Abstract
Epithelin/granulin growth factor is synthesized as a 593 amino acid precursor protein that contains 7.5 imperfectly conserved repeats of approximately 57 amino acids. Processed epithelin/granulin peptides have been isolated from vertebrate/invertebrate species and are growth factors implicated in epithelial and haemic cell function. Here they are identified as Human Immunodeficiency Virus (HIV) Tat binding proteins using the yeast two-hybrid assay. Intracellularly in yeast, mutation of selected cysteines in an epithelin/granulin dimeric repeat caused loss of binding to Tat exon 1. In vitro binding of HIV-1 and HIV-2 Tat to epithelin/granulin dimeric and monomeric repeats was also observed by GST-glutathione bead "pulldown" assays. Because Tat is actively secreted from HIV-infected cells and has been shown to serve as a mitogenic factor for angiogenesis and for Kaposi-like cells, our observations suggest that epithelin/granulin growth factors may function as biologically important extracellular Tat co-factors.
Copyright 1999 Academic Press.
MeSH terms
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Amino Acid Sequence
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Amino Acid Substitution
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Binding Sites
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Conserved Sequence / genetics
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Cysteine / genetics
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Cysteine / metabolism
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Exons / genetics
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Gene Library
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Gene Products, tat / genetics
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Gene Products, tat / metabolism*
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Granulins
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Growth Substances / genetics
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Growth Substances / metabolism*
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HIV-1 / genetics
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HIV-1 / metabolism*
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HIV-2 / genetics
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HIV-2 / metabolism*
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Humans
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Intercellular Signaling Peptides and Proteins*
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Leukocytes, Mononuclear / metabolism
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Molecular Sequence Data
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism
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Protein Binding
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RNA, Messenger / analysis
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RNA-Binding Proteins
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Saccharomyces cerevisiae / genetics
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Sequence Deletion
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Serine-Arginine Splicing Factors
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Tumor Cells, Cultured
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Viral Proteins / genetics
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Viral Proteins / metabolism
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tat Gene Products, Human Immunodeficiency Virus
Substances
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Gene Products, tat
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Granulins
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Growth Substances
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Intercellular Signaling Peptides and Proteins
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Nuclear Proteins
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RNA, Messenger
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RNA-Binding Proteins
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Recombinant Fusion Proteins
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Viral Proteins
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tat Gene Products, Human Immunodeficiency Virus
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Serine-Arginine Splicing Factors
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Cysteine