Binding of YY1 and Oct1 to a novel element that downregulates expression of IL-5 in human T cells.
BACKGROUND
IL-5 controls development of eosinophilia and has been shown to be involved in the pathogenesis of allergic diseases. In both atopic and nonatopic asthma, elevated IL-5 has been detected in peripheral blood and the airways. IL-5 is produced mainly by activated T cells, and its expression is regulated at the transcriptional level.


OBJECTIVE
This study focuses on the functional analysis of the human IL-5 (hIL-5) promoter and characterization of cis -regulatory elements and transcription factors involved in the suppression of IL-5 transcription in T cells.


METHODS
Methods used in this study include DNase I footprint assays, electrophoretic mobility shift assays, and functional analysis by mammalian cell transfection involving deletion analysis and site-directed mutagenesis.


RESULTS
We identified 5 protein binding regions (BRs) located within the proximal hIL-5 promoter. Functional analysis indicates that the BRs are involved in control of hIL-5 promoter activity. Two of these regions, BR3 and BR4 located at positions -102 to -73, have not previously been described as regulators of IL-5 expression in T cells. We show that the BR3 sequence contains a novel negative regulatory element located at positions -90 to -79 of the hIL-5 promoter, which binds Oct1, octamer-like, and YY1 nuclear factors. Substitution mutations, which abolished binding of these proteins to the BR3 sequence, significantly increased hIL-5 promoter activity in activated T cells.


CONCLUSIONS
We suggest that Oct1, YY1, and octamer-like factors binding to the -90/-79 sequence within the proximal IL-5 promoter are involved in suppression of IL-5 transcription in T cells.
Mordvinov
V A
VA
TVW Telethon Institute for Child Health Research, Perth, Australia.
Schwenger
G T
GT
Fournier
R
R
De Boer
M L
ML
Peroni
S E
SE
Singh
A D
AD
Karlen
S
S
Holland
J W
JW
Sanderson
C J
CJ
D001483:Base Sequence; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000502:physiology*; D015536:Down-Regulation; D050981:Erythroid-Specific DNA-Binding Factors; D005786:Gene Expression Regulation; D051863:Host Cell Factor C1; D006801:Humans; D015848:Interleukin-5 / Q000235:genetics*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000502:physiology; D050811:Octamer Transcription Factor-1; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA; D013601:T-Lymphocytes / Q000378:metabolism*; D014157:Transcription Factors / Q000502:physiology*; D050986:YY1 Transcription Factor
D004268:DNA-Binding Proteins; D050981:Erythroid-Specific DNA-Binding Factors; C497692:HCFC1 protein, human; D051863:Host Cell Factor C1; D015848:Interleukin-5; D009687:Nuclear Proteins; D050811:Octamer Transcription Factor-1; C494165:POU2F1 protein, human; D014157:Transcription Factors; D050986:YY1 Transcription Factor; C494698:YY1 protein, human