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Regulated expression of alternate transcripts from the mouse oncostatin M gene: implications for interleukin-6 family
1Department of Biochemistry, University of Adelaide, Adelaide, SA, 5005, Australia.
Abstract:
Oncostatin M (OSM) is a member of the IL-6 family of polyfunctional cytokines. The characterized murine OSM transcript consists of three exons and encodes a secreted protein. Investigations of mOSM expression using the ribonuclease protection assay demonstrated novel sites of expression in undifferentiated but not differentiated pluripotent cells, and revealed the existence of alternatively spliced mOSM transcripts. cDNAs representing a novel mOSM transcript (mOSM 13) containing exon 1 spliced directly to exon 3 were isolated from bone marrow using Rapid Amplification of cDNA Ends (RACE) PCR and RT-PCR approaches. Expression of the mOSM 13 transcript was regulated in a tissue-specific manner and independently of mOSM transcript production, suggesting that its production is biologically significant. Splicing of exon 1 directly to exon 3 disrupts the OSM open reading frame of mOSM 13. Initiation of translation at sites within exon 3 of mOSM 13 would yield N-terminally truncated OSM proteins that are localized within the cell. The omission of exon 2 by alternate splicing and the production of intracellular proteins with alternate biological activities are conserved among several IL-6 family cytokines and are one manifestation of a more general phenomenon; the production of alternate cytokine transcripts encoding intracellular and extracellular proteins.
Insights
Researchers discovered a novel Oncostatin M (OSM) transcript (mOSM 13) in mice, produced via alternative splicing. This transcript encodes intracellular OSM proteins, suggesting diverse biological functions beyond secreted cytokines.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- Oncostatin M (OSM) is a polyfunctional cytokine belonging to the IL-6 family.
- The standard murine OSM transcript comprises three exons, encoding a secreted protein.
Purpose of the Study:
- To investigate novel sites of murine OSM expression.
- To identify and characterize alternatively spliced OSM transcripts.
- To explore the biological significance of alternative splicing in OSM production.
Main Methods:
- Ribonuclease protection assay for expression analysis.
- Rapid Amplification of cDNA Ends (RACE) PCR for transcript isolation.
- RT-PCR to confirm transcript presence and structure.
Main Results:
- Novel murine OSM expression identified in undifferentiated pluripotent cells.
- A new transcript, mOSM 13, was isolated, featuring exon 1 spliced directly to exon 3.
- mOSM 13 expression is tissue-specific and independent of standard OSM transcript production.
- Alternative splicing disrupts the standard OSM open reading frame, leading to intracellular protein variants.
Conclusions:
- Alternative splicing of the OSM gene produces distinct transcripts, including mOSM 13.
- These alternatively spliced transcripts encode intracellular OSM proteins, suggesting novel cellular functions.
- The production of intracellular cytokine variants via alternative splicing is a conserved mechanism within the IL-6 family.