title: Nutlin-3 induces BCL2A1 expression by activating ELK1 through the mitochondrial p53-ROS-ERK1/2 pathway.
abstract: Nutlin-3 which occupies the p53 binding pocket in HDM2, has been reported to activate apoptosis through both the transcriptional activity-dependent and -independent programs of p53. Transcription-independent apoptosis by nutlin-3 is triggered by p53 which is translocated to mitochondria. However, we previously demonstrated that the nutlin-3-induced mitochondrial translocation of p53 stimulates ERK1/2 activation, an anti-apoptosis signal, via mitochondrial ROS generation. We report on how nutlin-3-stimulated ERK1/2 activity inhibits p53-induced apoptosis. Among the anti-apoptotic BCL2 family proteins, BCL2A1 expression was increased by nutlin-3 at both the mRNA and protein levels, and this increase was prevented by the inhibition of ERK1/2. TEMPO, a ROS scavenger, and PFT-μ , a blocker of the mitochondrial translocation of p53, also inhibited BCL2A1 expression as well as ERK1/2 phosphorylation. In addition, nutlin-3 stimulated phosphorylation of ELK1, which was prevented by all compounds that inhibited nutlin-3-induced ERK1/2 such as U0126, PFT-μ and TEMPO. Moreover, an increase in BCL2A1 expression was weakened by the knockdown of ELK1. Finally, nutlin-3-induced apoptosis was found to be potentiated by the knockdown of BCL2A1, as demonstrated by an increase of in hypo-diploidic cells and Annexin V-positive cells. Parallel to the increase in apoptotic cells, the knockdown of BCL2A1 augmented the cleavage of poly(ADP-ribose) polymerase-1. It is noteworthy that the augmented levels of apoptosis induced by the knockdown of BCL2A1 were comparable to those of apoptosis induced by U0126. Collectively, these results suggest that nutlin-3-activated ERK1/2 may stimulate the transcription of BCL2A1 via the activation of ELK1, and BCL2A1 expression may contribute to the inhibitory effect of ERK1/2 on nutlin-3-induced apoptosis, thereby constituting a negative feedback loop of p53-induced apoptosis.
authors.affiliation: Department of Biochemistry, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea.
authors.forename: Sun-Young
authors.initials: SY
authors.lastname: Lee
authors.affiliation: Department of Biochemistry, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea.
authors.forename: Hyun Chul
authors.initials: HC
authors.lastname: Choi
authors.affiliation: Department of Biochemistry, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea.
authors.forename: Yun-Jeong
authors.initials: YJ
authors.lastname: Choe
authors.affiliation: Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea.
authors.forename: Seok Joon
authors.initials: SJ
authors.lastname: Shin
authors.affiliation: Cancer Evolution Research Center, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea.
authors.forename: Sug Hyung
authors.initials: SH
authors.lastname: Lee
authors.affiliation: Department of Biochemistry, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea.
authors.forename: Ho-Shik
authors.initials: HS
authors.lastname: Kim
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000187:drug effects; D005434:Flow Cytometry; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D015151:Immunoblotting; D020935:MAP Kinase Signaling System / Q000502:physiology; D015778:Minor Histocompatibility Antigens; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D012516:Osteosarcoma / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis*; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D050807:ets-Domain Protein Elk-1 / Q000378:metabolism*
chemical_list: C096816:BCL2-related protein A1; C494112:ELK1 protein, human; D007093:Imidazoles; D015778:Minor Histocompatibility Antigens; D010879:Piperazines; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D050807:ets-Domain Protein Elk-1; C482205:nutlin 3