title: In vivo quantification and perturbation of Myc-Max interactions and the impact on oncogenic potential.
abstract: The oncogenic bHLH-LZ transcription factor Myc forms binary complexes with its binding partner Max. These and other bHLH-LZ-based protein-protein interactions (PPI) in the Myc-Max network are essential for the physiological and oncogenic activities of Myc. We have generated a genetically determined and highly specific protein-fragment complementation assay based on Renilla luciferase to analyze the dynamic interplay of bHLH-LZ transcription factors Myc, Max, and Mxd1 in vivo. We also applied this PPI reporter to quantify alterations of nuclear Myc-Max complexes in response to mutational events, competitive binding by the transcriptional repressor Mxd1, or perturbations by small-molecule Myc inhibitors, including recently identified potent PPI inhibitors from a Kröhnke pyridine library. We show that the specificity of Myc-Max PPI reduction by the pyridine inhibitors directly correlates with their efficient and highly specific potential to interfere with the proliferation of human and avian tumor cells displaying deregulated Myc expression. In a direct comparison with known Myc inhibitors using human and avian cell systems, the pyridine compounds reveal a unique inhibitory potential even at sub-micromolar concentrations combined with remarkable specificity for the inhibition of Myc-driven tumor cell proliferation. Furthermore, we show in direct comparisons using defined avian cell systems that different Max PPI profiles for the variant members of the Myc protein family (c-Myc, v-Myc, N-Myc, L-Myc) correlate with their diverse oncogenic potential and their variable sensitivity to the novel pyridine inhibitors.
authors.affiliation: Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Raffeiner
authors.affiliation: Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria.
authors.forename: Ruth
authors.initials: R
authors.lastname: Röck
authors.affiliation: Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria.
authors.forename: Andrea
authors.initials: A
authors.lastname: Schraffl
authors.affiliation: Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria.
authors.forename: Markus
authors.initials: M
authors.lastname: Hartl
authors.affiliation: Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA.
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Hart
authors.affiliation: Department of Chemistry, The Scripps Research Institute, La Jolla, CA.
authors.forename: Kim D
authors.initials: KD
authors.lastname: Janda
authors.affiliation: Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA.
authors.forename: Peter K
authors.initials: PK
authors.lastname: Vogt
authors.affiliation: Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria.
authors.forename: Eduard
authors.initials: E
authors.lastname: Stefan
authors.affiliation: Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria.
authors.forename: Klaus
authors.initials: K
authors.lastname: Bister
mesh_terms: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D049410:Luciferases, Renilla; D009369:Neoplasms / Q000378:metabolism; D010069:Oxadiazoles / Q000494:pharmacology; D011485:Protein Binding; D055503:Protein Multimerization; D016271:Proto-Oncogene Proteins c-myc / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D012097:Repressor Proteins / Q000378:metabolism*; D013844:Thiazoles / Q000494:pharmacology
chemical_list: C534883:10074-G5; C524814:5-(4-ethylbenzylidene)-2-thioxothiazolidin-4-one; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; C000593138:KJ-Pyr-9; C106465:MNT protein, human; C079439:MXD1 protein, human; D010069:Oxadiazoles; D016271:Proto-Oncogene Proteins c-myc; D011725:Pyridines; D012097:Repressor Proteins; D013844:Thiazoles; D049410:Luciferases, Renilla