Human BAG-1 proteins bind to the cellular stress response protein GADD34 and interfere with GADD34 functions.
The cellular stress response protein GADD34 mediates growth arrest and apoptosis in response to DNA damage, negative growth signals, and protein malfolding. GADD34 binds to protein phosphatase PP1 and can attenuate the translational elongation of key transcriptional factors through dephosphorylation of eukaryotic initiation factor 2alpha (eIF2alpha). Recently, we reported the involvement of human SNF5/INI1 (hSNF5/INI1) protein in the functions of GADD34 and showed that hSNF5/INI1 binds GADD34 and stimulates the bound PP1 phosphatase activity. To better understand the regulatory and functional mechanisms of GADD34, we undertook a yeast two-hybrid screen with full-length GADD34 as bait in order to identify additional protein partners of GADD34. We report here that human cochaperone protein BAG-1 interacts with GADD34 in vitro and in SW480 cells treated with the proteasome inhibitor z-LLL-B to induce apoptosis. Two other proteins, Hsp70/Hsc70 and PP1, associate reversibly with the GADD34-BAG-1 complex, and their dissociation is promoted by ATP. BAG-1 negatively modulates GADD34-bound PP1 activity, and the expression of BAG-1 isoforms can also mask GADD34-mediated inhibition of colony formation and suppression of transcription. Our findings suggest that BAG-1 may function to suppress the GADD34-mediated cellular stress response and support a role for BAG-1 in the survival of cells undergoing stress.
Hung
Wesley J
WJ
Division of Medical Oncology, Department of Medicine, Veterans Administration Puget Sound Health Care System, Seattle Division, 1660 S. Columbian Way, Seattle, WA 98108, USA.
Roberson
Rachel S
RS
Taft
Jaime
J
Wu
Daniel Y
DY
D016475:3T3 Cells; D000818:Animals; D000943:Antigens, Differentiation; D017209:Apoptosis; D002352:Carrier Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins; D002460:Cell Line; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D005434:Flow Cytometry; D005982:Glutathione Transferase / Q000378:metabolism; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D051379:Mice; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D020033:Protein Isoforms; D054645:Protein Phosphatase 1; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism*; D000071796:SMARCB1 Protein; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D020798:Two-Hybrid System Techniques
D000943:Antigens, Differentiation; C091732:BCL2-associated athanogene 1 protein; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D015852:Eukaryotic Initiation Factor-2; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C494371:HSPA8 protein, human; C494372:Hspa8 protein, mouse; D020033:Protein Isoforms; D011506:Proteins; D000071796:SMARCB1 Protein; C513266:SMARCB1 protein, human; C513265:Smarcb1 protein, mouse; D014157:Transcription Factors; D005982:Glutathione Transferase; C087519:PPP1R15A protein, human; C513256:Ppp1r15a protein, mouse; D054645:Protein Phosphatase 1