Department of Internal Medicine, Medical University of Graz, Graz, Austria
| | - Gerald Friedl
- Department of Orthopaedics, Graz University Hospital, Medical University of Graz, Graz, Austria
| | - Reinhard Windhager
- Department of Orthopaedics, Graz University Hospital, Medical University of Graz, Graz, Austria
| | - Wolfgang Sattler
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Center of Molecular Medicine, Graz, Austria
| | - Ernst Malle
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Center of Molecular Medicine, Graz, Austria
- Correspondence to: Ernst Malle, Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, A-8010 Graz, Austria.
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Ray BK, Shakya A, Ray A. Vascular endothelial growth factor expression in arthritic joint is regulated by SAF-1 transcription factor. THE JOURNAL OF IMMUNOLOGY 2007; 178:1774-82. [PMID: 17237427 DOI: 10.4049/jimmunol.178.3.1774] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Vascular endothelial growth factor (VEGF) plays an important role in the pathogenesis of arthritis by promoting angiogenesis in the synovial joint and infiltration of inflammatory cells in the synovial joint. Although ample information has been obtained on the mechanism of VEGF regulation during cancer and hypoxic condition, less is known about the control of VEGF expression during arthritis. From the studies on the experimentally induced arthritis in a transgenic mouse model that overexpresses a transcription factor, serum amyloid A activating factor-1 (SAF-1), leading to markedly higher levels of angiogenesis, synovial inflammation, and inflammatory cell infiltration, we have identified a novel mechanism of VEGF regulation. We present molecular evidence that VEGF expression is increased in SAF-1-transgenic mice and that SAF-1 induces VEGF transcription by directly binding to its promoter. Deletion of SAF-1 binding elements from the VEGF promoter as well as knockdown of endogenous SAF-1 markedly inhibited IL-1beta- and TGF-beta-mediated induction of VEGF expression in chondrocyte cells. By chromatin immunoprecipitation assay, in vivo, markedly higher levels of SAF-1 interaction with the VEGF promoter was detected in the cartilage tissues of arthritic mice as well as human osteoarthritic patients. Together, these results provide a new insight into the molecular mechanism of VEGF expression.
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Affiliation(s)
- Bimal K Ray
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA
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