Biology subjects

Claridge, J. K.

Publications and source records attributed to Claridge, J. K..

3 recordsLinked to original sources

bioRxiv2023

Menin regulates androgen receptor- and MLL-driven condensation, upsetting regulation of cellular AR-driven transcription.

Menin is a protein that is regulated via protein-protein interactions by different binding partners, such as mixed lineage leukemia protein (MLL) and androgen receptor (AR). We observed that menin-AR and menin-MLL interactions are regulated by concentration-dependent dimerization of menin, and its interaction with cancer-related AR. As a result of its oligomerization-dependent interaction with both AR and MLL, menin is recruited into AR-RNA and MLL-RNA condensates formed by liquid-liquid phase separation (LLPS), with different outcomes under AR-overexpression or MLL-overexpression conditions representing different cancer types. At high concentrations promoting menin dimerization, it inhibits MLL-RNA LLPS, while making AR-RNA condensates less dynamic, i.e., more gel-like. Regions of AR show both negative/positive cooperativity in menin binding. AR contains a specific menin-binding region (MBR) in its intrinsically disordered N-terminal domain (NTD), menin binding of which is inhibited by the adjacent DNA-binding domain (DBD), but facilitated by a hinge region located between its DBD and ligand-binding domain (LBD) as well as by N terminus of AR. Interestingly, the hinge region reduces the propensity of full-length AR to undergo LLPS in the presence of RNA, which is facilitated by an alternative hinge region present in the tumor-specific AR isoform, AR-v7. As both menin and MLL are recruited into AR-driven, functional cellular condensates aggravated in the case of AR-v7, we posit that the menin-AR-MLL system represents a fine-tuned condensate module of transcription regulation that is balanced toward the tumor-suppressor activity of menin. Our results suggest that this balance can be upset by prevalent oncogenic events, such as menin upregulation and/or AR-v7 overexpression, in cancer.

biochemistry↗

bioRxiv2023

The folding-limited nucleation of curli hints at an evolved safety mechanism for functional amyloid production

It is nearly two decades ago that the thin aggregative fimbriae which had been shown to enhance the biofilm formation of Salmonella enteriditis and Escherichia coli were identified as amyloid fibers. The realization that natural proteins can develop amyloidogenic traits as part of their functional repertoire instigated a search for similar proteins across all kingdoms of life. That pursuit has since unearthed dozens of candidates which now constitute the family of proteins referred to as functional amyloids (FA). FAs are promising candidates for future synthetic biology applications in that they marry the structural benefits of the amyloid fold (self-assembly and stability) while steering clear of the cytotoxicity issues that are typically linked to amyloid associated human pathologies. Unfortunately, the extreme aggregation propensity of FAs and the associated operational difficulties are restricting their adoption in real-world applications, underscoring the need for additional processes to control the amyloid reaction. Here we untangle the molecular mechanism of amyloid formation of the canonical functional amyloid curli using NMR, native mass spectrometry and cryo-electron microscopy. Our results are consistent with folding-limited one-step amyloid nucleation that has emerged as an evolutionary balance between efficient extracellular polymerization, while steering clear of pre-emptive nucleation in the periplasm. Sequence analysis of the amyloid curlin kernel suggests a finetuning of the rate of monomer folding via modulation of the secondary structure propensity of the pre-amyloid species, opening new potential avenues towards control of the amyloid reaction.

biochemistry↗

bioRxiv2019

Site-directed M2 proton channel inhibitors enable synergistic combination therapy for rimantadine-resistant pandemic influenza

Pandemic influenza A virus (IAV) remains a significant threat to global health. Preparedness relies primarily upon a single class of neuraminidase (NA) targeted antivirals, against which resistance is steadily growing. The M2 proton channel is an alternative clinically proven antiviral target, yet a near-ubiquitous S31N polymorphism in M2 evokes resistance to licensed adamantane drugs. Hence, inhibitors capable of targeting N31 containing M2 (M2-N31) are highly desirable.\n\nRational in silico design and in vitro screens delineated compounds favouring either lumenal or peripheral M2 binding, yielding effective M2-N31 inhibitors in both cases. Hits included adamantanes as well as novel compounds, with some showing low micromolar potency versus pandemic \"swine\" H1N1 influenza (Eng195) in culture. Interestingly, a published adamantane-based M2-N31 inhibitor rapidly selected a resistant V27A polymorphism (M2-A27/N31), whereas this was not the case for non-adamantane compounds. Nevertheless, combinations of adamantanes and novel compounds achieved synergistic antiviral effects, and the latter synergised with the neuraminidase inhibitor (NAi), Zanamivir. Thus, site-directed drug combinations show potential to rejuvenate M2 as an antiviral target whilst reducing the risk of drug resistance.

microbiology↗