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A 1.8 kb alternative transcript from the human epidermal growth factor receptor gene encodes a truncated form of the
1Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905, USA.
Abstract:
The epidermal growth factor receptor (EGFR) is encoded by the c-erbB1 proto-oncogene and plays an important role in the control of cell growth and differentiation. To study the potential growth regulatory role of soluble EGF receptors, we have isolated cDNA clones encoding a truncated, secreted form of the human EGFR. The 5' sequence of this cDNA is identical to the EGFR transcript encoding the full-length receptor through exon 10. The unique 3' sequence encodes two additional amino acid residues before encountering an in-frame stop codon, a poly(A) addition site and a poly(A)+ tail. Sequence comparison with genomic DNA sequences demonstrates that this alternative transcript arises by read-through of a splice donor site. As a result, this transcript encodes a portion of the extracellular ligand-binding domain, but lacks the transmembrane domain and the intracellular tyrosine kinase catalytic domain present in the EGFR. Conditioned medium from transfected fibroblast cells contains a 60 kDa protein that is specifically immunoprecipitated by an EGFR monoclonal antibody. These findings demonstrate that alternative processing of the human EGFR transcript produces a secreted product composed of only the extracellular ligand-binding domain.
Insights
Researchers discovered a secreted form of the epidermal growth factor receptor (EGFR) due to alternative gene processing. This soluble EGFR lacks key domains, suggesting a novel role in cell growth regulation.
Area of Science:
- Molecular Biology
- Cell Biology
- Oncology
Background:
- The epidermal growth factor receptor (EGFR), encoded by the c-erbB1 proto-oncogene, is crucial for regulating cell growth and differentiation.
- Soluble forms of growth factor receptors are implicated in modulating cellular responses.
Purpose of the Study:
- To investigate the potential growth regulatory role of soluble EGF receptors.
- To isolate and characterize cDNA clones encoding a truncated, secreted form of the human EGFR.
Main Methods:
- Isolation of cDNA clones encoding a truncated human EGFR.
- Sequence comparison of cDNA with genomic DNA.
- Transfection of fibroblast cells and analysis of secreted proteins via immunoprecipitation.
Main Results:
- Identified a novel transcript variant of human EGFR arising from alternative splicing (read-through of a splice donor site).
- This transcript encodes a secreted protein comprising the extracellular ligand-binding domain but lacking transmembrane and intracellular tyrosine kinase domains.
- A 60 kDa secreted protein, immunoprecipitated by an EGFR antibody, was detected in conditioned medium from transfected cells.
Conclusions:
- Alternative processing of the human EGFR transcript generates a secreted protein containing only the extracellular ligand-binding domain.
- This finding provides evidence for a soluble EGFR variant with potential implications in cell growth and differentiation control.