UV induces nucleolar translocation of ING1 through two distinct nucleolar targeting sequences.
The ING1 candidate tumor suppressor is downregulated in a variety of primary tumors and established cancer cell lines. Blocking its expression experimentally promotes unregulated growth in vitro and in vivo, using cell and animal models. Alternative splicing products encode proteins that localize to the nucleus, inhibit cell cycle progression and affect apoptosis in different model systems. Here we show that ING1 proteins translocate to the nucleolus 12-48 h after UV-induced DNA damage. When a small 50 amino acid portion of ING1 was fused to green fluorescent protein, the fusion protein was efficiently targeted to the nucleolus, indicating that ING1 possesses an intrinsic nucleolar targeting sequence (NTS). We mapped this activity to two distinct 4 amino acid regions, which individually direct fused heterologous proteins to the nucleolus. Overexpression of ING1 induced apoptosis of primary fibroblasts in the presence and absence of UV exposure. In contrast, NTS mutants of ING1 that were not targeted to the nucleolus did not efficiently induce apoptosis when overexpressed and instead protected cells from UV-induced apoptosis. Taken together, these results indicate that UV induces ING1 to translocate to the nucleolus and that this translocation may facilitate apoptosis.
Scott
M
M
Department of Biochemistry and Molecular Biology, Faculty of Medicine, The University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada.
Boisvert
F M
FM
Vieyra
D
D
Johnston
R N
RN
Bazett-Jones
D P
DP
Riabowol
K
K
D000595:Amino Acid Sequence; D017209:Apoptosis / Q000528:radiation effects; D018797:Cell Cycle Proteins; D002466:Cell Nucleolus / Q000378:metabolism* / Q000528:radiation effects*; D002478:Cells, Cultured; D016384:Consensus Sequence; D004249:DNA Damage / Q000528:radiation effects; D004268:DNA-Binding Proteins; D005347:Fibroblasts; D019084:Fluorescent Antibody Technique, Indirect; D015696:Gene Products, tat / Q000235:genetics / Q000378:metabolism; D016147:Genes, Tumor Suppressor / Q000235:genetics; D006801:Humans; D000076023:Inhibitor of Growth Protein 1; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D019913:Nuclear Localization Signals / Q000235:genetics / Q000502:physiology; D009687:Nuclear Proteins; D011485:Protein Binding; D021382:Protein Sorting Signals / Q000235:genetics / Q000502:physiology*; D021381:Protein Transport / Q000528:radiation effects; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012318:RNA Polymerase I / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000528:radiation effects; D014162:Transfection; D025521:Tumor Suppressor Proteins; D014466:Ultraviolet Rays
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D015696:Gene Products, tat; C501503:ING1 protein, human; D000076023:Inhibitor of Growth Protein 1; D047908:Intracellular Signaling Peptides and Proteins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D021382:Protein Sorting Signals; D011506:Proteins; D011993:Recombinant Fusion Proteins; D025521:Tumor Suppressor Proteins; D012318:RNA Polymerase I