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Characterization of the murine Nramp1 promoter - Requirements for transactivation by Miz-1

Characterization of the murine Nramp1 promoter - Requirements for transactivation by Miz-1
Characterization of the murine Nramp1 promoter - Requirements for transactivation by Miz-1
Murine Nramp1 encodes a divalent cation transporter that is expressed in late endosomes/lysosomes of macrophages, and the transported cations facilitate intracellular pathogen growth control. The Nramp1 promoter is TATA box-deficient, has two initiator elements, and is repressed by c-Myc, in accordance with the notion that genes that deplete the iron content of the cell cytosol antagonize cell growth. Repression via c-Myc occurs at the initiator elements, whereas a c-Myc-interacting protein (Miz-1) stimulates transcription. Here we demonstrate that a non-canonical E box (CAACTG) inhibits basal promoter activity and activation by Miz-1. A consensus Sp1-binding site or GC box is also necessary for Miz-1-dependent transactivation, but not repression. Repression occurs by c-Myc competing with p300/CBP for binding Miz-1. Our results show that an Sp1 site mutant inhibits coactivation by p300 and that the murine Nramp1 promoter is preferentially expressed within macrophages (relative to a -actin control) compared with non-macrophage cells. The effect of the Sp1 site mutation on promoter function shows cell-type specificity: stimulation in COS-1 and inhibition in RAW264.7 cells. Miz-1-directed RNA interference confirms a stimulatory role for Miz-1 in Nramp1 promoter function. c-Myc, Miz-1, and Sp1 were identified as binding to the Nramp1 core promoter in control cells and following acute stimulation with interferon- and lipopolysaccharide. These results provide a description of sites that modulate the activity of the initiator-binding protein Miz-1 and indicate a stimulatory role for GC box-binding factors in macrophages and a inhibitory role for E box elements in proliferating cells.
0021-9258
36017-36026
Bowen, H.
4ed2a24f-bf81-4d60-b475-567f9ad321bb
Lapham, A.
78311f08-176a-403e-af1f-84cf7523cdc2
Phillips, E.
16ee48e2-0cca-478b-b233-28aca3957406
Yeung, I.
369f79d1-a93d-4a8a-bf2a-5d11ae3c4c5a
Alter-Koltunoff, M.
cab42450-fc91-4cda-940a-2864b95705a8
Levi, B.
0ef210f5-98aa-4d39-b104-4f3e4f8bd746
Perry, V. H.
8f29d36a-8e1f-4082-8700-09483bbaeae4
Mann, D. A.
a1b1006c-7b99-42c8-ac5f-ad24d5e307a1
Barton, C. H.
5dfb4e1a-d559-4b58-9036-31de1e6c9ad8
Bowen, H.
4ed2a24f-bf81-4d60-b475-567f9ad321bb
Lapham, A.
78311f08-176a-403e-af1f-84cf7523cdc2
Phillips, E.
16ee48e2-0cca-478b-b233-28aca3957406
Yeung, I.
369f79d1-a93d-4a8a-bf2a-5d11ae3c4c5a
Alter-Koltunoff, M.
cab42450-fc91-4cda-940a-2864b95705a8
Levi, B.
0ef210f5-98aa-4d39-b104-4f3e4f8bd746
Perry, V. H.
8f29d36a-8e1f-4082-8700-09483bbaeae4
Mann, D. A.
a1b1006c-7b99-42c8-ac5f-ad24d5e307a1
Barton, C. H.
5dfb4e1a-d559-4b58-9036-31de1e6c9ad8

Bowen, H., Lapham, A., Phillips, E., Yeung, I., Alter-Koltunoff, M., Levi, B., Perry, V. H., Mann, D. A. and Barton, C. H. (2003) Characterization of the murine Nramp1 promoter - Requirements for transactivation by Miz-1. The Journal of Biological Chemistry, 278 (38), 36017-36026. (doi:10.1074/jbc.M304301200).

Record type: Article

Abstract

Murine Nramp1 encodes a divalent cation transporter that is expressed in late endosomes/lysosomes of macrophages, and the transported cations facilitate intracellular pathogen growth control. The Nramp1 promoter is TATA box-deficient, has two initiator elements, and is repressed by c-Myc, in accordance with the notion that genes that deplete the iron content of the cell cytosol antagonize cell growth. Repression via c-Myc occurs at the initiator elements, whereas a c-Myc-interacting protein (Miz-1) stimulates transcription. Here we demonstrate that a non-canonical E box (CAACTG) inhibits basal promoter activity and activation by Miz-1. A consensus Sp1-binding site or GC box is also necessary for Miz-1-dependent transactivation, but not repression. Repression occurs by c-Myc competing with p300/CBP for binding Miz-1. Our results show that an Sp1 site mutant inhibits coactivation by p300 and that the murine Nramp1 promoter is preferentially expressed within macrophages (relative to a -actin control) compared with non-macrophage cells. The effect of the Sp1 site mutation on promoter function shows cell-type specificity: stimulation in COS-1 and inhibition in RAW264.7 cells. Miz-1-directed RNA interference confirms a stimulatory role for Miz-1 in Nramp1 promoter function. c-Myc, Miz-1, and Sp1 were identified as binding to the Nramp1 core promoter in control cells and following acute stimulation with interferon- and lipopolysaccharide. These results provide a description of sites that modulate the activity of the initiator-binding protein Miz-1 and indicate a stimulatory role for GC box-binding factors in macrophages and a inhibitory role for E box elements in proliferating cells.

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Published date: 2003

Identifiers

Local EPrints ID: 24073
URI: https://eprints.soton.ac.uk/id/eprint/24073
ISSN: 0021-9258
PURE UUID: 7f094b8e-bb7c-4052-88da-1e28e8a7d546

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Date deposited: 21 Mar 2006
Last modified: 15 Jul 2019 19:19

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