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A cDNA clone expressed in natural killer and T cells that likely encodes a secreted protein
1Department of Laboratory Medicine, University of Minnesota, Minneapolis 55455.
Abstract:
We have isolated a series of cross-hybridizing cDNA clones, as a group designated as NKG5, from a human natural killer (NK) cell clone cDNA library. These clones show a high degree of homology with a previously described gene, 519, which was thought to be T cell specific. A comparison of the full-length cDNA sequence of NKG5 and the published sequence of 519 shows that NKG5 lacks a 242-base segment that is found in 519 and that this deletion leads to the use of a different putative translational start codon. Unlike 519, the predicted NKG5 polypeptide has an NH2-terminal sequence that is strongly hydrophobic, characteristic of a signal peptide, and lacks any additional hydrophobic regions in the remainder of the peptide, suggesting that NKG5 encodes a secreted protein. Both NKG5 and 519 are expressed in NK and T cells but not in a variety of other hematopoietic cell lines. NKG5 is an abundant transcript and its level of expression is about 40 times that of 519 in NK and T cells. Southern blot and DNA sequence analyses suggest that NKG5 and 519 mRNAs are transcripts from a single gene that has allelic polymorphism.
Insights
Researchers identified NKG5, a novel gene highly expressed in natural killer (NK) and T cells. This gene, similar to 519, encodes a secreted protein and may arise from allelic polymorphism.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- Natural Killer (NK) cells and T cells are crucial components of the adaptive and innate immune systems.
- Previous research identified a gene, 519, with presumed specificity for T cells.
- Understanding novel gene expression in immune cells is vital for immunology and disease research.
Purpose of the Study:
- To isolate and characterize novel cDNA clones from human NK cell libraries.
- To compare the novel NKG5 gene with the previously identified 519 gene.
- To elucidate the structure, expression, and potential function of the NKG5 gene.
Main Methods:
- Isolation of cross-hybridizing cDNA clones from a human NK cell library.
- DNA sequence analysis and comparison of NKG5 and 519 full-length cDNA.
- Southern blot analysis to investigate gene structure and polymorphism.
- Analysis of polypeptide structure, including signal peptide prediction.
Main Results:
- A novel group of cDNA clones, designated NKG5, was isolated and found to be highly homologous to the 519 gene.
- NKG5 differs from 519 by a 242-base deletion, resulting in a different translational start codon and a predicted secreted protein.
- Both NKG5 and 519 are expressed in NK and T cells, but not other hematopoietic cell lines.
- NKG5 is an abundant transcript in NK and T cells, approximately 40 times higher than 519.
- Evidence suggests NKG5 and 519 mRNAs are transcripts from a single gene with allelic polymorphism.
Conclusions:
- NKG5 represents a distinct gene product compared to 519, with characteristics of a secreted protein.
- The expression pattern of NKG5 in NK and T cells suggests a role in immune cell function.
- NKG5 and 519 likely originate from a single polymorphic gene, indicating allelic variation within immune cells.