Human T-cell leukemia virus type I Tax transactivates the promoter of human prointerleukin-1beta gene through association with two transcription factors, nuclear factor-interleukin-6 and Spi-1.
The human T-cell leukemia virus type I (HTLV-I), which infects a wide variety of mammalian cells including monocytes and macrophages, encodes a transactivating protein designated as Tax. We now report that Tax induces the human prointerleukin-1beta (IL1B) gene promoter in monocytic cells. In our transient transfection assays using human THP-1 monocytic cells, a chloramphenicol acetyltransferase (CAT) construct containing the IL1B promoter sequence between positions -131 and +12 showed an approximately 90-fold increase in activity following cotransfection of a Tax expression vector. Moreover, Tax synergized with lipopolysaccharide (LPS) to induce the IL1B promoter activity. Analyses of specific nucleotide substitutions further indicated that the Tax-induced transcriptional activation requires two transcription factor binding motifs within the IL1B promoter; one is a binding site for nuclear factor (NF)-IL6 (CCAAT/enhancer binding protein beta, C/EBP beta), which belongs to the basic region-leucine zipper (bZIP) family and the other for Spi-1 (PU.1), which is an Ets family protein found principally in monocytes, macrophages, and B lymphocytes. In electrophoretic mobility shift assays (EMSA) using in vivo THP-1 nuclear extracts, Tax expression in THP-1 monocytic cells significantly increased binding of the two factors to their target IL1B promoter sequences. However, in contrast to NF-IL6 and Spi-1, DNA binding activity of Oct-1, an ubiquitously expressed octamer-binding protein was not affected by Tax. Additional EMSA using in vitro translated proteins also showed that recombinant Tax enhances DNA binding of both of recombinant NF-IL6 and Spi-1 proteins. These data were supported by our glutathione S-transferase (GST)-pull-down data, which indicated that Tax physically interacts with the two proteins. Based on the results obtained from the present study, we conclude that the IL1B promoter is a Tax-responsive sequence as a result of ability of Tax to induce binding of NF-IL6 and Spi-1 to the IL1B promoter sequence through protein-protein interaction.
Tsukada
J
J
First Department of Internal Medicine, School of Medicine and the School of Health Sciences, University of Occupational and Environmental Health, Kitakyushu, Japan.
Misago
M
M
Serino
Y
Y
Ogawa
R
R
Murakami
S
S
Nakanishi
M
M
Tonai
S
S
Kominato
Y
Y
Morimoto
I
I
Auron
P E
PE
Eto
S
S
D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D016356:Gene Products, tax / Q000378:metabolism*; D051863:Host Cell Factor C1; D015368:Human T-lymphotropic virus 1; D006801:Humans; D007375:Interleukin-1 / Q000235:genetics*; D009687:Nuclear Proteins / Q000378:metabolism*; D050811:Octamer Transcription Factor-1; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011498:Protein Precursors / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D000099232:Proto-Oncogene Protein Spi-1
D022762:CCAAT-Enhancer-Binding Proteins; D004247:DNA; D004268:DNA-Binding Proteins; D016356:Gene Products, tax; D051863:Host Cell Factor C1; D007375:Interleukin-1; D009687:Nuclear Proteins; D050811:Octamer Transcription Factor-1; D011498:Protein Precursors; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D000099232:Proto-Oncogene Protein Spi-1; C497692:HCFC1 protein, human; C494165:POU2F1 protein, human; C043830:interleukin 1 precursor