Tax responsiveness of the GM-CSF promoter is mediated by mitogen-inducible sequences other than kappa B.
The mechanism by which the human T-cell leukemia viruses type I and II (HTLV-I and -II) transform T cells is unknown, but the nonstructural Tax protein that these viruses produce is known to be essential for viral replication and to have the capacity to trans-activate cellular gene expression. The HTLV-I and -II Tax proteins have been shown to activate the promoter of both the human and mouse granulocyte-macrophage colony-stimulating factor (GM-CSF) genes in mature T-cell lines. T-cell-specific Tax-responsive sequences were previously localized to the 90-bp region extending from base pairs -53 to +37 in the human GM-CSF promoter. In this study, a series of site-directed and deletion mutations were created in the human GM-CSF promoter, which was linked to the chloramphenicol acetyltransferase (CAT) gene, and the constructs were assayed for their response to Tax by using a Tax-expressing plasmid in transient cotransfection assays. The results demonstrated that both copies of the repeated sequence CATTA (A/T), located between base pairs -48 and -36, are required for Tax responsiveness in T cells and that these sequences bind nuclear factors present in T cells. The Tax-responsiveness of other sequences located 5' of base pair -53 was also examined, including an NF-kappa B consensus sequence and the CK1, CK2, and GC-rich regions identified in both the mouse and human GM-CSF promoters. These sequences did not have Tax-responsive regulatory activity when they were examined in the context of the intact human GM-CSF promoter in T cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Nimer
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Department of Medicine, UCLA School of Medicine 90024-1678.
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D016356:Gene Products, tax / Q000502:physiology*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics*; D008969:Molecular Sequence Data; D010835:Phytohemagglutinins; D011401:Promoter Regions, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015533:Transcriptional Activation
D016356:Gene Products, tax; D010835:Phytohemagglutinins; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D013755:Tetradecanoylphorbol Acetate