Related Experiment Videos
Genomic organization and sequence of the human NRAMP gene: identification and mapping of a promoter region
J M Blackwell1, C H Barton, J K White
1University of Cambridge Clinical School, Department of Medicine, Addenbrooke's Hospital, United Kingdom.
Background:
Murine Nramp is a candidate for the macrophage resistance gene Ity/Lsh/Bcg. Sequence analysis of human NRAMP was undertaken to determine its role in man.
Materials And Methods:
A yeast artificial chromosome carrying NRAMP was subcloned and positive clones sequenced. The transcriptional start site was mapped using 5' RACE PCR. Polymorphic variants were amplified by PCR. Linkage analysis was used to map NRAMP.
Results:
NRAMP spans 12kb and has 15 exons encoding a 550 amino acid protein showing 85% identity (92% similarity) with Nramp. Two conserved PKC sites occur in exon 2 encoding the Pro/Ser rich SH3 binding domain, and in exon 3. Striking sequence similarities (57 and 53%) were observed with yeast mitochondrial proteins, SMF1 and SMF2, especially within putative functional domains: exon 6 encoding the second transmembrane spanning domain, site of the murine susceptibility mutation; and exon 11 encoding a conserved transport motif. No mutations comparable to the murine susceptibility mutation were found. The transcriptional initiation site mapped 148 bp 5' of the translational initiation codon. 440bp of 5' flanking sequence contained putative promoter region elements: 6 interferon-gamma response elements, 3 W-elements, 3 NF kappa B binding sites and 1 AP-1 site. Nine purine-rich GGAA core motifs for the myeloid-specific PU.1 transcription factor were identified, two combining with imperfect AP1-like sites to create PEA3 motifs. TATA, GC and CCAAT boxes were absent. A possible enhancer element containing the Z-DNA forming dinucleotide repeat t(gt),ac(gt),ac(gt),g was polymorphic (4 alleles; n = 4,9,10,11), and was used to map NRAMP to 2q35.
Conclusions:
This analysis provides important resources to study the role of NRAMP in human disease.
Insights
Human NRAMP, a homolog of the murine macrophage resistance gene, was analyzed. Its gene structure, promoter elements, and chromosomal location were determined, providing resources for studying its role in human disease.
Area of Science:
- Genetics and Molecular Biology
- Human genetics
- Gene structure and function
Background:
- Murine Nramp (natural resistance-associated macrophage protein) is a candidate gene for macrophage resistance (Ity/Lsh/Bcg).
- Human NRAMP gene sequence analysis was performed to elucidate its role in human health and disease.
Observation:
- Human NRAMP gene spans 12kb with 15 exons, encoding a 550 amino acid protein with 85% identity to murine Nramp.
- Conserved protein kinase C (PKC) sites were identified in exons 2 and 3.
- Significant sequence similarities were found with yeast mitochondrial proteins SMF1 and SMF2, particularly in functional domains.
- The transcriptional start site was mapped 148 bp upstream of the translational start codon.
- The 5' flanking region contains putative promoter elements including interferon-gamma, NF-kappa B, and AP-1 binding sites, as well as PU.1 motifs.
- A polymorphic enhancer element with a Z-DNA forming repeat was identified and used for gene mapping.
Findings:
- Human NRAMP shares high sequence identity and conserved functional domains with its murine homolog and yeast mitochondrial transporters.
- The human NRAMP gene possesses a complex promoter region with multiple regulatory elements.
- No mutations analogous to the murine susceptibility mutation were identified in the analyzed human NRAMP sequence.
- The human NRAMP gene was mapped to chromosome 2q35 using a polymorphic enhancer element.
Implications:
- This detailed characterization of the human NRAMP gene provides essential resources for investigating its involvement in human diseases.
- Understanding NRAMP's genetic and regulatory features can facilitate research into macrophage function and immune responses.
- The identification of conserved domains and regulatory elements opens avenues for comparative genomics and functional studies.