Order-disorder transitions in cancer-related proteins

Intrinsically disordered proteins (IDPs) lack a stable secondary and tertiary structure, making them highly flexible and dynamic. The flexibility provides a challenge for finding drugs that target intrinsically disordered proteins through a structure-based approach. IDPs play a crucial role in the rise of many cancers, over 65% of all cancer- related proteins are intrinsically disordered.

In paper I, we studied the transactivation domains TAD1 and TAD2 of tumor suppressor p53, which is known for extremely low expression levels and poor conformational stability. As a result of these limitations, p53 is a difficult target for therapeutics development. We investigated whether these characteristics can be altered through fusion of p53 to a highly soluble spider silk domain termed NT *. The chimeric protein shows efficient translation and exhibits increased activity in cells. Biophysical characterization of NT*p53 revealed a more compact conformation of the transactivation domains, which are wrapped around the spider silk protein domain. The interactions between NT* and the disordered p53 N-terminus increase translation efficiency and unblocks translation in vitro.

In paper II, we changed our focus from p53 to c-MYC. We used a reductionist approach to characterize the local dynamics and structural heterogeneity of c-MYC. Using molecular dynamics simulations and machine learning, we identified a conformational switch in the transactivation domain of c-MYC, which we later defined as coreMYC, that alternates between a compact, inactive and an extended, active conformational state. Use of epigallocatechin gallate (EGCG) allows compaction of coreMYC and promotion of the inactive state. We show the effect of EGCG on both coreMYC and full-length c-MYC through a selection of biophysical and cellular assays. We find that the induction of a compact conformation of coreMYC inhibits its interactions with binding partners that are essential for transcriptional and oncogenic activity of c-MYC. Our study provides insight in the structure-activity relationship of c- MYC and identifies a potential target for therapeutic intervention.

In paper III, we investigate the structural features of MYC-box II and its role in ligand binding. To do so, we used a selection of techniques, including NMR, molecular dynamics simulations and native mass spectrometry. We found that specific functional groups such as a positive charge and an aromatic ring will drive ligand binding to a highly conserved DCMW motif at the center of MBII, while hydrophilic groups will interact with the transient helices that surround the DCMW motif. The results indicate how we can select specific small molecules with predetermined functional group that can target MBII in a more specific way.

List of scientific papers

I. Kaldmäe Margit, Vosselman Thibault, Zhong Xueying, Lama Dilraj, Chen Gefei, Saluri Mihkel, Kronqvist Nina, Siau Jia Wei, Ng Aik Seng, Ghadessy Farid J, Sabatier Pierre, Vojtesek Borivoj, Sarr Medoune, Sahin Cagla, Osterlund Nicklas, Leopold L Llag, Väänänen Venla A, Sedimbi Saikiran, Arsenian-Henriksson Marie, Zubarev Roman A, Nilsson Lennart, Koeck Philip J B, Rising Anna, Abelein Axel, Fritz Nicolas, Johansson Jan, Lane David P, Landreh Michael. A "spindle and thread" mechanism unblocks p53 translation by modulating N-terminal disorder. Structure, 2022 May 5;30(5):733-742.e7. https://doi.org/10.1016/j.str.2022.02.013

II. Lama Dilraj*, Vosselman Thibault, Sahin Cagla, Liaño-Pons Judit, Cerrato Carmine P, Nilsson Lennart, Teilum Kaare, Lane David P, Landreh Michael, Arsenian Henriksson Marie. A druggable conformational switch in the c-MYC transactivation domain. Nat Commun., 2024 Feb 29;15(1):1865. https://doi.org/10.1038/s41467-024-45826-7

* Equal Contribution

III. Vosselman Thibault, Sahin Cagla, Lane David P, Teilum Kaare, Arsenian Henriksson Marie, Landreh Michael and Lama Dilraj. Specific targeting of MYC-box II using small molecules. [Manuscript]