Structural organization, sequence, and expression of the chicken NRAMP1 gene encoding the natural resistance-associated macrophage protein 1.

One of the most common causes of food poisoning in humans is salmonellosis, which is frequently caused by ingestion with Salmonella-contaminated poultry products. Several lines of evidence suggest that genetic factors control resistance and susceptibility of chickens to infection with Salmonellae. In the mouse, innate resistance to infection with intracellular pathogens such as Salmonella typhimurium, several species of Mycobacteria, and Leishmania donovani is controlled by the mouse chromosome 1 Nramp1Bcg gene. To investigate the role of NRAMP1 in the differential resistance and susceptibility of chickens to infections with S. typhimurium, we have cloned and characterized cDNA clones corresponding to the chicken NRAMP1 gene. Nucleotide and predicted amino acid sequence analyses indicate that the chicken NRAMP1 polypeptide encodes a 555-amino-acid residue membrane protein with 12 putative transmembrane domains, two N-linked glycosylation sites, and an evolutionary conserved consensus transport motif. The peptide sequence identity among chicken, mouse, and human NRAMP1 is 68%. The chicken NRAMP1 gene contains 15 exons and spans 5 kb of genomic DNA. One major and two minor transcription initiation sites were detected using primer extension. Nucleotide sequencing of the promoter region revealed the presence of a classical TATAA element and consensus sequences for binding the myeloid specific PU.1 factor and several lipopolysaccharide (LPS) (NF-IL6 and NF-kappa B) and interferon-gamma (IFN-gamma)-inducible response elements. Similar regulatory elements are found in the promoters of mouse and human NRAMP1. Northern blot analyses revealed NRAMP1 expression in reticuloendothelial organs (spleen and liver), lung, and thymus. As demonstrated in mice and humans, the macrophage is also a major site of NRAMP1 mRNA expression in chickens. However, the high levels of expression detected in chicken thymus contrast with the absence of expression of the mammalian Nramp1 gene in this tissue.

Hu J ，Bumstead N ，Skamene E ，Gros P ，Malo D ... -  《DNA AND CELL BIOLOGY》

Genomic structure, promoter sequence, and induction of expression of the mouse Nramp1 gene in macrophages.

A candidate gene for the mouse chromosome 1 host resistance locus Bcg/Ity/Lsh was recently cloned and designated Nramp (natural resistance-associated macrophage protein). Nramp is part of a small family of at least two genes, Nramp1 and Nramp2. Primer extension and cDNA cloning were used to isolate the complete 5' end of the Nramp1 mRNA. Analysis of genomic cosmid and bacteriophage clones overlapping the complete Nramp1 gene revealed that the gene was composed of 15 exons and spanned 11.5 kb of genomic DNA. Positioning of introns on the coding portion of the mRNA revealed a modular relationship between coding exons and predicted structural domains of the protein, with 8 of the 12 transmembrane (TM) domains encoded by individual exons. Northern blotting analysis indicated that Nramp1 expression was restricted to J774A.1 and RAW 264.7 macrophage lines and was dramatically increased by treatment with interferon-gamma (IFN-gamma) and lipopolysaccharide (LPS). Primer extension and S1 nuclease mapping experiments were used to locate the transcription initiation site of Nramp1 and revealed the presence of one major and several minor initiation sites. Nucleotide sequencing of the corresponding region failed to detect classical TATA and CAAT elements, but identified two putative initiator sequences located near the major initiation site. Consensus sequences for binding of the macrophage and B-cell-specific transcription factor PU.1, as well as several LPS (NF-IL6) and IFN-gamma response elements, were also identified.

Govoni G ，Vidal S ，Cellier M ，Lepage P ，Malo D ，Gros P ... -  《GENOMICS》

Resistance to salmonellosis in the chicken is linked to NRAMP1 and TNC.

Hu J ，Bumstead N ，Barrow P ，Sebastiani G ，Olien L ，Morgan K ，Malo D ... -  《GENOME RESEARCH》

Complete nucleotide sequence and genomic structure of the human NRAMP1 gene region on chromosome region 2q35.

Marquet S ，Lepage P ，Hudson TJ ，Musser JM ，Schurr E ... -  《MAMMALIAN GENOME》

cDNA cloning, structural organization, and expression of the sheep NRAMP1 gene.

Bussmann V ，Lantier I ，Pitel F ，Patri S ，Nau F ，Gros P ，Elsen JM ，Lantier F ... -  《MAMMALIAN GENOME》