Activation of synoviolin promoter in rheumatoid synovial cells by a novel transcription complex of interleukin enhancer binding factor 3 and GA binding protein alpha.
OBJECTIVE
Synoviolin is an E3 ubiquitin ligase, and its overexpression is implicated in the pathogenesis of rheumatoid arthritis (RA). We reported previously that Ets binding site 1 (EBS-1) within the synoviolin promoter is crucial for the expression of synoviolin, and GA binding protein (GABP) binds to this site. This study was undertaken to elucidate the precise mechanisms of transcriptional regulation via EBS-1.


METHODS
We performed purification and identification of complex components that bind to EBS-1 and inspected their contributions to the transcriptional regulation of synoviolin in rheumatoid synovial cells. We biochemically purified proteins that had EBS-1 binding activity and identified the proteins using liquid chromatography tandem mass spectrometry analysis. The identified proteins were verified to recruit and form the complex on EBS-1 using electrophoretic mobility shift assay and coimmunoprecipitation assay. Furthermore, their transcription activities were tested by reporter assays and RNA interference experiments.


RESULTS
We identified interleukin enhancer binding factor 3 (ILF-3) as a novel factor in the complex. ILF-3 was demonstrated to activate the synoviolin promoter via association with GABPalpha in rheumatoid synovial cells. In addition, further activation was observed with ILF-2 and GABPbeta, previously reported interactants of ILF-3 and GABPalpha, respectively. Moreover, ILF-3-knockdown experiments showed reduced expression of the synoviolin gene.


CONCLUSIONS
Our findings indicate that ILF-3, which has been known to regulate IL-2 expression in T cells, up-regulates synoviolin expression with GABPalpha in rheumatoid synovial cells. ILF-3 might be a target for RA treatment through its effect on IL-2 in T cells and synoviolin in rheumatoid synovial cells.
Izumi
Toshihiko
T
St. Marianna University School of Medicine, Kawasaki, Kanagawa, Japan.
Fujii
Ryoji
R
Izumi
Tomonori
T
Nakazawa
Minako
M
Yagishita
Naoko
N
Tsuchimochi
Kaneyuki
K
Yamano
Yoshihisa
Y
Sato
Tomoo
T
Fujita
Hidetoshi
H
Aratani
Satoko
S
Araya
Natsumi
N
Azakami
Kazuko
K
Hasegawa
Daisuke
D
Kasaoka
Shunji
S
Tsuruta
Ryosuke
R
Yokouti
Masahiro
M
Ijiri
Kosei
K
Beppu
Moroe
M
Maruyama
Ikuro
I
Nishioka
Kusuki
K
Maekawa
Tsuyoshi
T
Komiya
Setsuro
S
Nakajima
Toshihiro
T
D000818:Animals; D001172:Arthritis, Rheumatoid / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D051268:GA-Binding Protein Transcription Factor / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D051379:Mice; D041681:NIH 3T3 Cells; D050779:Nuclear Factor 90 Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D010003:Osteoarthritis / Q000378:metabolism / Q000503:physiopathology; D011401:Promoter Regions, Genetic / Q000502:physiology; D034622:RNA Interference; D013583:Synovial Membrane / Q000166:cytology / Q000502:physiology*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics*
D051268:GA-Binding Protein Transcription Factor; D050779:Nuclear Factor 90 Proteins; D009687:Nuclear Proteins; C482345:SYVN1 protein, human; D044767:Ubiquitin-Protein Ligases