The oncoprotein gankyrin interacts with RelA and suppresses NF-kappaB activity.
Gankyrin is an oncoprotein commonly overexpressed in hepatocellular carcinomas. It interacts with multiple proteins and accelerates degradation of tumor suppressors Rb and p53. Since gankyrin consists of 7 ankyrin repeats and is structurally similar to IkappaBs, we investigated its interaction with NF-kappaB. We found that gankyrin directly binds to RelA. In HeLa and 293 cells, overexpression of gankyrin suppressed the basal as well as TNFalpha-induced transcriptional activity of NF-kappaB, whereas down-regulation of gankyrin increased it. Gankyrin did not affect the NF-kappaB DNA-binding activity or nuclear translocation of RelA induced by TNFalpha in these cells. Leptomycin B that inhibits nuclear export of RelA suppressed the NF-kappaB activity, which was further suppressed by gankyrin. The inhibitory effect of gankyrin was abrogated by nicotinamide as well as down-regulation of SIRT1, a class III histone deacetylase. Thus, gankyrin binds to NF-kappaB and suppresses its activity at the transcription level by modulating acetylation via SIRT1.
Higashitsuji
Hiroaki
H
Department of Clinical Molecular Biology, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawaharacho, Sakyo-ku, Kyoto 606-8507, Japan. hhigashi@virus.kyoto-u.ac.jp
Higashitsuji
Hisako
H
Liu
Yu
Y
Masuda
Tomoko
T
Fujita
Takanori
T
Abdel-Aziz
H Ismail
HI
Kongkham
Supranee
S
Dawson
Simon
S
John Mayer
R
R
Itoh
Yoshito
Y
Sakurai
Toshiharu
T
Itoh
Katsuhiko
K
Fujita
Jun
J
D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D024202:Electrophoretic Mobility Shift Assay; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D016898:Interferon-alpha / Q000494:pharmacology; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D009536:Niacinamide / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D056564:Sirtuin 1; D037761:Sirtuins / Q000235:genetics / Q000378:metabolism; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection
D005231:Fatty Acids, Unsaturated; D016898:Interferon-alpha; D016328:NF-kappa B; C403591:PSMD10 protein, human; D011518:Proto-Oncogene Proteins; C498143:RELA protein, human; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D051996:Transcription Factor RelA; D049452:Green Fluorescent Proteins; D009536:Niacinamide; D008156:Luciferases; D046988:Proteasome Endopeptidase Complex; C447939:SIRT1 protein, human; D056564:Sirtuin 1; D037761:Sirtuins; C038753:leptomycin B