Transcriptional regulation of the human interleukin-6 gene promoter in human T-cell leukemia virus type I-infected T-cell lines: evidence for the involvement of NF-kappa B.
Freshly isolated leukemic cells from patients with adult T-cell leukemia (ATL) and human T-cell leukemia virus type I (HTLV-I)-infected T-cell lines constitutively produce high levels of interleukin-6 (IL-6) protein and mRNA. To clarify the mechanisms that lead to the activation of IL-6 gene in HTLV-I-infected cells, we first studied the regulatory regions in the IL-6 gene transcription by transfection of chloramphenicol acetyltransferase (CAT) reporter plasmids containing the IL-6 promoter. When transfected into HTLV-I-infected T-cell lines MT-2 and HUT-102, IL-6 promoter/CAT plasmids were strongly activated without any stimulation. By deletion analysis of 5' upstream region of IL-6 promoter, the DNA region between -73 and -59 bp from the transcription start site of IL-6 gene was important in the expression of IL-6/CAT activities in HTLV-I-infected cells. This region contains nuclear factor (NF)-kappa B binding site. The site-directed mutation of the kappa B motif in IL-6/CAT plasmid resulted in the complete abrogation of IL-6 promoter activity in these cells. Furthermore, when IL-6 promoter/CAT plasmid was introduced into an HTLV-I-uninfected T-cell line, Jurkat, IL-6 promoter activity was silent in the basal level, but strongly increased by the cotransfection with an HTLV-I tax expression plasmid. However, tax expression plasmid showed no transactivation activity, when kappa B site was mutated in IL-6 promoter/CAT plasmid. We found that the IL-6 kappa B site specifically formed a complex with NF-kappa B-containing nuclear extracts from MT-2 and HUT-102 cells. Finally, transfection of HTLV-I tax into Jurkat cells resulted in induction of specific binding of nuclear extracts to the NF-kappa B sequence. These results strongly suggest that HTLV-I tax gene may transactivate IL-6 gene through kappa B site in HTLV-I-positive T-cell lines and activation of NF-kappa B may be crucial in HTLV-I-induced IL-6 gene activation in ATL.
Mori
N
N
First Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
Shirakawa
F
F
Shimizu
H
H
Murakami
S
S
Oda
S
S
Yamamoto
K
K
Eto
S
S
D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers / Q000737:chemistry; D015967:Gene Expression Regulation, Viral; D016356:Gene Products, tax / Q000502:physiology; D016355:Genes, pX; D015490:HTLV-I Infections / Q000235:genetics*; D006801:Humans; D066298:In Vitro Techniques; D015850:Interleukin-6 / Q000235:genetics*; D015458:Leukemia, T-Cell / Q000503:physiopathology; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000502:physiology*; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics; D017384:Sequence Deletion; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000382:microbiology; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D017931:DNA Primers; D016356:Gene Products, tax; D015850:Interleukin-6; D016328:NF-kappa B; D009687:Nuclear Proteins; D012333:RNA, Messenger; D012367:RNA, Viral