Structural biology of transcriptional regulation in the c-Myc network

Abstract: The oncogene c-­?Myc is overexpressed in many types of human cancers and regulation of c-­?Myc expression is crucial in a normal cell. The intrinsically disordered N-­?terminal transactivation domain interacts with a wide range of proteins regulating c-­?Myc activity. The highly conserved Myc box I region includes residues Thr58 and Ser62, which are involved in the phosphorylation events that control c-­?Myc degradation by ubiquitination. Aggressive cell growth, leading to tumor formation, occurs if activated c-­? Myc is not degraded by ubiquitination. Such events may be triggered by defects in the regulated network of interactions involving Pin1 and phospho-­?dependent kinases.In this thesis, the properties of the intrinsically disordered unphosphorylated c-­?Myc1-­?88 and its interaction with Bin1 are studied by nuclear magnetic resonance (NMR) spectroscopy and surface plasmon resonance (SPR). Furthermore, the interaction of Myc1-­?88 with Pin1 is analyzed in molecular detail, both for unphosphorylated and Ser62 phosphorylated c-­?Myc1-­?88, providing a first molecular description of a disordered but specific c-­?Myc complex. A detailed analysis of the dynamics and structural properties of the transcriptional activator TAF in complex with TBP, both by NMR spectroscopy and crystallography, provides insight into transcriptional regulation and how c-­?Myc could interact with TBP. Finally, the structure of a novel N-­?terminal domain motif in FKBP25, which we name the Basic Tilted Helix Bundle (BTHB) domain, and its binding to YY1, which also binds c-­?Myc, is described. By investigating the structural and dynamic properties of c-­?Myc and c-­?Myc-­?interacting proteins, this thesis thus provides further insight to the molecular basis for c-­?Myc functionality in transcriptional regulation.