title: Oligomerization of human Gadd45a protein.
abstract: Gadd45a is an 18-kDa acidic protein that is induced by genotoxic and certain other cellular stresses. The exact function of this protein is not known. However, there is evidence for its involvement in growth control, maintenance of genomic stability, DNA repair, cell cycle control, and apoptosis. Consistently, Gadd45a has previously been shown to interact in vitro and/or in vivo with a number of proteins playing central roles in these cellular processes: proliferating cell nuclear antigen, p21(Cip1/Waf1), Cdc2-CyclinB complex, MTK1, and histones. Adding to this complexity, we have found that Gadd45a self-associates in solution, both in vitro and when expressed in the cell. Moreover, Gadd45a can complex with the two other members of the Gadd45 family of stress-induced proteins, human Gadd45b (MyD118) and Gadd45g (CR6). Gel-exclusion chromatography, native gel electrophoretic analysis, enzyme-linked immunosorbent assay, and chemical cross-linking showed that recombinant Gadd45a forms dimeric, trimeric, and tetrameric species in vitro, the dimers being the predominant form. Deletion mutant and peptide scanning analyses suggest that Gadd45a has two self-association sites: within N-terminal amino acids 33-61 and within 40 C-terminal amino acids. Despite the low abundance of Gadd45a in the cell, oligomer-forming concentrations can probably be achieved in the foci-like nuclear structures formed by the protein upon overexpression. Evidence for a potential role of Gadd45a self-association in altering DNA accessibility on damaged nucleosomes is presented.
authors.affiliation: NCI, National Institutes of Health, Gene Response Section, Bethesda, Maryland 20892, USA.
authors.forename: O
authors.initials: O
authors.lastname: Kovalsky
authors.forename: F D
authors.initials: FD
authors.lastname: Lung
authors.forename: P P
authors.initials: PP
authors.lastname: Roller
authors.forename: A J
authors.initials: AJ
authors.lastname: Fornace
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D017209:Apoptosis; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002138:Calibration; D018797:Cell Cycle Proteins; D002843:Chromatin / Q000378:metabolism; D002850:Chromatography, Gel; D003432:Cross-Linking Reagents / Q000494:pharmacology; D019926:Cyclin B / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D004247:DNA / Q000737:chemistry; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli / Q000378:metabolism; D017353:Gene Deletion; D006657:Histones / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D008856:Microscopy, Fluorescence; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism*; D009707:Nucleosomes / Q000378:metabolism; D011233:Precipitin Tests; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism*; D011743:Pyrimidines / Q000737:chemistry; D014162:Transfection; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays; D000097642:GADD45 Proteins
chemical_list: D000596:Amino Acids; D016203:CDC2 Protein Kinase; D018797:Cell Cycle Proteins; D002843:Chromatin; D003432:Cross-Linking Reagents; D019926:Cyclin B; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004247:DNA; D006657:Histones; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D009707:Nucleosomes; D018809:Proliferating Cell Nuclear Antigen; D011506:Proteins; D011743:Pyrimidines; D000097642:GADD45 Proteins; C493956:CDKN1A protein, human; C439070:GADD45A protein, human