CHIP ubiquitylates NOXA and induces its lysosomal degradation in response to DNA damage

Marie-Christine Albert,Kerstin Brinkmann,Thorsten Hoppe,Saskia Diana Günther,Hamid Kashkar,Wojciech Pokrzywa,Martin Krönke

doi:10.1038/s41419-020-02923-x

Abstract

The BH3-only protein NOXA is a regulator of mitochondrial apoptosis by specifically antagonizing the anti-apoptotic protein MCL-1. Here we show that the E3 ubiquitin ligase CHIP controls NOXA stability after DNA damage. Our findings reveal that CHIP and MCL-1 are binding partners of NOXA and differentially define the fate of NOXA. Whereas NOXA is initially targeted to mitochondria upon MCL-1-binding, CHIP mediates ubiquitylation of cytosolic NOXA and promotes lysosomal degradation of NOXA, which is not bound by MCL-1. Our data indicate that MCL-1 defines NOXA abundance and its pro-apoptotic activity. Increased NOXA levels beyond this threshold are effectively removed by lysosomal protein degradation triggered via CHIP-mediated ubiquitylation. Together, these results shed new light on regulatory circuits controlling DNA damage response and identified the E3 ligase CHIP as a new molecular guardian, which restricts the cytosolic accumulation of NOXA upon genotoxic stress.

Highlights

Introduction TheBH3-only protein NOXA is a p53-responsive gene involved in mitochondrial apoptosis triggered by DNA damage[1]
Our data show that both NOXA transcript and protein levels are elevated in response to genotoxic stress induced by the anthracycline drug doxorubicin (DOX) in a dose- and time-dependent manner (Fig. 1a and Supplementary Fig. S1A)
In addition to the calculated molecular mass of NOXA protein (~10 kDa), immunoprecipitation with NOXA-specific antibody revealed an accumulation of higher molecular weight forms of NOXA, suggesting that NOXA protein is modified in response to DNA damage (Fig. 1a)

Summary

Introduction

Introduction TheBH3-only protein NOXA is a p53-responsive gene involved in mitochondrial apoptosis triggered by DNA damage[1]. NOXA is critical in apoptosis due to its distinct capability to bind and antagonize MCL-1 (myeloid leukemia cell 1) an anti-apoptotic member of the BCL-2 protein family[2,3,4,5]. The use of proteasome inhibitors in tumor cells has been frequently associated with the accumulation of NOXA at the protein level, which in turn potentiates susceptibility towards cancer therapeutics by antagonizing MCL-19,13–15. MARCH5 is a component of mitochondrial quality control, which requires the mitochondrial outer membrane protein MTCH2 to mark MCL-1 for proteasomal degradation This can only occur when MCL-1 is bound by NOXA and results in the Official journal of the Cell Death Differentiation Association

Methods

Results

Conclusion