Identification and characterization of a radiation-inducible glycosylated human early-response gene.
A radiation-inducible immediate-early gene, IEX-1, was identified and characterized in human squamous carcinoma cells. Sequence analysis revealed 156-amino acid nucleotides, encoding a protein of Mr 20,000. The protein is glycosylated (Mr approximately 27,000) in the presence of microsomal membranes. Northern analysis reveals a 1.2-kb transcript. Treatment with cycloheximide was associated with superinduction of this transcript suggesting that it is an immediate-early gene. The abundance of IEX-1 mRNA increased rapidly after exposure of the cells to ionizing radiation (2-10 Gy), reaching a maximum by 15 min and returning subsequently to basal levels by 4 h. Expression of IEX-1 was also induced significantly by the protein kinase C (PKC) activator 12-O-tetradecanoylphorbol-13-acetate (TPA), the protein phosphatase inhibitor okadaic acid, and tumor necrosis factor-alpha, whereas treatment of cells with UV light and H2O2 had little effect on IEX-1 expression. Cells depleted of PKC by prolonged incubation with TPA showed no attenuated IEX-1 response to tumor necrosis factor-alpha. This is the first report of IEX-1, a radiation-inducible glycosylated human protein, whose expression can be mediated through multisignal transduction pathways.
Kondratyev
A D
AD
Department of Radiation Medicine, Division of Radiation Research, Georgetown University Medical Center, Washington, DC 20007, USA.
Chung
K N
KN
Jung
M O
MO
D000595:Amino Acid Sequence; D051017:Apoptosis Regulatory Proteins; D001483:Base Sequence; D002294:Carcinoma, Squamous Cell / Q000235:genetics*; D018076:DNA, Complementary / Q000032:analysis; D005786:Gene Expression Regulation / Q000528:radiation effects*; D017781:Genes, Immediate-Early / Q000528:radiation effects; D006031:Glycosylation; D006801:Humans; D017874:Immediate-Early Proteins / Q000737:chemistry / Q000235:genetics*; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics*; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D011493:Protein Kinase C / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D051017:Apoptosis Regulatory Proteins; D018076:DNA, Complementary; C099815:IER3 protein, human; D017874:Immediate-Early Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D014409:Tumor Necrosis Factor-alpha; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate