Biology subjects

Trunk, K.

Publications and source records attributed to Trunk, K..

3 recordsLinked to original sources

bioRxiv2025

The Type VI Secretion System Antifungal Effector Tfe2 Inhibits Protein Translation and Drives Hyperactivation of TORC1.

Type VI Secretion Systems (T6SS) are utilised by many bacteria to deliver toxic effectors into neighbouring bacterial, fungal or host cells. Whilst many antibacterial effectors are well characterised, much less is known regarding the identity or mode-of-action of antifungal effectors. Here we combine structural modelling with proteomics and in vivo approaches, to show that the Serratia marcescens antifungal effector Tfe2 adopts a novel fold and functions as a potent inhibitor of protein translation leading to hyperactivation of the TORC1 kinase. We show that Tfe2 expression in Saccharomyces cerevisiae, or treatment with the protein translation inhibitor cycloheximide, drive identical increases in free intracellular amino acids and hyperactivation of TORC1. This, in turn, triggers the Tfe2 and cycloheximide-mediated rapid turnover of amino acid transporters through stimulating substrate-independent endocytosis. Polysome profiling, however, revealed differences in Tfe2 and cycloheximide-mediated protein translation inhibition, with Tfe2 inhibiting initiation of translation. Tfe2-mediated hyperactivation of TORC1 may also underpin adaptive responses to this effector which include significant remodelling of the lipidome and notable alterations in organelle and cell wall structures. Collectively this study has provided new insight into the mode-of-action of a structurally novel antifungal effector Tfe2.

microbiology↗

bioRxiv2024

Unbiased functional genetic screens reveal essential RNA modifications in human cancer and drug resistance

RNA modification pathways are mis-regulated in multiple types of human cancer. To comprehensively identify cancer-relevant RNA modifications and their regulators, we screened all 150 annotated human RNA modifying proteins across 18 different normal and cancer cell lines using a CRISPR-based genetic knockout system. Fifty RNA modifying proteins were essential for survival of at least one cell type. A third of these essential genes were amplified in 38 different human primary cancer types and potentially drive cancer growth. Unexpectedly, the number of essential genes per cell line varied considerably, and this variation was not due to tissue of origin. Instead, we found that cancer cell-specific mitochondrial metabolic plasticity was responsible for the unique requirement of certain RNA modifications. For example, leukemia cells with high intrinsic drug tolerance required mitochondrial flexibility to survive treatment with the anti-leukemic drugs cytarabine and venetoclax. Synthetic lethality screens revealed that drug-resistance is abolished by deleting the mitochondrial methyltransferase TRMT5, which is responsible for the formation of N1-methylguanosine (m1G) in the tRNA anticodon loop. In summary, our study identifies cancer-relevant RNA modifying enzymes, and reveals a novel promising drug target for therapy-resistant acute myeloid leukemia.

cell biology↗

bioRxiv2019

A new family of Type VI secretion system-delivered effector proteins displays ion-selective pore-forming activity

Type VI secretion systems (T6SSs) are nanomachines widely used by bacteria to compete with rivals. T6SSs deliver multiple toxic effector proteins directly into neighbouring cells and play key roles in shaping diverse polymicrobial communities. A number of families of T6SS-dependent anti-bacterial effectors have been characterised, however the mode of action of others remains unknown. Here we report that Ssp6, an anti-bacterial effector delivered by the Serratia marcescens T6SS, is an ion-selective pore-forming toxin. In vivo, Ssp6 inhibits growth by causing depolarisation of the inner membrane of intoxicated cells and also leads to increased outer membrane permeability, whilst reconstruction of Ssp6 activity in vitro demonstrated that it forms cation-selective pores. A survey of bacterial genomes revealed that Ssp6-like effectors are widespread in Enterobacteriaceae and often linked with T6SS genes. We conclude that Ssp6 represents a new family of T6SS-delivered anti-bacterial effectors, further diversifying the portfolio of weapons available for deployment during inter-bacterial conflict.

microbiology↗