Nuclear-cytoplasmic shuttling of a RING-IBR protein RBCK1 and its functional interaction with nuclear body proteins.
The intracellular localization of a RING-IBR protein, RBCK1, possessing DNA binding and transcriptional activities, has been investigated. The endogenous RBCK1 was found in both the cytoplasm and nucleus. Particularly in the nucleus, it was localized in the granular structures, most likely nuclear bodies. In contrast, the over-expressed RBCK1 was detected exclusively in the cytoplasm. When the cells were treated with leptomycin B, the over-expressed RBCK1 accumulated in the nuclear bodies. These results suggest that RBCK1 possesses the signal sequences responsible for the nuclearcytoplasmic translocation. Mutational analysis of RBCK1 has indicated that an N-terminal region containing Leu-142 and Leu-145 and a C-terminal one containing the RING-IBR domain serve as the nuclear export and localization signals, respectively. Thus, RBCK1 is a transcription factor dynamically shuttling between cytoplasm and nucleus. Furthermore, RBCK1 was found to interact with nuclear body proteins, CREB-binding protein (CBP), and promyelocytic leukemia protein (PML). Coexpression of RBCK1 with CBP significantly enhanced the transcriptional activity of RBCK1. Although PML per se showed no effect on the transcriptional activity of RBCK1, the CBP-enhanced activity was repressed by coexpression with PML, presumably through the interaction of PML and CBP. Taken together, our data demonstrate that RBCK1 is involved in transcriptional machinery in the nuclear bodies, and its transcriptional activity is regulated by nucleocytoplasmic shuttling.
Tatematsu
Kenji
K
Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Japan.
Yoshimoto
Nobuo
N
Koyanagi
Tomoyoshi
T
Tokunaga
Chiharu
C
Tachibana
Taro
T
Yoneda
Yoshihiro
Y
Yoshida
Minoru
M
Okajima
Toshihide
T
Tanizawa
Katsuyuki
K
Kuroda
Shun'ichi
S
D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D004252:DNA Mutational Analysis; D015536:Down-Regulation; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D005982:Glutathione Transferase / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D007930:Leucine / Q000737:chemistry; D008156:Luciferases / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000502:physiology*; D009687:Nuclear Proteins / Q000378:metabolism; D009842:Oligopeptides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D000071156:Promyelocytic Leukemia Protein; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D025521:Tumor Suppressor Proteins; D015854:Up-Regulation
D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D009842:Oligopeptides; D000071156:Promyelocytic Leukemia Protein; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C489276:protein kinase C-binding protein Beta15, rat; C070576:PML protein, human; D049452:Green Fluorescent Proteins; D008156:Luciferases; D005982:Glutathione Transferase; D007930:Leucine