Proteasomal degradation of the tumour suppressor FBW7 requires branched ubiquitylation by TRIP12

Omar M Khan; Jorge Almagro; Jessica K Nelson; Stuart Horswell; Vesela Encheva; Kripa S Keyan; Bruce E Clurman; Ambrosius P Snijders; Axel Behrens

doi:10.1038/s41467-021-22319-5

Proteasomal degradation of the tumour suppressor FBW7 requires branched ubiquitylation by TRIP12

Nat Commun. 2021 Apr 6;12(1):2043. doi: 10.1038/s41467-021-22319-5.

Authors

Omar M Khan^{1

2}, Jorge Almagro^#³, Jessica K Nelson^#³, Stuart Horswell⁴, Vesela Encheva⁵, Kripa S Keyan⁶, Bruce E Clurman⁷, Ambrosius P Snijders⁵, Axel Behrens^{8

9

10

11}

Affiliations

¹ Adult Stem Cell Laboratory, The Francis Crick Institute, London, UK. okhan@hbku.edu.qa.
² Hamad Bin Khalifa University, College of Health and Life Sciences Qatar Foundation, Education City, Education City, Doha, Qatar. okhan@hbku.edu.qa.
³ Adult Stem Cell Laboratory, The Francis Crick Institute, London, UK.
⁴ Bioinformatics and Biostatistics, London, UK.
⁵ Proteomics, The Francis Crick Institute, London, UK.
⁶ Hamad Bin Khalifa University, College of Health and Life Sciences Qatar Foundation, Education City, Education City, Doha, Qatar.
⁷ Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
⁸ Adult Stem Cell Laboratory, The Francis Crick Institute, London, UK. axel.behrens@icr.ac.uk.
⁹ Cancer Stem Cell Laboratory, Institute of Cancer Research, London, UK. axel.behrens@icr.ac.uk.
¹⁰ Division of Cancer, Department of Surgery and Cancer, Imperial College London, London, UK. axel.behrens@icr.ac.uk.
¹¹ Convergence Science Centre, Imperial College London, London, UK. axel.behrens@icr.ac.uk.

^# Contributed equally.

Abstract

The tumour suppressor FBW7 is a substrate adaptor for the E3 ubiquitin ligase complex SKP1-CUL1-F-box (SCF), that targets several oncoproteins for proteasomal degradation. FBW7 is widely mutated and FBW7 protein levels are commonly downregulated in cancer. Here, using an shRNA library screen, we identify the HECT-domain E3 ubiquitin ligase TRIP12 as a negative regulator of FBW7 stability. We find that SCF^FBW7-mediated ubiquitylation of FBW7 occurs preferentially on K404 and K412, but is not sufficient for its proteasomal degradation, and in addition requires TRIP12-mediated branched K11-linked ubiquitylation. TRIP12 inactivation causes FBW7 protein accumulation and increased proteasomal degradation of the SCF^FBW7 substrate Myeloid Leukemia 1 (MCL1), and sensitizes cancer cells to anti-tubulin chemotherapy. Concomitant FBW7 inactivation rescues the effects of TRIP12 deficiency, confirming FBW7 as an essential mediator of TRIP12 function. This work reveals an unexpected complexity of FBW7 ubiquitylation, and highlights branched ubiquitylation as an important signalling mechanism regulating protein stability.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Biocatalysis
Carrier Proteins / metabolism*
Drug Resistance, Neoplasm
F-Box-WD Repeat-Containing Protein 7 / metabolism*
HCT116 Cells
HEK293 Cells
Humans
Lysine / metabolism
Myeloid Cell Leukemia Sequence 1 Protein / metabolism
Proteasome Endopeptidase Complex / metabolism*
Protein Binding
Protein Processing, Post-Translational
Protein Stability
Proteolysis*
RNA, Small Interfering / metabolism
Substrate Specificity
Ubiquitin-Conjugating Enzymes / metabolism
Ubiquitin-Protein Ligases / metabolism*
Ubiquitination*

Substances

Carrier Proteins
F-Box-WD Repeat-Containing Protein 7
MCL1 protein, human
Myeloid Cell Leukemia Sequence 1 Protein
RNA, Small Interfering
Ube2S protein, human
Ubiquitin-Conjugating Enzymes
TRIP12 protein, human
Ubiquitin-Protein Ligases
Proteasome Endopeptidase Complex
Lysine

Abstract

Publication types

MeSH terms

Substances

Grants and funding