A putative silencer element in the IL-5 gene recognized by Bcl6.
The Bcl6 gene is ubiquitously expressed in adult murine tissues and its product functions as a sequence-specific transcriptional repressor. Bcl6-deficient mice displayed eosinophilic inflammation caused by overproduction of Th2 cytokines. The regulatory mechanism of those cytokine productions by Bcl6 is controversial. When CD4(+) T cells from Bcl6-deficient and lck-Bcl6-transgenic mice were stimulated with anti-CD3 Abs, production of IL-5 among Th2 type cytokines was preferentially affected by the amount of Bcl6 in the T cells. We found a putative Bcl6-binding sequence (IL5BS) on the 3' untranslated region in the murine and human IL-5 genes, and specific binding of Bcl6 protein to the sequence was confirmed by gel retardation assay and chromatin immunoprecipitation assay. The binding activity of endogenous Bcl6 was transiently diminished in Th2 but not in Th1 clones after anti-CD3 stimulation. The exogenous Bcl6 repressed expression of the reporter gene with the IL5BS in K562 cells and the repressor activity was lost by a point mutation of the IL5BS. Furthermore, the IL5BS was required for Bcl6 to repress expression of the IL-5 cDNA. Thus, the IL5BS may act as a silencer element for Bcl6 to repress expression of the IL-5 gene.
Arima
Masafumi
M
Department of Developmental Genetics (H2), Graduate School of Medicine, Chiba University, Chiba, Japan.
Toyama
Hirochika
H
Ichii
Hirohito
H
Kojima
Satoko
S
Okada
Seiji
S
Hatano
Masahiko
M
Cheng
Gang
G
Kubo
Masato
M
Fukuda
Takeshi
T
Tokuhisa
Takeshi
T
D016475:3T3 Cells; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001483:Base Sequence; D017252:CD3 Complex / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D020868:Gene Silencing / Q000276:immunology*; D006801:Humans; D015848:Interleukin-5 / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D020014:K562 Cells; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D011485:Protein Binding / Q000276:immunology; D011518:Proto-Oncogene Proteins / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D051560:Proto-Oncogene Proteins c-bcl-6; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology; D020218:Response Elements / Q000276:immunology*; D014157:Transcription Factors / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D014162:Transfection
D000911:Antibodies, Monoclonal; D017252:CD3 Complex; D004268:DNA-Binding Proteins; D015848:Interleukin-5; D011518:Proto-Oncogene Proteins; D051560:Proto-Oncogene Proteins c-bcl-6; D012097:Repressor Proteins; D014157:Transcription Factors