RESUMO
An interferon-induced 17 kDa protein has been partially purified from the membranes of interferon-beta-treated Daudi cells. A fraction containing the 17 kDa protein purified 200 fold causes an inhibition of growth of Daudi, Namalva and Hela cells. The same fraction purified from the membranes of untreated cells causes no inhibition of cell growth. This interferon-beta-induced protein is located on the exterior of Daudi cells for it can be labeled with [125I] iodine catalyzed by lactoperoxidase. These results suggest that interferons induce a cell surface protein whose role is to cause an inhibition of cell growth.
Assuntos
Divisão Celular , Interferon Tipo I/farmacologia , Proteínas de Membrana/fisiologia , Linhagem Celular , Células HeLa/citologia , Humanos , Cinética , Proteínas de Membrana/biossíntese , Proteínas de Membrana/isolamento & purificação , Peso MolecularRESUMO
We have isolated a cDNA clone for an interferon-induced 15-kDa protein. The cDNA clone was prepared from mRNA isolated from interferon-beta-treated human Daudi cells. The clone of 635 base pairs contains an open reading frame coding for a protein of 145 amino acids, and suggests for the mRNA a 75-base pair 5' untranslated and a 125-base pair 3' untranslated region. Approximately 85% of the amino acid sequence of the 15-kDa protein has been independently obtained from 2 nmol of material using microsequencing technology on the N terminus of the intact protein and on tryptic and chymotryptic peptides. The amino acid sequence of the isolated protein is identical to the amino acid sequence deduced from the cDNA. Northern blot analysis confirmed that the mRNA for the 15-kDa protein is undetectable in untreated cells, but is greatly induced following interferon treatment.
Assuntos
Clonagem Molecular , DNA/isolamento & purificação , Genes/efeitos dos fármacos , Interferon gama/farmacologia , Proteínas/análise , Sequência de Aminoácidos , Sequência de Bases , Linfoma de Burkitt , Linhagem Celular , Quimotripsina , Humanos , Peso Molecular , Fragmentos de Peptídeos/análise , RNA Mensageiro/genética , RNA Mensageiro/isolamento & purificação , TripsinaRESUMO
Interferons (IFNs)-alpha and -beta but not -gamma enhance the synthesis of a protein in the membranes of Daudi cells. This protein has an estimated molecular weight of 20,000 (20 kD). Furthermore, the 20-kD protein is enhanced only in the membranes of cells whose growth can be inhibited by IFN-beta (Daudi, WISH, HL-60, diploid fibroblasts) but not in the membranes of cells whose growth is not inhibited by IFN-beta (Namalva, Raji). These data suggest a correlation between the IFN-beta-enhanced 20-kD membrane protein and the inhibition of cell growth by IFN-beta.
Assuntos
Divisão Celular/efeitos dos fármacos , Interferon Tipo I/farmacologia , Proteínas de Membrana/biossíntese , Linfoma de Burkitt/metabolismo , Células Cultivadas , Humanos , Peso MolecularRESUMO
Human interferons induce a protein of 15,000 daltons in human and bovine cells. This protein is located in the cytoplasm in a soluble form and is induced by concentrations of interferon which induce the antiviral state. Messenger RNA prepared from interferon-treated human and bovine cells contains a mRNA which yields on translation in vitro a protein similar in size to the 15-kDa protein induced by interferon in vivo. The human protein has been purified to homogeneity from interferon-treated human cells by ion-exchange chromatography and reverse-phase high-performance liquid chromatography. A comparison of the peptides generated by V8 protease from the human and bovine 15-kDa proteins reveals that the two proteins are similar but not identical.