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Constitutive expression of a gene encoding a polypeptide homologous to biologically active human platelet protein in
P A Bedard1, D Alcorta, D L Simmons
1Department of Cellular and Developmental Biology, Harvard University, Cambridge, MA 02138.
Abstract:
A molecular clone corresponding to a 1.2-kilobase mRNA enriched in Rous sarcoma virus-transformed chicken embryo fibroblasts (CEF) was identified by differential screening of a cDNA library. The induction of the cloned sequence (denoted pCEF-4) in CEF infected by the temperature-sensitive mutant NY72-4 Rous sarcoma virus is rapid and independent of protein synthesis. DNA sequencing of the 1.2-kilobase insert of CEF-4 revealed an open reading frame that predicts an 11-kDa protein. The predicted pCEF-4 gene product is homologous to human connective tissue-activating peptide III (CTAP-III) and platelet factor 4 (PF-4). Serum stimulation of quiescent normal CEF results in a rapid but transient expression of pCEF-4 mRNA. Hence, pCEF-4 mRNA is expressed at the G0-G1 transition and during the first G1 phase of normal CEF reentering the cell cycle. The expression of pCEF-4 mRNA in Rous sarcoma virus-transformed CEF appears to be the result of transcriptional activation and stabilization of the transcript.
Insights
Researchers identified a gene (pCEF-4) rapidly expressed in Rous sarcoma virus-transformed cells. This gene product is similar to human growth factors and is transiently expressed in normal cells re-entering the cell cycle.
Area of Science:
- Molecular Biology
- Cell Biology
- Virology
Background:
- Rous sarcoma virus (RSV) transformation of chicken embryo fibroblasts (CEF) leads to altered gene expression.
- Identifying genes involved in viral transformation and cell cycle regulation is crucial.
Purpose of the Study:
- To identify and characterize novel genes induced during RSV-mediated transformation of CEF.
- To understand the role of the identified gene in cell cycle progression.
Main Methods:
- Differential screening of a cDNA library from RSV-transformed CEF.
- DNA sequencing of the identified clone (pCEF-4).
- Analysis of pCEF-4 mRNA expression in normal and transformed CEF under different conditions.
Main Results:
- A 1.2-kilobase mRNA, pCEF-4, was identified and enriched in RSV-transformed CEF.
- pCEF-4 encodes an 11-kDa protein homologous to human connective tissue-activating peptide III (CTAP-III) and platelet factor 4 (PF-4).
- pCEF-4 mRNA expression is rapidly induced in transformed CEF, independent of protein synthesis, and transiently expressed in normal CEF during G0-G1 transition.
Conclusions:
- pCEF-4 represents a gene rapidly activated by RSV transformation.
- The pCEF-4 gene product's homology suggests roles in cell growth and extracellular matrix interactions.
- pCEF-4 mRNA expression dynamics indicate its involvement in cell cycle re-entry and transformation.