Aurora A binds to the transactivation domain of c-Myc and recognizes the phosphorylated N-terminal degron motif.

Abstract

The oncoprotein c-Myc is overexpressed or mutated in a large fraction of human cancers. The stability of c-Myc is controlled by phosphorylation of T58 and S62 within a conserved degron motif in the N-terminal transactivation domain, which triggers recruitment of the SCF ubiquitin ligase. The kinase Aurora A (AurA) has been shown to bind to both c-Myc and its paralog N-Myc and to promote their stability by interfering with ubiquitination and degradation. Here we show, using NMR and FRET experiments, that AurA binds to c-Myc through several discrete interactions spanning 145 residues within its transactivation domain. AurA binding to c-Myc is enhanced by phosphorylation of the T58/S62 degron, demonstrating that the kinase recognizes the pool of c-Myc that has been marked for degradation by the ubiquitin proteasome pathway. Although AurA binds to segments of c-Myc flanking the degron, it does not appear to form extensive interactions with the phosphorylated degron itself, potentially leaving it accessible on the AurA surface. These observations establish a foundation for understanding the role of AurA in regulating c-Myc ubiquitination and degradation.