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Cloning and sequencing of the rat preproepidermal growth factor cDNA: comparison with mouse and human sequences
S J Saggi1, R Safirstein, P M Price
1Department of Medicine, Mount Sinai School of Medicine, New York, NY 10029.
Abstract:
We have cloned and sequenced the cDNA corresponding to the rat preproepidermal growth factor (ppEGF) mRNA. The cDNA contained 4,801 nucleotides, similar to that reported for the mouse (4,749 nucleotides) and the human mRNAs (4,871 nucleotides). The predicted protein sequence would contain 1,133 amino acids, smaller than that reported for the mouse (1,217 amino acids) and the human sequences (1,207 amino acids). The results of the sequencing of several cDNA clones suggested the existence of more than one structural gene for ppEGF. In addition, there was an occurrence of alternative splicing events, resulting in deletions of entire exons from the mature mRNA. These alternative splicing events do not create frameshift mutations but cause a deletion of one or more of the "EGF-like" repeat units from the ppEGF. There is approximately the same homology between the rat and mouse amino acid sequences both in the EGF region and in the other regions of the ppEGF protein. We conclude that, because of this conservation of homology, there may be an important function performed by these other regions of the ppEGF besides their function as a precursor for the EGF protein.
Insights
Researchers cloned rat preproepidermal growth factor (ppEGF) mRNA, revealing alternative splicing and conserved homology. This suggests ppEGF has functions beyond being an epidermal growth factor precursor.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Epidermal growth factor (EGF) plays crucial roles in cell growth and differentiation.
- Preproepidermal growth factor (ppEGF) is the precursor protein to EGF.
- Understanding ppEGF gene structure and expression is vital for comprehending EGF-related biological processes.
Purpose of the Study:
- To clone and sequence the cDNA of rat preproepidermal growth factor (ppEGF) mRNA.
- To investigate potential structural gene variations and alternative splicing events in rat ppEGF.
- To compare the rat ppEGF sequence with its mouse and human counterparts.
Main Methods:
- cDNA cloning and sequencing of rat ppEGF mRNA.
- Bioinformatic analysis of nucleotide and amino acid sequences.
- Comparative sequence analysis between rat, mouse, and human ppEGF.
Main Results:
- Rat ppEGF cDNA is 4,801 nucleotides long, encoding a 1,133 amino acid protein.
- Evidence suggests multiple structural genes for ppEGF and alternative splicing events.
- Alternative splicing leads to deletions of exons, potentially removing EGF-like repeat units without frameshifts.
- High homology exists between rat and mouse ppEGF sequences in both EGF-like and other regions.
Conclusions:
- The rat ppEGF gene exhibits complexity with potential for multiple transcripts due to alternative splicing.
- Conserved homology between rat and mouse ppEGF suggests functional importance of regions beyond the EGF precursor domain.
- Further research is warranted to elucidate the specific functions of these conserved ppEGF regions.