title: The human SNF5/INI1 protein facilitates the function of the growth arrest and DNA damage-inducible protein (GADD34) and modulates GADD34-bound protein phosphatase-1 activity.
abstract: The growth arrest and DNA damage-inducible protein (GADD34) mediates growth arrest and apoptosis in response to DNA damage, negative growth signals, and protein malfolding. GADD34 binds to protein phosphatase-1 (PP1) and can attenuate translational elongation of key transcriptional factors through dephosphorylation of eukaryotic initiation factor-2alpha. We reported previously that the human trithorax leukemia fusion protein (HRX) can bind to GADD34 and abrogate GADD34-mediated apoptosis in response to UV irradiation. We found that hSNF5/INI1, a component of the hSWI/SNF chromatin remodeling complex, also binds to GADD34 and can coexist with GADD34 and HRX fusion proteins as a trimolecular complexes in vivo. In the present report, we demonstrate that hSNF5/INI1 binds to GADD34 in part through the PP1 docking site within a domain homologous to herpes simplex virus-1 ICP34.5. We found that hSNF5/INI1 can bind PP1 independently and weakly stimulate its phosphatase activity in solution and in complex with GADD34. hSNF5/INI1 and PP1 do not compete for binding to GADD34 but rather form a stable heterotrimeric complex with GADD34. We also show that Epstein-Barr nuclear protein 2, which binds hSNF5/INI1, can disrupt hSNF5/INI1 binding to GADD34 and partially reverse the GADD34-mediated growth suppression function in Ha-ras expressing HIH-3T3 (3T3-ras) cells. These results implicate hSNF5/INI1 in the function of GADD34 and suggest that hSNF5/INI1 may regulate PP1 activity in vivo.
authors.affiliation: Division of Medical Oncology, Department of Medicine, Veterans Administration Puget Sound Health Care System, Seattle Division, Seattle, Washington 98108, USA. danielw@u.washington.edu
authors.forename: Daniel Y
authors.initials: DY
authors.lastname: Wu
authors.forename: Douglas C
authors.initials: DC
authors.lastname: Tkachuck
authors.forename: Rachel S
authors.initials: RS
authors.lastname: Roberson
authors.forename: William H
authors.initials: WH
authors.lastname: Schubach
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D000943:Antigens, Differentiation; D001665:Binding Sites; D018797:Cell Cycle Proteins; D002455:Cell Division; D002460:Cell Line; D002470:Cell Survival; D002868:Chromosomal Proteins, Non-Histone; D003001:Cloning, Molecular; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D054645:Protein Phosphatase 1; D011506:Proteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D000071796:SMARCB1 Protein; D014157:Transcription Factors; D014162:Transfection
chemical_list: D000943:Antigens, Differentiation; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D010446:Peptide Fragments; D011506:Proteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D000071796:SMARCB1 Protein; C513266:SMARCB1 protein, human; C513265:Smarcb1 protein, mouse; D014157:Transcription Factors; C087519:PPP1R15A protein, human; D010749:Phosphoprotein Phosphatases; C513256:Ppp1r15a protein, mouse; D054645:Protein Phosphatase 1