Accumulation of polyubiquitinated proteins by overexpression of RBCC protein interacting with protein kinase C2, a splice variant of ubiquitin ligase RBCC protein interacting with protein kinase C1.
The nuclear-cytoplasmic shuttling protein RBCC protein interacting with protein kinase C1 (RBCK1) possesses transcriptional and ubiquitin ligase activities. We have recently reported that RBCC protein interacting with protein kinase C2 (RBCK2), a RING-in-between-RING fingers domain-lacking splice variant of RBCK1, lacks transcriptional activity, but rather represses the RBCK1-mediated transcriptional activity as a cytoplasmic tethering protein for RBCK1. In this study, we have found that RBCK2 overexpressed in human embryonic kidney 293 cells interacts with the polyubiquitin chain and the polyubiquitin-interacting subunit S5a, and significantly increases the intracellular amount of polyubiquitinated proteins. These results strongly suggested that RBCK2 functions as an adaptor protein for the polyubiquitinated protein and the S5a subunit in 26S proteasome through its novel zinc finger motif and ubiquitin-like domain, respectively, presumably delivering the polyubiquitinated proteins to the entrance of the 26S proteasome catalytic domain for degradation.
Department of Structural Molecular Biology, Institute of Scientific and Industrial Research, Osaka University, Japan.
Nobuo
N
Yoshimoto
Kenji
K
Tatematsu
Toshihide
T
Okajima
Katsuyuki
K
Tanizawa
Shun'ichi
S
Kuroda
D000595:Amino Acid Sequence; D002478:Cells, Cultured; D006801:Humans; D008969:Molecular Sequence Data; D046988:Proteasome Endopeptidase Complex / Q000032:analysis / Q000502:physiology; D011506:Proteins / Q000378:metabolism*; D012326:RNA Splicing; D016601:RNA-Binding Proteins; D014157:Transcription Factors / Q000032:analysis / Q000502:physiology*; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases
C498506:PSMD4 protein, human; D011506:Proteins; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D025801:Ubiquitin; C504507:RBCK1 protein, human; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease