Degradation of Tob1 mediated by SCFSkp2-dependent ubiquitination.
Tob1, a member of the Tob/BTG family, is involved in the control of G(1)-S progression by suppressing cyclin D1 expression and acts as a tumor suppressor gene. Tob1 was reported to have a quick turnover through the ubiquitin-proteasome pathway, but proteins involved in this process are still unknown. We showed that Skp2, a substrate-targeting subunit of the SCF (Skp1/Cul1/F-box protein) ubiquitin ligase complex, was involved in ubiquitin-dependent degradation of Tob1. Skp2 interacted with Tob1 and facilitated ubiquitination of Tob1 in intact cells as well as in vitro. Skp2 mutants without the F-box or leucine rich repeat were not able to bind to Tob1 and did not enhance ubiquitination of Tob1. Tob1 was stabilized in both Skp2(-/-) mouse fibroblasts and Skp2 knockdown HeLa cells. Moreover, cyclin D1 expression was suppressed in Skp2 knockdown HeLa cells. These data suggest that Tob1 is a novel target for degradation by the SCF-Skp2 ubiquitin ligase.
Hiramatsu
Yoshihiro
Y
Second Department of Surgery, Hamamatsu University School of Medicine, Hamamatsu, Japan.
Kitagawa
Kyoko
K
Suzuki
Toru
T
Uchida
Chiharu
C
Hattori
Takayuki
T
Kikuchi
Hirotoshi
H
Oda
Toshiaki
T
Hatakeyama
Shigetsugu
S
Nakayama
Keiichi I
KI
Yamamoto
Tadashi
T
Konno
Hiroyuki
H
Kitagawa
Masatoshi
M
D002453:Cell Cycle; D002460:Cell Line; D019938:Cyclin D1 / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D007668:Kidney; D034622:RNA Interference; D011994:Recombinant Proteins / Q000378:metabolism; D044786:S-Phase Kinase-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D019089:Stem Cell Factor / Q000378:metabolism; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*
D047908:Intracellular Signaling Peptides and Proteins; D011994:Recombinant Proteins; D044786:S-Phase Kinase-Associated Proteins; D019089:Stem Cell Factor; C098669:TOB1 protein, human; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin; D019938:Cyclin D1