title: Targeting of Miz-1 is essential for Myc-mediated apoptosis.
abstract: The c-Myc oncoprotein plays a central role in human cancer via its ability to either activate or repress the transcription of essential downstream targets. For many of the repressed target genes, down-regulation by c-Myc relies on its ability to bind and inactivate the transcription factor Miz-1. Although Miz-1 inactivation is suspected to be essential for at least some of the biological activities of c-Myc, it has been difficult to demonstrate this requirement experimentally. Using a combination of short hairpin RNA-mediated knockdown and a previously characterized mutant of c-Myc that is defective for Miz-1 inactivation, we examined whether this inactivation is critical for three of the most central biological functions of c-Myc, cell cycle progression, transformation, and apoptosis. The results of this analysis demonstrated that in the in vitro assays utilized here, Miz-1 inactivation is dispensable for c-Myc-induced cell cycle progression and transformation. In marked contrast, the ability of c-Myc to induce apoptosis in primary diploid human fibroblasts in response to growth factor withdrawal is entirely dependent on its ability to inactivate Miz-1. These data have a significant impact on our understanding of the biochemical mechanisms dictating how c-Myc mediates opposing biological functions, such as transformation and apoptosis, and demonstrate the first requirement for Miz-1 inactivation in any of the biological functions of c-Myc.
authors.affiliation: The Wistar Institute, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Jagruti H
authors.initials: JH
authors.lastname: Patel
authors.forename: Steven B
authors.initials: SB
authors.lastname: McMahon
mesh_terms: D000362:Agar / Q000737:chemistry; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002453:Cell Cycle; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015536:Down-Regulation; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D051741:Kruppel-Like Transcription Factors; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D012313:RNA / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D012190:Retroviridae / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; D051741:Kruppel-Like Transcription Factors; D016271:Proto-Oncogene Proteins c-myc; D014157:Transcription Factors; C107961:ZBTB17 protein, human; D012313:RNA; D000362:Agar