Stress-induced activation of p53 is an essential cellular response to prevent aberrant cell proliferation and cancer development. The ubiquitin ligase MDM2 promotes p53 degradation and limits the duration of p53 activation. It remains unclear, however, how p53 persistently escapes MDM2-mediated negative control for making appropriate cell fate decisions. Here we report that TBP-like protein (TLP), a member of the TBP family, is a new regulatory factor for the p53-MDM2 interplay and thus for p53 activation. We found that TLP acts to stabilize p53 protein to ensure long-lasting p53 activation, leading to potentiation of p53-induced apoptosis and senescence after genotoxic stress. Mechanistically, TLP interferes with MDM2 binding and ubiquitination of p53. Moreover, single cell imaging analysis shows that TLP depletion accelerates MDM2-mediated nuclear export of p53. We further show that a cervical cancer-derived TLP mutant has less p53 binding ability and lacks a proliferation-repressive function. Our findings uncover a role of TLP as a competitive MDM2 blocker, proposing a novel mechanism by which p53 escapes the p53-MDM2 negative feedback loop to modulate cell fate decisions.
Keywords: cancer; cell growth; p53; protein stability; transcription factor.
© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.