Abstract

Prostate tumor overexpressed 1 (PTOV1) is highly expressed in several forms of cancer. High expression of PTOV1 is associated with tumor aggressiveness in several tumor types, including ovarian and breast cancer. Currently, PTOV1 is known to act both as a translational and transcriptional regulator aiding in the expression of prosurvival genes. Although PTOV1 is known to pass in and out of the nucleus in a cell cycle-dependent manner, the regulation of PTOV1 activity is not well understood and here we identify 14-3-3 as a PTOV1 interactor and show that high levels of 14-3-3 expression, like PTOV1, correlate with prostate cancer progression. Further, we identify SGK2-mediated phosphorylation at S36 of PTOV1 that is required for 14-3-3 binding. Disruption of the PTOV1-14-3-3 interaction results in an accumulation of PTOV1 in the nucleus and a proteasome-dependent reduction in PTOV1 protein levels, which requires ubiquitination at K114 of PTOV1. We also observed HUWE1 as a PTOV1-interacting partner responsible for the degradation of PTOV1 through the proteasome. We show that loss of 14-3-3 binding leads to an increase in PTOV1-HUWE1 binding, suggesting that 14-3-3 stabilizes PTOV1 protein by sequestering PTOV1 in the cytosol and inhibiting its interaction with HUWE1. Finally, our data suggest that stabilization of the 14-3-3-bound form of PTOV1 promotes PTOV1-mediated expression of cJun. Together, these data support a model that explains how 14-3-3 and HUWE1 regulate the PTOV1 stability, localization, and function within the cell.

Degree

College and Department

Physical and Mathematical Sciences; Chemistry and Biochemistry

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