Differential effect of HTLV infection and HTLV Tax on interleukin 3 expression.
To characterize the interactions between human T-cell leukemia virus (HTLV) infection and cellular gene expression, we examined the expression of the lymphokine interleukin 3 (IL-3) in the presence and absence of HTLV infection. IL-3, like granulocyte-macrophage colony-stimulating factor (GM-CSF), is produced by activated but not resting T cells, but although GM-CSF is constitutively expressed in HTLV-infected T cells IL-3 mRNA cannot be detected in either unstimulated or mitogen-stimulated HTLV-infected cells by polymerase chain reaction (PCR) analysis. In contrast, transient co-transfection studies with an IL-3 promoter-CAT reporter gene and an HTLV-II Tax expression construct demonstrate that Tax can transactivate the IL-3 promoter in HTLV-uninfected T cells. To determine whether differences in IL-3 promoter-binding proteins present in HTLV-infected and uninfected T cells account for this discrepancy, DNAase I footprinting of the IL-3 promoter was performed. Although crude nuclear extracts from both cell types protected the IL-3 sequences located between base pairs -168 and -125, the sequences between -125 and -103, which contain the lymphokine consensus sequences CK-1 and CK-2, were protected by extracts from HTLV-infected but not HTLV-uninfected T cells. Deletion of the region containing the CK-1 and CK-2 sequences from an IL-3 promoter CAT construct resulted in a sixfold rise in promoter activity in HTLV-infected but not uninfected T-cell lines, indicating that this region participates in the repression of IL-3 gene expression in HTLV-infected T cells.
Department of Medicine, UCLA School of Medicine 90024-1678.
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Wolin
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Kornuc
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C
Hong
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Shin
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Lee
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Lau
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Nimer
D001483:Base Sequence; D002460:Cell Line; D003850:Deoxyribonuclease I / Q000494:pharmacology; D015870:Gene Expression; D016356:Gene Products, tax / Q000502:physiology*; D015368:Human T-lymphotropic virus 1 / Q000502:physiology*; D006801:Humans; D007377:Interleukin-3 / Q000235:genetics*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D013601:T-Lymphocytes / Q000378:metabolism / Q000382:microbiology*
D016356:Gene Products, tax; D007377:Interleukin-3; D012333:RNA, Messenger; D003850:Deoxyribonuclease I