While a relatively limited number of known oncogenes underlie a large percentage of cancers, a variety of new genes have emerged as low-frequency cancer drivers. Each of these new oncogenes represents a frontier for targeted therapy. However, the discovery of low-frequency targetable oncogenic drivers is challenging. This study focuses on the poorly understood Tyrosine kinase non-receptor-1 (TNK1), which has been reported to have both oncogenic and tumor suppressive functions. TNK1 has been identified to promote cancer cells survival and promote chemoresistance in multiple independent studies. On the other hand, whole-body constitutive deletion of TNK1 in mice caused an increase in spontaneous carcinomas and lymphomas. All in all, with no known regulatory mechanism and substrates of TNK1, the precise biological role of TNK1 is still unclear. To understand how TNK1 is regulated, we employed a proteomic approach to identify TNK1 interactors. We found out that TNK1 interacts with the phospho-binding protein 14-3-3 and this interaction is mediated by a cluster of MARK-mediated phosphorylations within the proline-rich domain. 14-3-3 binding retains TNK1 in the cytosol and maintains TNK1 in an inactive state. Release of TNK1 from 14-3-3 binding drives TNK1 to a heavy membrane fraction, where it becomes highly active. One unique feature of TNK1 is an ubiquitin association domain (UBA) on its C-terminus. Our data suggest that the UBA domain of TNK1 binds to poly-ubiquitin chains in nondiscriminatory manner. Remarkably, point mutations within the UBA that disrupt ubiquitin binding abolish TNK1 activation and oncogenic signaling, suggesting, to our knowledge, a unique UBA-centric mechanism of tyrosine kinase regulation. Finally, we used a structure-guided approach to identify a small molecule inhibiting TNK1 with high potency and selectivity. Such compound, TP-5801, inhibits TNK1 dependent STAT3 phosphorylation. TP-5801 also prolongs the survival of mice injected via tail vein with TNK1-driven Ba/F3 cells and reduces tumor burden in a subcutaneous xenograft model. In conclusion, our data reveal a mechanism of TNK1 regulation that controls its oncogenic tyrosine kinase activity and a potential strategy for TNK1 inhibition.
College and Department
Physical and Mathematical Sciences; Chemistry and Biochemistry
BYU ScholarsArchive Citation
Chan, Tsz Yin, "Discovery of a Novel Regulatory Mechanism of TNK1 by 14-3-3 and Its Ubiquitin Association Domain Provides a Potential Therapeutic Targeting Opportunity in Cancer" (2020). Theses and Dissertations. 9252.
tyrosine kinase, TNK1, 14-3-3, Ubiquitin association domain, UBA, MARK, STAT3