Isolation and Partial Characterization of a New Gene (br1) Belonging to the Superfamily of the Small GTP-Binding Proteins
Several permanent cell lines of epithelial origin are able to grow in culture in the absence of serum components. It was originally proposed by Temin et al. (1972) that such behaviour was dependent on the production of mitogenic factors (MSA or Multiplication Stimulating Activity) . The most studied system is a rat liver cell line BRL 3A isolated by Coon (1968) . Subsequent studies demonstrated that MSA is the rat equivalent of the insulin like growth factor II (IGF-II) (Rechler et al., 1985), but also showed that the ability of this cell line to grow in serum-free medium is independent of the synthesis and secretion of this polypeptide (Nissley et al., 1977) . We have been investigating this system mainly to understand the biological role and the expression and regulation of the IGF-II gene (Chiariotti et al., 1988). In the course of screening several cDNA libraries derived from the BRL 3A cell line we accidentally isolated some cDNA clones abundantly represented in the stable mRNA population, but not related to IGF-II. Subsequent characterization of these clones lead to the discovery that this mRNA code for a protein of molecular weight 22,800 belonging to the superfamily of ras-related genes (Bucci et al., 1988). In the present study we report some aspects of the organization, structure and expression of this novel putative GTP-binding protein.
KeywordsGuanidinium Thiocyanate Permanent Cell Line eDNA Clone Multiplication Stimulate Activity Gene Gene Gene
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