Book/Dissertation / PhD Thesis

DKFZ-2023-02596

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Characterization of novel substrates of SCF-FBXW7 in mitotic cell fate regulation

Hänle-Kreidler, S.DKFZ*

2023
--- Heidelberg
ISBN: not applicable

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Abstract: Protein ubiquitylation is a post-translational modification, which can control various cellular processes. Ubiquitin is conjugated to a substrate by an enzymatic cascade comprising so-called ubiquitin writers: E1, E2 and E3 enzymes. More of the ubiquitin-code is continuously uncovered and functional relationships are established. The induction of proteasomal degradation is probably the most prominent function of protein ubiquitylation. The E3 ubiquitin ligases convey specificity by facilitating the substrate interaction. SKP1-CUL1-F-box protein complexes belong to the RING E3 ubiquitin ligases and are one of the largest groups of the over 600 human E3 ubiquitin ligases. Their substrate receptors, the F-box proteins, are interchangeable and they can therefore target a vast number of substrates. FBXW7 is one of the best characterized F-box proteins and acts as a tumor suppressor by targeting oncogenes like c-Myc, Cyclin E1 and NOTCH1 for degradation. Being the most frequently mutated F-box protein in human cancers, FBXW7 loss-of-function or deletion result in increased tumor proliferation and chemoresistance. FBXW7-deficiency promotes mitotic slippage in response to antimicrotubule drugs and the identification of FBXW7 substrates responsible for this phenotype remains a major task.In the presented thesis, I aimed at identifying novel substrates of FBXW7 which are involved in mitotic slippage to better understand mitotic cell fate regulation. Using a proteomics approach, I identified the Histone 3 lysine 4 methyltransferase complex component WDR5 as FBXW7 candidate substrates and showed that FBXW7 regulates WDR5 protein levels by ubiquitylation. I verified that FBXW7 and WDR5 interact in-vivo and in-vitro and found that the overexpression of WDR5 and Cyclin E1 can promote mitotic slippage. Reciprocally, the depletion of WDR5 and Cyclin E1 reduced mitotic slippage induced by knockdown of FBXW7 and significantly reduced polyploidization after mitotic slippage. Although the methyltransferase enzymatic subunit KMT2D is a substrate of FBXW7 and cooperates with WDR5, knockdown of KMT2D did not affect mitotic cell fate.Collectively, I identified WDR5 as a novel substrate of FBXW7 and showed that the FBXW7 substrates WDR5 and Cyclin E1 can promote mitotic slippage and are required for drug-induced polyploidy. My results help to better understand the mechanisms underlying chemotherapy resistance caused by treatment of cancers with antimicrotubule drugs.

Note: not applicable
Note: Dissertation, Universität Heidelberg, 2023

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Contributing Institute(s):

1. F045 Zellzykluskontrolle und Carcinogenese (F045)

Research Program(s):

1. 316 - Infektionen, Entzündung und Krebs (POF4-316) (POF4-316)

Appears in the scientific report 2023

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