c-myc is a downstream target of the Smad pathway.
c-Myc is one of the most potent regulators of cell cycle progression in higher eukaryotes. Down-regulation of c-Myc is a critical event for growth inhibition induced by transforming growth factor-beta (TGF-beta) and is frequently impaired in cancer cells. We determined a Smad-responsive element in the c-myc promoter. This element is a complex of the TGF-beta1 inhibitory element (TIE) originally identified in the transin/stromelysin promoter and an E2F site responsible for transcriptional activation of the c-myc promoter. Smad3 and E2F-4 directly bound to the element (TIE/E2F), and substitution of two nucleotides in TIE/E2F impaired binding of both Smad3 and E2F-4 as well as serum-induced activation and TGF-beta-induced suppression of the c-myc promoter activity. Smads bound TIE/E2F within 1 h after stimulation with TGF-beta, before the suppression of c-myc transcription, whereas binding of p130 to TIE/E2F became augmented later than 12 h. TGF-beta signaling did not compete with E2F-4 for binding to TIE/E2F, but reduced p300 co-immunoprecipitating with E2F-4. Therefore, TGF-beta signaling may suppress c-myc promoter activity by dissociating p300 from E2F-4.
Yagi
Ken
K
Department of Biochemistry, The Cancer Institute of the Japanese Foundation for Cancer Research and Research for the Future Program, Japan Society for the Promotion of Science, 1-37-1 Kami-ikebukuro, Toshima-ku, Tokyo 170-8455, Japan.
Furuhashi
Masao
M
Aoki
Hiromasa
H
Goto
Daisuke
D
Kuwano
Hiroyuki
H
Sugamura
Kazuo
K
Miyazono
Kohei
K
Kato
Mitsuyasu
M
D000818:Animals; D019556:COS Cells; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins / Q000378:metabolism*; D050684:E2F Transcription Factors; D050704:E2F4 Transcription Factor; D016259:Genes, myc; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D020218:Response Elements; D016160:Retinoblastoma Protein / Q000378:metabolism; D051899:Smad2 Protein; D051900:Smad3 Protein; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050704:E2F4 Transcription Factor; C493762:E2F4 protein, human; D009687:Nuclear Proteins; D016160:Retinoblastoma Protein; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D015534:Trans-Activators; D014157:Transcription Factors; D016212:Transforming Growth Factor beta