FEBS Letters最新文献

Human BRCA2 protects the DNA when replication forks stall, whereas MRE11-RAD50 and DNA2-WRN process or partially degrade these substrates. When mutated, these genes result in distinct genetic instabilities and cancers, arguing they have unique, not redundant, functions. Escherichia coli encodes functional homologs of MRE11-RAD50 (SbcC-SbcD), DNA2-WRN (RecJ-RecQ), and BRCA2 (RecF). Here, we use 2-dimensional gels, pulse-labelling, and replication-profiling analysis to show the bacterial homologs act at distinct substrates and loci on the chromosome. Whereas RecF and RecJ-RecQ protect and process DNA at arrested replication forks to facilitate repair, RecBCD and SbcC-SbcD protect and process DNA at sites where forks converge. Comparing the assays used in E. coli to human cells, we consider whether these cellular roles may be functionally conserved. Impact statement BRCA2, MRE11-RAD50, and WRN-DNA2 encode human proteins that process replication forks and result in distinct genetic instabilities and cancers when mutated. Here, we show their bacterial homologs act on unique replication fork substrates-those at DNA damage sites or as replication completes, and discuss their possible functional conservation in humans.

Ribonucleotide reductases (RNRs) convert all four ribonucleotides to deoxyribonucleotides, providing essential building blocks for DNA biosynthesis and repair through radical-based catalysis. These functions are key to cellular proliferation and have made RNRs well established targets for antimicrobial and antiviral drugs and combination chemotherapies. Here, we describe a novel highly sensitive one-pot enzymatic assay, which amplifies RNR activity by coupling it to the synthesis of a fluorogenic RNA aptamer. We validated this approach by testing RNR activity under dNTP-limiting conditions to emulate RNR's complex allosteric regulatory patterns and by detecting the dose- and time-dependent inhibition of RNR by hydroxyurea. This unique assay builds on previous high-throughput screening assays for investigation of RNR's catalytic mechanisms by improving sensitivity and reducing readout timeframes. Impact statement Ribonucleotide reductases (RNRs) are essential for controlling cellular dNTP supply and are major targets in cancer, antiviral, and antimicrobial therapy. FLARE is a novel single-tube, real-time RNR assay, coupling dNTP synthesis to the transcription of a fluorogenic aptamer for continuous monitoring of activity, regulation, and inhibition using standard microplate readers.

DNA double-strand break (DSB) repair is critical for genome stability and requires chromatin remodeling for efficient processing. Fun30, an ATP-dependent chromatin remodeler, promotes long-range DNA end resection to generate 3' overhangs, a key step in homologous recombination. Persistent DSBs relocate to the nuclear periphery, particularly through interactions with the inner nuclear membrane protein Mps3 and the nuclear pore complex component Nup84. By tracking a single irreparable break, we show that Fun30 facilitates this relocation. In fun30Δ cells, Mps3 and Nup84 enrichment at DSBs was reduced, indicating impaired tethering. We further demonstrate that Fun30 promotes deposition of the histone variant H2A.Z at DSBs. Thus, Fun30 favors relocation of persistent DSBs to the nuclear periphery by supporting resection and H2A.Z incorporation.

The Gram-negative pathogen Burkholderia pseudomallei possesses multiple resistance-nodulation-division superfamily transporters that contribute to multidrug resistance, including BpeB and BpeF. Structural studies of BpeB and BpeF have identified a hydrophilic patch in their substrate-binding pocket. To investigate the relationship between this hydrophilic patch and substrate specificity, mutant analyses were performed using an Escherichia coli recombinant expression system. Drug susceptibility tests of BpeB and BpeF mutants showed up to a 64-fold increase in susceptibility compared with the wild type. Growth curve analyses revealed that BpeB mutants exhibited increased resistance to aminoglycosides, which are not transported by the wild type. These findings suggest that the hydrophilic patches in the substrate-binding pockets of BpeB and BpeF are involved in the substrate specificity.

Collaboration has become an essential pillar of modern biological research. From international genome initiatives to interdisciplinary multi-omics projects, research in the life sciences increasingly relies on (multi)institutional teamwork. Yet, many collaborations fail to deliver on their promises of innovation, efficiency, and scientific impact. Morten T. Hansen's concept of 'disciplined collaboration' (2009) offers a valuable framework for understanding why collaboration sometimes hinders rather than helps research productivity. In this article, Hansen's principles are repurposed to the context of biological research in universities and research institutes. It is substantiated that selective, well-managed, and strategically aligned collaborations, rather than indiscriminate cooperations, lead to sustainable scientific advancement. The discussion of this paper explores the four major barriers to effective collaboration in academia, the three organizational levers proposed by Hansen, and the evaluative processes necessary for implementing disciplined collaboration in research environments. Finally, Hansen's views on institutional strategies are adapted to cultivate collaborative excellence within life science research in academic institutions.

The long lifespan of humans is often not matched with health span. Thus, there is a need for rejuvenation strategies. Here, we first discuss the evolutionary benefits of the long human lifespan, particularly when coupled with an extended health span. We then highlight the importance of understanding the complexity of aging before interfering with it. This raises the question of the optimal target for rejuvenation. We propose the blood system and hematopoietic stem cells (HSCs). Their decline is associated with dysfunction and disease in other organs, crystallizing them as a central player in organismal aging. We present rejuvenation strategies targeting the hematopoietic system, especially HSCs, and explore their systemic benefits. Overall, we summarize the potential of the blood system to reverse aging. Impact statement There is a current need to reduce the economic burden caused by aging-related diseases. In this perspective article, we discuss the evidence that supports that rejuvenating or delaying aging of the blood system has a beneficial and systemic impact on human health.

Cells are constantly exposed to various sources of DNA damage, including radiation, chemicals, replicative stress and oxidative stress, that threaten genome stability. To ensure faithful DNA repair, transcription regulation needs to be tightly controlled. This regulation involves transcriptional suppression, selective activation of DNA repair-related genes and transcriptional recovery post-repair. Failure to properly modulate transcription during DNA damage can result in collisions between transcriptional and repair machineries, misregulation of repair genes and delayed recovery, ultimately compromising genomic integrity. Chromatin modifications play a central role in this process. These modifications include phosphorylation, methylation, acetylation and ubiquitination, which orchestrate DNA accessibility for repair machinery and fine-tune transcriptional responses. Absence of these modifications leads to inefficient DNA repair and transcriptional errors that are implicated in diseases such as cancer, premature ageing and neurodegenerative disorders. In this review, we delve into the role of various types of histone modifications, such as phosphorylation, methylation, acetylation and ubiquitination and how they regulate transcription in response to DNA damage. Impact Statement This review elucidates how histone modifications orchestrate transcription regulation during DNA damage response, safeguarding genome stability. We also discuss transcription dysregulation in diseases such as cancer and premature aging. Our review provide insights on chromatin-based repair pathways and guide researchers in developing therapeutic targets.

Photosystem II (PSII) water oxidation includes proton and electron transfer pathways, occurring during the sequential S-state transitions of Mn₄CaO₆. Here, we investigate the charge separation events during the S₂ to S₃ transition that take place via the S₂TyrZ^• intermediate, utilizing electron paramagnetic resonance (EPR) spectroscopy. The increasing number of cycles of S₂TyrZ^• formation and decay results in a gradual diminution of the S₂TyrZ^• signal intensity which is proportional to the amount of S₃ state. Our results point to the progressive accumulation of a different configuration of the donor side of PSII at the S₂ state that allows the Mn₄CaO₆ to be oxidized. These results consolidate previous investigations supporting that, during the lifetime of the S₂TyrZ^•, a proton from Mn₄CaO₆ is removed, prior to the advancement to the S₃ state.

Bifidobacterium bifidum, a predominant colonizer of the infant gut, utilizes lacto-N-biose I (LNB), a prominent component of human milk oligosaccharides (HMOs), through a dedicated metabolic pathway. Among a diverse set of extracellular glycosidases involved in HMO degradation, lacto-N-biosidase (LnbB) plays a pivotal role by releasing LNB. We investigated the structure and function of the carbohydrate-binding module family 32 (CBM32) domain located at the C-terminus of the glycoside hydrolase family 20 catalytic domain in LnbB. Isothermal titration calorimetry showed that CBM32 binds LNB with a dissociation constant (K_d) of 98 μm. The crystal structure of the CBM32 complexed with LNB reveals the molecular basis for its specific recognition. Impact statement Bifidobacteria are beneficial gut microbes, and infant-associated strains establish symbiosis by degrading human milk oligosaccharides. This study uncovers the molecular mechanism by which Bifidobacterium bifidum captures lacto-N-biose I, a key disaccharide, functioning as a cross-feeder that promotes the growth of other bifidobacteria and supports the infant gut ecosystem.

Rising atmospheric CO₂ negatively affects plant iron (Fe) content, yet the underlying mechanisms remain poorly understood. Here, we identified More Iron under elevated CO₂ (MIC) as a new player involved in Fe homeostasis under elevated CO₂ in Arabidopsis thaliana. MIC is a previously uncharacterized transmembrane protein which we found predominantly localized to the Golgi apparatus. Loss of MIC function results in increased Fe content under elevated CO₂, effectively mitigating the Fe decline observed in plants. MIC protein abundance is reduced in roots under elevated CO₂, suggesting post-transcriptional regulation of protein stability. This work identifies MIC as a novel component in the plant response to elevated CO₂, with potential implications for improving the nutritional quality of crops under climate change.