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Identification of an alternatively spliced transcript of human interleukin-4 lacking the sequence encoded by exon 2
R V Sorg1, J Enczmann, U R Sorg
1Immunology Laboratory, Heinrich Heine University of Düsseldorf, Germany.
Abstract:
The expression of interleukin-4 (IL-4) mRNA of human peripheral blood mononuclear cells stimulated with phytohemagglutinin (PHA) for 15 hours was analyzed by reverse transcription and subsequent polymerase chain reaction (RT/PCR). These analyses revealed an additional smaller fragment that hybridizes with an IL-4 cDNA probe and an oligonucleotide that is specific for a fragment lacking the sequence encoded by exon 2. Sequencing of this fragment demonstrates that it is generated from an alternatively spliced transcript of the IL-4 gene with the sequence encoded by exon 2 being skipped. Skipping of exon 2 does not result in a frame shift but would delete part of the mature protein (48 bp coding for amino acid residues 22 to 37), including Cys24 but not a region directly involved in receptor binding. Differential splicing of other exons or exon combinations has not been observed. The data suggest that the alternatively spliced transcript is not generated by a splicing or PCR error and is not detectable solely because of the high sensitivity of RT/PCR, but in contrast, argue for a physiological role of the transcript and its potentially encoded protein.
Insights
Researchers discovered an alternatively spliced interleukin-4 (IL-4) mRNA transcript in human cells. This finding suggests a potential new role for IL-4 in biological processes.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- Interleukin-4 (IL-4) is a key cytokine involved in immune responses.
- Understanding IL-4 gene expression and its regulation is crucial for immunology research.
Purpose of the Study:
- To investigate the expression of IL-4 mRNA in human peripheral blood mononuclear cells (PBMCs).
- To identify and characterize any novel IL-4 transcripts.
- To determine the potential physiological significance of observed IL-4 variants.
Main Methods:
- Human PBMCs were stimulated with phytohemagglutinin (PHA).
- RNA was extracted and analyzed using reverse transcription and polymerase chain reaction (RT/PCR).
- IL-4 specific cDNA probes and oligonucleotides were used for hybridization and sequencing.
Main Results:
- An alternatively spliced IL-4 mRNA transcript was detected, lacking exon 2.
- Sequencing confirmed the absence of exon 2, resulting in a shorter protein fragment.
- This alternative splicing did not cause a frameshift and preserved the receptor-binding region.
Conclusions:
- The alternatively spliced IL-4 transcript is likely a genuine biological product, not an artifact.
- The data suggest a potential physiological role for this alternatively spliced IL-4 variant.
- Further research is warranted to elucidate the function of the alternatively spliced IL-4 protein.