FEBS Letters最新文献

Dipeptidyl peptidase IV (DPPIV) family proteases are classically defined by their strict removal of N-terminal dipeptides from substrates bearing a proline or alanine at the P₁ position. Here, we report that both Caenorhabditis elegans DPF-3 and human DPP4 (hDPP4) possess previously unrecognized tripeptidyl peptidase activity in addition to dipeptidyl peptidase activity. This activity plays a key role in the processing of the WAGO-1 protein N-terminus, which is essential for proper small-RNA loading, germline genome defense, and fertility. Kinetic analyses using the fluorogenic substrate H-Met-Gly-Pro-AMC further demonstrated that, in vitro, DPF-3 and hDPP4 can liberate AMC. These findings potentially expand the substrate repertoire of DPPIV proteases, suggesting that these proteases could function as versatile N-terminal processors, with important implications for nascent protein maturation.

Universal stress proteins (USPs) have remained an enigma since their first description by Nystrom and Neidhardt in 1992. Despite being upregulated under diverse stresses and found across a range of bacterial species, decades of studies suggested only general and potentially redundant protective functions for USPs. Recent studies have uncovered that USPs are critical regulators of bacterial survival processes in Actinobacteria, most notably in Mycobacterium tuberculosis, one of the most prolific and lethal of human pathogens. This brief review places these recent studies in the context of earlier publications and discusses their importance for future USP research, our understanding of these regulatory proteins, and novel therapeutic options that these proteins present in Mycobacterium tuberculosis, related Actinobacteria, and across diverse bacterial species. Impact Statement Universal stress proteins (USPs) have recently been directly implicated in survival processes in Mycobacteria, related Actinobacteria, and multiple bacterial pathogens. This new understanding identifies these stress-responsive proteins as important targets for mechanistic studies in bacterial survival and promising targets for novel antimicrobial therapeutics.

The maintenance of protein homeostasis is a fundamental premise for the survival of all life. The synthesis, folding, localization, and degradation of thousands of proteins must be organized according to various conditions. To ensure such a stable and functional proteome, the proteostasis network evolved. Dedicated to this, the fourth School on Proteostasis, a co-funded EMBO|FEBS Lecture Course in memory of Susan Lindquist, took place in Espoo, Finland on 16-19 September 2025, with 59 early career researchers (PhD students or postdoctoral fellows), 18 leading scientists, and two editors attending and discussing the current state of the field. From basic principles to the latest therapeutic developments, this meeting provided a comprehensive overview of proteostasis. This report summarizes the lecture course and highlights selected presentations.

SETDB1, a H3K9 methyltransferase involved in nuclear transcriptional silencing, also localizes to the cytoplasm through unclear mechanisms. Here, we identify cell density as key regulator of SETDB1 subcellular localization and demonstrate its role in modulating the Hippo signaling pathway. Under low-density culture, SETDB1 distributes between nucleus and cytoplasm, whereas high-density culture triggers nuclear exclusion and proteasomal degradation. SETDB1 depletion reduces YAP1 phosphorylation and increases nuclear YAP1 accumulation. Transcriptomic analysis of SETDB1 knockout cells revealed upregulation of YAP1-TEAD1 target genes (YTGs). Immunoprecipitation experiments showed that SETDB1 is recruited to YTG promoters via TEAD1 and competes with YAP1 for TEAD1 binding. These findings reveal that SETDB1 regulates Hippo pathway output through YAP1 phosphorylation modulation and competitive transcriptional repression.

The tumor suppressor p53 is normally maintained at low levels through MDM2-mediated degradation; however, this regulation becomes ineffective upon DNA damage, leading to p53 phosphorylation and accumulation. This study shows that E6-associated protein (E6AP) provides an alternative regulatory pathway during genotoxic stress. Unlike MDM2, E6AP can effectively decrease p53 levels in HepG2 cells exposed to DNA-damaging agents, such as etoposide. Additionally, E6AP specifically targets p53 phosphorylated at serine-15, promoting its proteasomal degradation, whereas MDM2 cannot. This phosphorylation-dependent regulation by E6AP helps maintain p53 at appropriate levels during mild DNA damage, preventing excessive accumulation that could threaten cell survival, while still allowing for necessary stress responses. Impact statement The mechanism by which p53 is negatively regulated under genotoxic stress is largely unknown. E6-associated protein (E6AP), unlike MDM2, downregulates p53 levels following exposure to etoposide. E6AP specifically targets p53 phosphorylated at Ser-15. This mechanism prevents excessive accumulation of p53 that could otherwise reach lethal levels.

The HtrA family of proteins is known for its dual role as chaperones and proteases. In Helicobacter pylori (H. pylori), HtrA's chaperone and proteolytic activities are crucial for the bacterium's survival and successful host infection. Compared to other HtrA homologs in Gram-negative bacteria, HtrA of H. pylori (HtrA_Hp) is rather well-understood. HtrA is localized in two cellular compartments, performing critical functions within the bacterial periplasm as well as in the extracellular milieu. This review aimed to summarize the current knowledge on HtrA_Hp and provide comprehensive information about (i) the structure, oligomerization, and general properties of HtrA_Hp, (ii) its chaperone and proteolytic activity in the stress response and the protein quality control system in the periplasm, and (iii) the functional role of HtrA_Hp in opening lateral cell junction complexes of epithelial cells as an important step in infectivity. Due to its essential physiological role and its contribution to the pathologic consequences of infection, HtrA represents a highly attractive target for novel therapeutic strategies.

CRISPR-Cas systems provide adaptive immunity to bacteria by recognizing and destroying foreign genetic elements. The type I-E CRISPR-Cas system utilizes a multi-subunit Cascade complex to detect target DNA and recruit the Cas3 nuclease for degradation. To overcome this defense, bacteriophages have evolved anti-CRISPR (Acr) proteins that inhibit various steps of the CRISPR interference pathway. Here, we determined the crystal structure of AcrIE8.1, an uncharacterized Acr, revealing it binds to Cas11, a Cascade subunit, to disrupt function. AcrIE8.1 has a compact fold with a defined Cas11-binding interface, suggesting a unique inhibitory mechanism among AcrIE proteins. These findings highlight Cas11 as a critical target for Acr-mediated immune evasion. Impact statement Through a combination of structural and biochemical analyses, we demonstrate that AcrIE8.1 directly binds to the Cas11 subunit of the Cascade complex to inhibit the CRISPR-Cas system. This represents a novel inhibitory strategy not previously observed among AcrIE proteins.

Lentiviral vectors are powerful tools for long-term expression of large genes in the mammalian brain, but the palette of lentiviral tools available for targeting specific cell subpopulations is restricted. We describe a lentiviral vector for neuronal subtype-specific expression in Cre mouse lines. Combining a Cre-dependent flip excision switch with a GFP and a 2A self-cleaving peptide, it enables identification of living neurons expressing a gene of interest using fluorescence. We validated this vector by targeting neocortical interneuron types and midbrain dopaminergic neurons. Gene expression occurred exclusively in Cre-expressing neurons without altering their basic electrophysiological properties. This system has been designed to be flexible and easy to modify in order to target expression of any gene of interest in any cell subtype.

HipA-like kinases are widespread bacterial serine-threonine kinases, yet their regulatory mechanisms remain poorly understood. Here, we characterise two novel HipA-like systems, the monocistronic hipL and bicistronic hipIN, also encoding HipS-like and HIRAN domains. We show that the hipL gene contains an internal translation initiation site producing a smaller variant, HipL_S, which counteracts HipL-mediated toxicity via its HipS-like domain. Contrary to this, HipN requires both the HipS-like and the HIRAN domains to neutralise HipI-mediated toxicity. Neither system forms stable toxin-antitoxin (TA) complexes in vitro, distinguishing them from classical type II systems. Finally, we show that autophosphorylation affects HipL but not HipI-mediated toxicity. These findings reveal diverse regulatory architectures in HipA-like TA systems, shaped by domain composition and operon structure. Impact statement Kinases are increasingly recognised as key regulators in bacteria. Here, we show how complex operon and domain structures can contribute to kinase function and regulation, revealing increasingly complex regulatory networks in microbes.

The mechanisms supporting progression of metastatic prostate cancer (PCa) in adipocyte-rich bone marrow remain unclear. We hypothesized that stearoyl-coenzyme A desaturase (SCD) promotes PCa survival in bone by modulating stress responses and regulating lipid peroxidation. We show that SCD-high PCa cells are sensitive to SCD loss, showing smaller spheroids, reduced mTOR signaling, and elevated endoplasmic reticulum (ER) stress. SCD expression is further augmented by adipocytes, and SCD loss induces DNA damage and repair activation only with adipocyte exposure. In vivo, pharmacological SCD inhibition reduces tumor size and increases ER stress and DNA damage in SCD-high-expressing bone tumors. These findings suggest SCD plays a role in redox regulation and DNA repair sensitivity, with therapeutic potential for targeting DNA repair pathways in combination with SCD inhibition. Impact statement This study reveals that stearoyl-CoA desaturase (SCD) supports prostate cancer growth in adipocyte-rich bone by regulating redox balance and DNA repair responses, uncovering a metabolic mechanism linking lipid metabolism to genomic stability and suggesting therapeutic potential for combining SCD and DNA repair pathway inhibition.