title: Gadd45 is a nuclear cell cycle regulated protein which interacts with p21Cip1.
abstract: GADD45 was originally identified as a cDNA clone induced by growth arrest and DNA damage. We show that Gadd45 is a nuclear protein, widely expressed in normal tissues, particularly in quiescent cellular populations. Using cell synchronisation methods we show that Gadd45 levels are highest in the G1 phase of the cell cycle, and are greatly reduced during S phase. Immunoprecipitation of Gadd45 from mammalian cells reveals that it is tightly associated with a protein which reacts with antibodies to the cyclin dependent kinase inhibitor p21Cip1. Binding of recombinant Gadd45 protein to overlapping p21Cip1 peptides in ELISA assays and use of the yeast two hybrid assay show that Gadd45 directly interacts with this cell cycle inhibitor. These data suggest that Gadd45 may act in the regulation of the cell cycle. It is postulated that the interactions of Gadd45 with both p21Cip1 and PCNA are important for the modulation of cell cycles, and for the inhibition of DNA replication.
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D015153:Blotting, Western; D002453:Cell Cycle / Q000528:radiation effects; D003001:Cloning, Molecular; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D016193:G1 Phase; D005720:Gamma Rays; D006706:Homeostasis; D006801:Humans; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins; D008322:Mammals; D051379:Mice; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D014176:Protein Biosynthesis; D047428:Protein Kinase Inhibitors; D011506:Proteins / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D016196:S Phase; D000097642:GADD45 Proteins
chemical_list: D000906:Antibodies; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D047428:Protein Kinase Inhibitors; D011506:Proteins; D011994:Recombinant Proteins; D000097642:GADD45 Proteins; C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse