Homodimer of two F-box proteins betaTrCP1 or betaTrCP2 binds to IkappaBalpha for signal-dependent ubiquitination.
We found previously that overexpression of an F-box protein betaTrCP1 and the structurally related betaTrCP2 augments ubiquitination of phosphorylated IkappaBalpha (pIkappaBalpha) induced by tumor necrosis factor-alpha (TNF-alpha), but the relationship of the two homologous betaTrCP proteins remains unknown. Herein we reveal that deletion mutants of betaTrCP1 and betaTrCP2 lacking the F-box domain suppressed ubiquitination and destruction of pIkappaBalpha as well as transcriptional activation of NF-kappaB. The ectopically expressed betaTrCP1 and betaTrCP2 formed both homodimer and heterodimer complexes without displaying the trimer complex. Dimerization of betaTrCP1 and/or betaTrCP2 takes place at their conserved NH(2)-terminal regions, termed a "D-domain" (for dimerization domain), located upstream of the F-box domain. The D-domain was necessary and sufficient for the dimer formation. Intriguingly, the betaTrCP homodimer, but not the heterodimer, was selectively recruited to pIkappaBalpha induced by TNF-alpha. These results indicate that not only betaTrCP1 but also betaTrCP2 participates in the ubiquitination-dependent destruction of IkappaBalpha by forming SCF(betaTrCP1-betaTrCP1) and SCF(betaTrCP2-betaTrCP2) ubiquitin-ligase complexes.
Suzuki
H
H
Institute for Drug Discovery Research, Yamanouchi Pharmaceutical Company Ltd., 21 Miyukigaoka, Tsukuba-shi, Ibaraki, 305-8585, Japan.
Chiba
T
T
Suzuki
T
T
Fujita
T
T
Ikenoue
T
T
Omata
M
M
Furuichi
K
K
Shikama
H
H
Tanaka
K
K
D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019281:Dimerization; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D020672:I-kappa B Proteins; D016296:Mutagenesis; D000072000:NF-KappaB Inhibitor alpha; D011485:Protein Binding; D017384:Sequence Deletion; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases; D014452:Ubiquitins / Q000378:metabolism*; D044844:beta-Transducin Repeat-Containing Proteins
C471644:BTRC protein, human; D017931:DNA Primers; D004268:DNA-Binding Proteins; C471645:FBXW11 protein, human; D020672:I-kappa B Proteins; C000606204:NFKBIA protein, human; D014452:Ubiquitins; D044844:beta-Transducin Repeat-Containing Proteins; D000072000:NF-KappaB Inhibitor alpha; D044767:Ubiquitin-Protein Ligases; D019204:GTP-Binding Proteins