FEBS Letters最新文献

Circadian rhythms are biological cycles of approximately 24 h that align physiology and behavior with the solar day, helping organisms coordinate their functions with the light/dark cycle. These rhythms are generated by molecular circadian clocks found in cells that are composed of transcription/translation negative feedback loops and regulate gene activity and protein production. The field of chemical biology has generated tools to track, modify, and manipulate clock proteins in living systems, providing a meaningful way to study these clocks and their components. Small molecules, covalent tags, and detectable reporters, among others, have been used to reveal how clocks keep time, respond to environmental signals, and differ across organisms. In this review, we highlight and describe chemical biology approaches used to study and modulate molecular circadian mechanisms that have expanded understanding of circadian protein dynamics and interactions in the contexts of mammalian and Drosophila models. The application of chemical biology strategies to study and target circadian clocks and their components can expand our fundamental knowledge via means that are otherwise inaccessible and point toward new strategies for treating clock-related disorders.

Terpene synthases (TPSs) generate complex hydrocarbon scaffolds through carbocationic cyclization cascades that demand precise active-site control to stabilize reactive intermediates. While π-cation and electrostatic interactions are established stabilizing factors, the role of methionine has remained unclear. Here, we identify a methionine-rich active site in hydropyrene synthase (HpS), a bacterial Class I TPS involved in pseudopterosin biosynthesis. Crystallography, mutagenesis, and multiscale QM/MM simulations reveal that methionine residues provide steric guidance and direct sulfur-carbocation stabilization during catalysis. Mutations alter product distributions, confirming functional relevance. Quantum chemical calculations indicate that sulfur-carbocation interactions are energetically comparable to π-carbocation interactions. These results uncover a previously unrecognized mechanism of carbocation stabilization in terpene biosynthesis.

Fused in sarcoma (FUS) forms phase-separated condensates implicated in amyotrophic lateral sclerosis (ALS). Although millimolar ATP concentrations paradoxically dissolve FUS condensates through hydrotropic activity, condensates nevertheless persist in cells, suggesting active regulatory mechanisms. Here, using a reconstituted system, we show that the AAA+ATPase valosin-containing protein (VCP) counteracts ATP-driven dissolution of FUS condensates. VCP preserved both wild-type and ALS-linked P525L condensates under high ATP conditions, and this protection required catalytic ATPase activity rather than stable partitioning into condensates. The effect was abolished by the D2-specific inhibitor ML240. Our findings establish direct biochemical evidence that VCP ATPase activity maintains FUS condensates under high ATP conditions, highlighting ATPase-driven enzymatic control of liquid-liquid phase separation as a potential general principle with implications for neurodegeneration.

The asymmetry of the phospholipids in the cell membrane is fundamental to maintaining normal cellular physiological functions. Phosphatidylserine (PS), a key phospholipid, is typically restricted to the inner side of the plasma membrane. However, during specific physiological or pathological processes such as apoptosis, PS rapidly flips to the cell surface, serving as an 'eat me' signal that mediates apoptotic cells' recognition. This process is catalyzed by a class of membrane proteins known as 'scramblases'. The Xk-related (Xkr) protein family, particularly Xkr8, has been identified as the main scramblase during apoptosis. As research has progressed in recent years, the functions of other Xkr family members (such as Xkr4 and Xkr9) have gradually come to light. They not only participate in apoptosis, but also play vital roles in various life processes, including nervous system development, auditory formation and tumor immunity. This article systematically reviews the discovery, molecular structure, activation mechanisms, and current research on the Xkr protein family. We also discuss future research directions, aiming to provide a comprehensive understanding of the functional diversity and regulatory networks of this emerging protein family.

Exposure to various environmental factors and endogenous agents can lead to double-strand DNA breaks. Bacteria are capable of restoring their genome integrity through a process known as the SOS response, which requires the RecA recombinase. Another protein critical for DNA repair is SMC-like RecN, which facilitates the location of the homologous DNA template by RecA. At present, the function and underlying mechanisms of RecN remain poorly understood. In this work, we use optical tweezers to demonstrate predominant binding of RecN to ssDNA and also show weak binding to dsDNA, resulting in a condition resembling DNA loop formation.

CFIm25, a key component of the cleavage factor Im (CFIm) complex needed for mRNA 3' end processing, shows increased protein expression during monocyte-to-macrophage differentiation despite stable mRNA levels. We demonstrate that poly(C)-binding protein 1 (PCBP1) suppresses CFIm25 translation in monocytes by binding to its long 3' untranslated region (UTR). During differentiation, alternative polyadenylation generates a shorter CFIm25 3'UTR lacking PCBP1 binding sites. RNA immunoprecipitation confirms PCBP1 binding to the long 3'UTR, while ribosome association analysis shows enhanced ribosome recruitment upon PCBP1 depletion. PCBP1 knockdown increases CFIm25 protein in undifferentiated cells and induces macrophage differentiation markers without stimulation. These findings reveal how alternative polyadenylation controls CFIm25 expression during immune cell differentiation by modulating RNA-binding protein interactions and provide insight into post-transcriptional regulation of RNA processing factors. Impact statement This work reveals how a key regulator of mRNA processing is itself controlled through a previously uncharacterized mechanism during immune cell differentiation. Our findings provide insights into the molecular circuits governing macrophage development and identify potential therapeutic targets for inflammatory disorders where myeloid cell differentiation is dysregulated.

Dysregulation of the transcription factor MYB plays a critical role in leukemia pathogenesis, progression, and prognosis; however, the detailed regulatory mechanisms of MYB remain unclear. Recently, we identified an enhancer long noncoding RNA (lncRNA) MY34UE-AS, which upregulates MYB expression. Here, we demonstrate that non-POU-domain-containing octamer binding protein (NONO) binds to MY34UE-AS through its RNA recognition motif 2 (RRM2) domain, thereby upregulating MYB expression and splicing. This interaction drives leukemia cell proliferation and migration. Our findings unveil a novel regulatory mechanism of MYB and propose the NONO-MY34UE-AS axis as a potential therapeutic target for leukemia. Impact statement Our study uncovers the NONO-MY34UE-AS-MYB regulatory axis in leukemia, revealing a new layer of MYB control. This mechanistic insight advances understanding of oncogenic transcription factor dysregulation and highlights potential therapeutic targets, offering new directions for leukemia research.

Aging is accompanied by profound changes in both the gut microbiome and the immune system, which engage in continuous, bidirectional communication. Alterations in microbial diversity and metabolism, particularly reductions in short-chain fatty acid (SCFA) producers as well as shifts in bile acid and tryptophan-metabolizing species, can incite and worsen inflammation, damage barrier integrity, and accelerate immunosenescence. Concomitantly, immune aging and reduced mucosal IgA promote microbial dysbiosis, forming a self-reinforcing cycle that fuels chronic inflammation ("inflammaging"). Microbial metabolites such as SCFAs, secondary bile acids, and indole derivatives play central roles in this gut-immune dialog, influencing regulatory T-cell balance, epithelial repair, and neurological health through the gut-brain axis. Emerging evidence suggests that diet, probiotics, postbiotics, and microbiome transplantations can restore beneficial microbial and, consequently, immune functions, offering opportunities to promote healthy aging and potentially reverse adverse symptoms. Understanding and targeting the gut microbiome-immune feedback loops may reveal new strategies to modulate inflammaging and extend health span.

Post-translational modifications regulate tau aggregation and propagation, yet how amyloid pathology shapes the tau modification landscape remains unclear. Using liquid chromatography-tandem mass spectrometry, we compared tau modifications in MAPT knock-in (MAPT KI) mice and MAPT/App double knock-in mice with App^NL-G-F amyloid pathology. Only subtle differences were detected, with a tendency toward increased acetylation within the repeat domain. Because K321 and K331 lie in the fibril-forming core, their roles were further examined. Acetylation at these sites was absent in cynomolgus monkey brains. To test functional relevance, we generated acetylation-mimicking MAPT^K331Q knock-in mice on the MAPT KI background. Despite tau expression, these mice showed reduced tau phosphorylation at 24 months, with unchanged insoluble tau and seeding activity. Thus, K331 acetylation does not promote tau pathology.

The proteins Inturned and Fuzzy are members of the tri-longin domain (TLD) RabGEF family and activate the GTPase Rab23 downstream of the core planar cell polarity (PCP) proteins Vangl2 and Prickle. To gain insight into the function of a predicted PDZ domain unique to Inturned among TLD proteins, we performed structural and biochemical characterisations. We show that this domain does not interact with membranes or Vangl2. Instead, we find a phosphorylation-dependent interaction between Vangl2 and a PDZ domain of the apical-basal polarity protein Scribble. A crystal structure of Intu-PDZ reveals a unique PDZ-like fold lacking an interaction site for PDZ-binding motifs. Our data provide new insight into the role of PDZ domains in coordinating cell polarity downstream of Vangl2.