Novel splice variants of ING4 and their possible roles in the regulation of cell growth and motility.
The ING4 gene is a candidate tumor suppressor gene that functions in cell proliferation, contact inhibition, and angiogenesis. We identified three novel splice variants of ING4 with differing activities in controlling cell proliferation, cell spreading, and cell migration. ING4_v1 (the longest splice variant), originally identified as ING4, encodes an intact nuclear localization signal (NLS), whereas the other three splice variants (ING4_v2, ING4_v3, and ING4_v4) lack the full NLS, resulting in increased cytoplasmic localization of these proteins. We found that one of the three ING4 variants, ING4_v2, is expressed at the same level as the original ING4 (ING4_v1), suggesting that ING4 variants may have significant biological functions. Growth suppressive effects of the variants that have a partial NLS (ING4_v2 and ING4_v4) were attenuated by a weaker effect of the variants on p21(WAF1) promoter activation. ING4_v4 lost cell spreading and migration suppressive effects; on the other hand, ING4_v2 retained a cell migration suppressive effect but lost a cell spreading suppressive effect. Therefore, ING4_v2, which localized primarily into cytoplasm, might have an important role in the regulation of cell migration. We also found that ING4_v4 played dominant-negative roles in the induction of p21(WAF1) promoter activation and in the suppression of cell motility by ING4_v1. In addition, ING4 variants had different binding affinities to two cytoplasmic proteins, protein-tyrosine phosphatase, receptor type, f polypeptide (PTPRF), interacting protein (liprin), alpha1, and G3BP2a. Understanding the functions of the four splice variants may aid in defining their roles in human carcinogenesis.
Unoki
Motoko
M
Laboratory of Human Carcinogenesis, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892, USa.
Shen
Jiang Cheng
JC
Zheng
Zhi-Ming
ZM
Harris
Curtis C
CC
D048868:Adaptor Proteins, Signal Transducing; D017398:Alternative Splicing; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D002465:Cell Movement; D049109:Cell Proliferation; D003114:Colony-Forming Units Assay; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004265:DNA Helicases; D017931:DNA Primers; D019084:Fluorescent Antibody Technique, Indirect; D014644:Genetic Variation; D006131:Growth Inhibitors / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D009369:Neoplasms / Q000378:metabolism / Q000473:pathology; D019913:Nuclear Localization Signals; D010750:Phosphoproteins / Q000378:metabolism; D000075223:Poly-ADP-Ribose Binding Proteins; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D020365:RNA Helicases; D000067776:RNA Recognition Motif Proteins; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D017931:DNA Primers; D006131:Growth Inhibitors; D018398:Homeodomain Proteins; C483230:ING4 protein, human; D016328:NF-kappa B; D019913:Nuclear Localization Signals; C094398:PPFIA1 protein, human; D010750:Phosphoproteins; D000075223:Poly-ADP-Ribose Binding Proteins; D000067776:RNA Recognition Motif Proteins; D025521:Tumor Suppressor Proteins; D004265:DNA Helicases; C116070:G3BP1 protein, human; D020365:RNA Helicases