The CUL5 ubiquitin ligase complex mediates resistance to CDK9 and MCL1 inhibitors in lung cancer cells
- University of California, Berkeley, United States
- AstraZeneca, United States
Abstract
Overexpression of anti-apoptotic proteins MCL1 and Bcl-xL are frequently observed in many cancers. Inhibitors targeting MCL1 are in clinical development, however numerous cancer models are intrinsically resistant to this approach. To discover mechanisms underlying resistance to MCL1 inhibition, we performed multiple flow-cytometry based genome-wide CRISPR screens interrogating two drugs that directly (MCL1i) or indirectly (CDK9i) target MCL1. Remarkably, both screens identified three components (CUL5, RNF7 and UBE2F) of a cullin-RING ubiquitin ligase complex (CRL5) that resensitized cells to MCL1 inhibition. We find that levels of the BH3-only pro-apoptotic proteins Bim and Noxa are proteasomally regulated by the CRL5 complex. Accumulation of Noxa caused by depletion of CRL5 components was responsible for re-sensitization to CDK9 inhibitor, but not MCL1 inhibitor. Discovery of a novel role of CRL5 in apoptosis and resistance to multiple types of anti-cancer agents suggests the potential to improve combination treatments.
Data availability
Sequencing data is being deposited into SRA under accession code: SUB5033643
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Genome-wide CRISPRi Resensitization Screens with MCL1 InhibitorsNCBI Sequence Read Archive, SUB5033643.
Article and author information
Author details
Funding
AstraZeneca
- Shaheen Kabir
- Justin Cidado
- Courtney Andersen
- Cortni Dick
- Pei-Chun Lin
- Hong Ma
- Matthew A Belmonte
- Lisa Drew
- Jacob E Corn
National Institutes of Health (DP2 HL141006)
- Jacob E Corn
Li Ka Shing Foundation
- Jacob E Corn
Heritage Medical Research Institute
- Jacob E Corn
California Institute for Regenerative Medicine (DISC1-08776)
- Shaheen Kabir
- Seung Hyun Baik
- Jacob E Corn
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Michael R Green, Howard Hughes Medical Institute, University of Massachusetts Medical School, United States
Version history
- Received: December 15, 2018
- Accepted: July 5, 2019
- Accepted Manuscript published: July 11, 2019 (version 1)
- Version of Record published: August 20, 2019 (version 2)
- Version of Record updated: October 7, 2019 (version 3)
Copyright
© 2019, Kabir et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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The CUL5 ubiquitin ligase complex mediates resistance to CDK9 and MCL1 inhibitors in lung cancer cells
eLife 8:e44288.
https://doi.org/10.7554/eLife.44288
Further reading
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Abelson tyrosine kinase (Abl) is regulated by the arrangement of its regulatory core, consisting sequentially of the SH3, SH2, and kinase (KD) domains, where an assembled or disassembled core corresponds to low or high kinase activity, respectively. It was recently established that binding of type II ATP site inhibitors, such as imatinib, generates a force from the KD N-lobe onto the SH3 domain and in consequence disassembles the core. Here, we demonstrate that the C-terminal αI-helix exerts an additional force toward the SH2 domain, which correlates both with kinase activity and type II inhibitor-induced disassembly. The αI-helix mutation E528K, which is responsible for the ABL1 malformation syndrome, strongly activates Abl by breaking a salt bridge with the KD C-lobe and thereby increasing the force onto the SH2 domain. In contrast, the allosteric inhibitor asciminib strongly reduces Abl’s activity by fixating the αI-helix and reducing the force onto the SH2 domain. These observations are explained by a simple mechanical model of Abl activation involving forces from the KD N-lobe and the αI-helix onto the KD/SH2SH3 interface.
