Constitutive expression of a gene encoding a polypeptide homologous to biologically active human platelet protein in Rous sarcoma virus-transformed fibroblasts.

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 CEF4 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-Il) and platelet factor 4 (PF-4). Serum stimulation of quiescent normal CEF results in a rapid but transient expression ofpCEF-4 mRNA. Hence, pCEF-4 mRNA is expressed at the G.-G1 transition and during the first G, 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.Much of our knowledge of the gene products responsible for cell transformation is derived from investigations of the virally encoded oncogenes and of the protooncogenes, their cellular ancestors. Functional and structural similarities often exist between oncogene products and growth factors, growth factor receptors, or the products of other genes expressed during the normal mitogenic response (1). In several instances, the alteration in cellular protooncogenes resulting in their oncogenic activation is understood (1-4). Hence, considerable progress has been accomplished regarding the biochemical characterization of some of the agents that cause cell transformation. In contrast, little is known about the biochemical pathways and cellular activities critically modified during the transformation process. The absence of functional assays and the lack of an appropriate model system amenable to genetic manipulation have clearly limited our progress in this respect. Various approaches have been utilized to circumvent these limitations. One involves the study of protein phosphorylation in normal and transformed cells, because a class of transforming proteins exhibits tyrosine-specific kinase activity. Some investigators have also compared the role of protooncogenes in normal and malignant growth because of the obvious links between this class of genes and the mitogenic response. We have followed a third approach by searching for genes repressed or expressed in response to transforming proteins or growth factors without regard to their possible relationship to known oncogenes.In this report, we describe a cDNA clone (denoted pCEF-4) corresponding to a 1.2-kilobase (kb) mRNA species that is expressed transiently in response to serum and constitutively in Rous sarcoma virus (RSV)-transformed chicken embryo fibroblasts (CEF) in the presence or absence of serum. Increased transcription and stabilization result in the accumulation of the pCEF-4 mRNA in RSV-transformed cells. A polypeptide of Mr 11,000 is predicted by the nucleic...

Wound-factor-induced and cell cycle phase-dependent expression of 9E3/CEF4, the avian gro gene.

“…The effects of "wounding" on 9E3 expression and DNA synthesis To study the effects of wounding on 9E3 expression and DNA synthesis, we performed experiments on starved confluent CEF cultures that are known to express 9E3 only at very low levels (Bedard et al, 1987;Sugano et al, 1987;Martins-Green and Bissell, 1990). These cultures were "wounded" by scraping swaths across the petri dishes as shown in Figure 1A.…”

“…One group, the gro genes, includes JE (Cochran et al, 1983;Takehara et al, 1987), KC (Cochran et al, 1983), melanoma growth stimulating activity (MGSA)/human gro (Richmond et al, 1983(Richmond et al, , 1985Anisowicz et al, 1988;, hamster gro (Anisowicz et al, 1987), and 9E3/ CEF4 (Bedard et al, 1987;Sugano et al, 1987). Oquendo et al (1989) have discussed the close homology between these genes and pointed out that KC, MGSA/human gro, hamster gro, and 9E3/CEF4 are essentially the same gene in mouse, human, hamster, and chicken, respectively.…”

A chicken homolog of mammalian interleukin‐1β : cDNA cloning and purification of active recombinant protein

“…We therefore treated chicken HD-11 cells for various times with 5 µg/ml of LPS and tested the resulting supernatants for the presence of a secreted substance that would induce CXC chemokine RNA in the chicken fibroblast cell line CEC-32. Two chicken cDNAs have been cloned that might code for the chicken homolog of the CXC chemokine IL-8 : 9E3/CEF4 [32,33] and K60 (Sick, C. and Staeheli, P., personal communication). Supernatants from LPSinduced HD-11 cells were found to induce transcripts in CEC-32 cells that hybridized to the K60 cDNA probe in northern blots (Fig.…”

The constitutive activation of the CEF-4/9E3 chemokine gene depends on C/EBPβ in v-src transformed chicken embryo fibroblasts

“…We have previously characterized the constitutive activation of the CEF-4/9E3 chemokine gene in chicken embryo ®broblasts (CEF) transformed by the Rous sarcoma virus (RSV; Bedard et al, 1987a;Cabannes et al, 1997;. CEF-4/ 9E3 encodes a chemokine of the CXC family with extensive amino acid sequence similarity to Interleukin 8 and Gro/MGSA.…”