ATGL is a biosynthetic enzyme for fatty acid esters of hydroxy fatty acids.

Branched fatty acid (FA) esters of hydroxy FAs (HFAs; FAHFAs) are recently discovered lipids that are conserved from yeast to mammals1,2. A subfamily, palmitic acid esters of hydroxy stearic acids (PAHSAs), are anti-inflammatory and anti-diabetic1,3. Humans and mice with insulin resistance have lower PAHSA levels in subcutaneous adipose tissue and serum1. PAHSA administration improves glucose tolerance and insulin sensitivity and reduces inflammation in obesity, diabetes and immune-mediated diseases1,4-7. The enzyme(s) responsible for FAHFA biosynthesis in vivo remains unknown. Here we identified adipose triglyceride lipase (ATGL, also known as patatin-like phospholipase domain containing 2 (PNPLA2)) as a candidate biosynthetic enzyme for FAHFAs using chemical biology and proteomics. We discovered that recombinant ATGL uses a transacylation reaction that esterifies an HFA with a FA from triglyceride (TG) or diglyceride to produce FAHFAs. Overexpression of wild-type, but not catalytically dead, ATGL increases FAHFA biosynthesis. Chemical inhibition of ATGL or genetic deletion of Atgl inhibits FAHFA biosynthesis and reduces the levels of FAHFA and FAHFA-TG. Levels of endogenous and nascent FAHFAs and FAHFA-TGs are 80-90 per cent lower in adipose tissue of mice in which Atgl is knocked out specifically in the adipose tissue. Increasing TG levels by upregulating diacylglycerol acyltransferase (DGAT) activity promotes FAHFA biosynthesis, and decreasing DGAT activity inhibits it, reinforcing TGs as FAHFA precursors. ATGL biosynthetic transacylase activity is present in human adipose tissue underscoring its potential clinical relevance. In summary, we discovered the first, to our knowledge, biosynthetic enzyme that catalyses the formation of the FAHFA ester bond in mammals. Whereas ATGL lipase activity is well known, our data establish a paradigm shift demonstrating that ATGL transacylase activity is biologically important.

An enzymatic Alder-ene reaction.

An ongoing challenge in chemical research is to design catalysts that select the outcomes of the reactions of complex molecules. Chemists rely on organocatalysts or transition metal catalysts to control stereoselectivity, regioselectivity and periselectivity (selectivity among possible pericyclic reactions). Nature achieves these types of selectivity with a variety of enzymes such as the recently discovered pericyclases-a family of enzymes that catalyse pericyclic reactions1. Most characterized enzymatic pericyclic reactions have been cycloadditions, and it has been difficult to rationalize how the observed selectivities are achieved2-13. Here we report the discovery of two homologous groups of pericyclases that catalyse distinct reactions: one group catalyses an Alder-ene reaction that was, to our knowledge, previously unknown in biology; the second catalyses a stereoselective hetero-Diels-Alder reaction. Guided by computational studies, we have rationalized the observed differences in reactivities and designed mutant enzymes that reverse periselectivities from Alder-ene to hetero-Diels-Alder and vice versa. A combination of in vitro biochemical characterizations, computational studies, enzyme co-crystal structures, and mutational studies illustrate how high regioselectivity and periselectivity are achieved in nearly identical active sites.

A class of anti-inflammatory lipids decrease with aging in the central nervous system.

Lipids contribute to the structure, development, and function of healthy brains. Dysregulated lipid metabolism is linked to aging and diseased brains. However, our understanding of lipid metabolism in aging brains remains limited. Here we examined the brain lipidome of mice across their lifespan using untargeted lipidomics. Co-expression network analysis highlighted a progressive decrease in 3-sulfogalactosyl diacylglycerols (SGDGs) and SGDG pathway members, including the potential degradation products lyso-SGDGs. SGDGs show an age-related decline specifically in the central nervous system and are associated with myelination. We also found that an SGDG dramatically suppresses LPS-induced gene expression and release of pro-inflammatory cytokines from macrophages and microglia by acting on the NF-κB pathway. The detection of SGDGs in human and macaque brains establishes their evolutionary conservation. This work enhances interest in SGDGs regarding their roles in aging and inflammatory diseases and highlights the complexity of the brain lipidome and potential biological functions in aging.

Author Correction: CasX enzymes comprise a distinct family of RNA-guided genome editors.

In this Article, owing to issues with the first 30 nucleotides of the sgRNA, which run in the opposite direction, corrections have been made to the Protein Data Bank (PDB) accessions in the 'Data availability' section, and this also affects Figs. 3, 4, Extended Data Fig. 6, Supplementary Table 1 and Supplementary Video 1. The original Article has been corrected online. See the accompanying Amendment for further details.

CasX enzymes comprise a distinct family of RNA-guided genome editors.

The RNA-guided CRISPR-associated (Cas) proteins Cas9 and Cas12a provide adaptive immunity against invading nucleic acids, and function as powerful tools for genome editing in a wide range of organisms. Here we reveal the underlying mechanisms of a third, fundamentally distinct RNA-guided genome-editing platform named CRISPR-CasX, which uses unique structures for programmable double-stranded DNA binding and cleavage. Biochemical and in vivo data demonstrate that CasX is active for Escherichia coli and human genome modification. Eight cryo-electron microscopy structures of CasX in different states of assembly with its guide RNA and double-stranded DNA substrates reveal an extensive RNA scaffold and a domain required for DNA unwinding. These data demonstrate how CasX activity arose through convergent evolution to establish an enzyme family that is functionally separate from both Cas9 and Cas12a.

Smurf1 polyubiquitinates on K285/K282 of the kinases Mst1/2 to attenuate their tumor-suppressor functions.

Sterile 20-like kinases Mst1 and Mst2 (Mst1/2) and large tumor suppressor 1/2 are core kinases to mediate Hippo signaling in maintaining tissue homeostasis. We have previously demonstrated that Smad ubiquitin (Ub) regulatory factor 1 (Smurf1), a HECT-type E3 ligase, ubiquitinates and in turn destabilizes large tumor suppressor 1/2 to induce the transcriptional output of Hippo signaling. Here, we unexpectedly find that Smurf1 interacts with and polyubiquitinates Mst1/2 by virtue of K27- and K29-linked Ub chains, resulting in the proteasomal degradation of Mst1/2 and attenuation of their tumor-suppressor functions. Among the potential Ub acceptor sites on Mst1/2, K285/K282 are conserved and essential for Smurf1-induced polyubiquitination and degradation of Mst1/2 as well as transcriptional output of Hippo signaling. As a result, K285R/K282R mutation of Mst1/2 not only negates the transcriptional output of Hippo signaling but enhances the tumor-suppressor functions of Mst1/2. Together, we demonstrate that Smurf1-mediated polyubiquitination on K285/K282 of Mst1/2 destabilizes Mst1/2 to attenuate their tumor-suppressor functions. Thus, the present study identifies Smurf1-mediated ubiquitination of Mst1/2 as a hitherto uncharacterized mechanism fine-tuning the Hippo signaling pathway and may provide additional targets for therapeutic intervention of diseases associated with this important pathway.

Construction and efficacy testing of DNA vaccines containing HLA-A*02:01-restricted SARS-CoV-2 T-cell epitopes predicted by immunoinformatics.

Vaccines play essential roles in the fight against the COVID-19 pandemic. The development and assessment of COVID-19 vaccines have generally focused on the induction and boosting of neutralizing antibodies targeting the SARS-CoV-2 spike (S) protein. Due to rapid and continuous variation in the S protein, such vaccines need to be regularly updated to match newly emerged dominant variants. T-cell vaccines that target MHC I- or II-restricted epitopes in both structural and non-structural viral proteins have the potential to induce broadly cross-protective and long-lasting responses. In this work, the entire proteome encoded by SARS-CoV-2 (Wuhan-hu-1) is subjected to immunoinformatics-based prediction of HLA-A*02:01-restricted epitopes. The immunogenicity of the predicted epitopes is evaluated using peripheral blood mononuclear cells from convalescent Wuhan-hu-1-infected patients. Furthermore, predicted epitopes that are conserved across major SARS-CoV-2 lineages and variants are used to construct DNA vaccines expressing multi-epitope polypeptides. Most importantly, two DNA vaccine constructs induce epitope-specific CD8 + T-cell responses in a mouse model of HLA-A*02:01 restriction and protect immunized mice from challenge with Wuhan-hu-1 virus after hACE2 transduction. These data provide candidate T-cell epitopes useful for the development of T-cell vaccines against SARS-CoV-2 and demonstrate a strategy for quick T-cell vaccine candidate development applicable to other emerging pathogens.

Influence of ambient temperature on the CO2 emitted of light-duty vehicle.

Because of global warming, people have paid more attention to greenhouse gas emitted by vehicles. To quantify the impact of temperature on vehicle CO2 emissions, this study was conducted using the world light vehicle test cycle on two light-duty E10 gasoline vehicles at ambient temperatures of -10, 0, 23, and 40℃, and found that CO2 emission factors of Vehicle 1 in the low-speed phase were 22.07% and 20.22% higher than those of Vehicle 2 at cold start and hot start under -10℃. The reason was vehicle 1 had a larger displacement and more friction pairs than vehicle 2. There was the highest CO2 emission at the low-speed phase due to low average speed, frequent acceleration, and deceleration. The CO2 temperature factor and the ambient temperature had a strong linear correlation (R2 = 0.99). According to CO2 temperature factors and their relationships, CO2 emission factors of other ambient temperatures could be calculated when the CO2 emission factor of 23℃ was obtained, and the method also could be used to obtain the CO2 temperature factors of different vehicles. To separate the effect of load setting and temperature variation on CO2 emission quantitatively, a method was proposed. And results showed that the load setting was dominant for the CO2 emission variation. Compared with 23℃, the CO2 emission for vehicle 1 caused by load setting variation were 62.83 and 47.42 g/km, respectively at -10 and 0℃, while those for vehicle 2 were 45.01 and 35.63 g/km, respectively.

Horizontal Transport in Ti3C2Tx MXene for Highly Efficient Osmotic Energy Conversion from Saline-Alkali Environments.

Osmotic energy from the ocean has been thoroughly studied, but that from saline-alkali lakes is constrained by the ion-exchange membranes due to the trade-off between permeability and selectivity, stemming from the unfavorable structure of nanoconfined channels, pH tolerance, and chemical stability of the membranes. Inspired by the rapid water transport in xylem conduit structures, we propose a horizontal transport MXene (H-MXene) with ionic sequential transport nanochannels, designed to endure extreme saline-alkali conditions while enhancing ion selectivity and permeability. The H-MXene demonstrates superior ion conductivity of 20.67 S m-1 in 1 M NaCl solution and a diffusion current density of 308 A m-2 at a 10-fold salinity gradient of NaCl solution, significantly outperforming the conventional vertical transport MXene (V-MXene). Both experimental and simulation studies have confirmed that H-MXene represents a novel approach to circumventing the permeability-selectivity trade-off. Moreover, it exhibits efficient ion transport capabilities, addressing the gap in saline-alkali osmotic power generation.

Enzymatic cis-Decalin Formation in Natural Product Biosynthesis.

Stereoselective synthesis of cis-decalin structures using [4 + 2] cycloaddition is challenging. We explored the biosynthetic pathway of the fungal natural product fischerin (1) to identify a new pericyclase FinI that can catalyze such a reaction. The cocrystal structure of FinI, a predicted O-methyltransferase, with the product and SAM provides insight into cis-decalin formation in nature.

Molecular Engineering of Ordered Piezoelectric Sulfonic Acid-Containing Assemblies.

Sulfonic acid-containing bioorganic monomers with wide molecular designability and abundant hydrogen bonding sites hold great potential to design diverse functional biocrystals but have so far not been explored for piezoelectric energy harvesting applications due to the lack of strategies to break the centrosymmetry of their assemblies. Here, a significant molecular packing transformation from centrosymmetric into non-centrosymmetric conformation by the addition of an amide terminus in the sulfonic acid-containing bioorganic molecule is demonstrated, allowing a high electromechanical response. The amide-functionalized molecule self-assembles into a polar supramolecular parallel ß-sheet-like structure with a high longitudinal piezoelectric coefficient d11 = 15.9 pm V-1 that produces the maximal open-circuit voltage of >1 V and the maximal power of 18 nW in nanogenerator devices pioneered. By contrast, molecules containing an amino or a cyclohexyl terminus assemble into highly symmetric 3D hydrogen bonding diamondoid-like networks or 2D double layer structures that show tunable morphologies, thermostability, and mechanical properties but non-piezoelectricity. This work not only presents a facile approach to achieving symmetry transformation of bioorganic assemblies but also demonstrates the terminal group and the property correlation for tailor-made design of high-performance piezoelectric biomaterials.

Prospecting for natural products by genome mining and microcrystal electron diffraction.

More than 60% of pharmaceuticals are related to natural products (NPs), chemicals produced by living organisms. Despite this, the rate of NP discovery has slowed over the past few decades. In many cases the rate-limiting step in NP discovery is structural characterization. Here we report the use of microcrystal electron diffraction (MicroED), an emerging cryogenic electron microscopy (CryoEM) method, in combination with genome mining to accelerate NP discovery and structural elucidation. As proof of principle we rapidly determine the structure of a new 2-pyridone NP, Py-469, and revise the structure of fischerin, an NP isolated more than 25 years ago, with potent cytotoxicity but hitherto ambiguous structural assignment. This study serves as a powerful demonstration of the synergy of MicroED and synthetic biology in NP discovery, technologies that when taken together will ultimately accelerate the rate at which new drugs are discovered.

Economical synthesis of γ-cyclodextrin catalyzed by oriented cyclodextrin glycosyltransferase displayed on bacterial polyhydroxyalkanoate nanogranules.

BACKGROUND: The advantages of γ-cyclodextrin (γ-CD) include its high solubility, ability to form inclusion complexes with various poorly water-soluble molecules, and favorable toxicological profile; thus, γ-CD is an attractive functional excipient widely used in many industrial settings. Unfortunately, the high cost of γ-CD caused by the low activity and stability of γ-cyclodextrin glycosyltransferase (γ-CGTase) has hampered large-scale production and application. RESULTS: This study reports the in vivo one-step production of immobilized γ-CGTase decorated on the surface of polyhydroxyalkanoate (PHA) nanogranules by the N-terminal fusion of γ-CGTase to PHA synthase via a designed linker. The immobilized γ-CGTase-PHA nanogranules showed outstanding cyclization activity of 61.25 ± 3.94 U/mg (γ-CGTase protein) and hydrolysis activity of 36,273.99 ± 1892.49 U/mg, 44.74% and 18.83% higher than that of free γ-CGTase, respectively. The nanogranules also exhibited wider optimal pH (cyclization activity 7.0-9.0, hydrolysis activity 10.0-11.0) and temperature (55-60 °C) ranges and remarkable thermo- and pH-stability, expanding its utility to adapt to wider and more severe reaction conditions than the free enzyme. A high yield of CDs (22.73%) converted from starch and a high ratio (90.86%) of γ-CD in the catalysate were achieved at pH 9.0 and 50 °C for 10 h with 1 mmol/L K+, Ca2+, and Mg2+ added to the reaction system. Moreover, γ-CGTase-PHA beads can be used at least eight times, retaining 82.04% of its initial hydrolysis activity and 75.73% of its initial cyclization activity. CONCLUSIONS: This study provides a promising nanobiocatalyst for the cost-efficient production of γ-CD, which could greatly facilitate process control and economize the production cost.

Identification of biomolecule-based electronic materials from a first-principles study of aliphatic amino acids.

Biomolecule-based electronic materials can enable health innovations by virtue of their intrinsic bioactivity and physical properties. However, the ultra-wide bandgap and limited piezoelectric properties of most biomaterials prevent them from reaching their full potential. Herein, the electronic structures and electromechanical properties of aliphatic amino acid crystals are investigated based on density functional theory. L-Met is found to be a wide bandgap p-type semiconductor, and the much-reduced bandgap of 2.88 eV is ascribed to the sulphur atoms in L-Met. L-Leu has a shear piezoelectric voltage constant of 2.706 V mN-1 that is over an order of magnitude higher than that of lead zirconate titanate, and good toughness and ductility are also revealed in L-Leu from mechanical property investigations. This study illustrates a computational approach to find smart and multifunctional biomaterials and inspire their growth and applications.

Kidney cancer with thyroid metastasis combined with thyroid carcinoma, a case report.

BACKGROUND: Thyroid cancer is the most common malignant tumor of the endocrine system. There have been some reports on kidney cancer with thyroid metastasis. However, kidney cancer has rarely been detected during thyroid cancer surgery. CASE PRESENTATION: We present a rare case of kidney cancer with thyroid metastasis, combined with thyroid carcinoma. A 66-year-old woman was admitted to our hospital in September 2021 due to enlarged left thyroid nodules for two years. The patient was diagnosed with a left thyroid nodule on physical examination in 2012. Extended radical resection of the thyroid cancer was performed. Intraoperatively, two thyroid lesions were identified. Thus, the patient was definitively diagnosed with kidney cancer with thyroid metastasis and papillary thyroid carcinoma. Furthermore, two metastatic nodules due to kidney cancer and one metastatic lymph node lesion due to thyroid cancer were found in the loose connective tissue adjacent to the thyroid. CONCLUSIONS: Kidney cancer with thyroid metastasis and thyroid carcinoma rarely co-occur, and it is difficult to identify the primary tumor. Although clinical examination methods are increasingly updated, the past medical history and physical examination are still very important.

First Report of Fusarium oxysporum Causing Leaf Wilt on Dinteranthus vanzylii (Green Stone Plant) in China.

Dinteranthus vanzylii is a low-growing species in the family Aizoaceae, native to southern Africa, with a pair of thick grey leaves covered with dark red spots and stripes. This stone-like succulent grows near the ground, which may protect it from water evaporation and herbivores. Dinteranthus vanzylii has become popular in China due to its attractive appearance and easy indoor cultivation. In September 2021, 7% of D. vanzylii (approximately 140 pots) showed leaf wilt symptoms in a commercial greenhouse located in Ningde (119°35'39.696″E, 27°23'30.556″N), Fujian Province, China. The diseased plants were shrivelling and eventually underwent necrosis. Their leaf tissues were rotting and carpeted with white mycelium. The leaf tissues of 10 symptomatic plants were cut into 0.5 cm2 pieces, surface-sterilized and placed on PDA medium. According to the colony morphology after 7 days of culture, 20 fungal isolates with abundant whitish aerial mycelium were divided into two types: 8 isolates produced lilac pigment whereas 12 did not. Both produced unicellular ovoid microconidia, sickled-shaped macroconidia with 3 - 4 septa and single or paired smooth, thick-walled chlamydospores on carnation leaf agar (CLA). Molecular identification based on DNA sequences from EF1-α (O'Donnell et al. 1998), RPB1 and RPB2 (O'Donnell et al. 2010) revealed 100% identity among isolates within each group; however, there were several base differences between two types. Sequences of representative isolates KMDV1 and KMDV2 were deposited in GenBank (acc. nos.: OP910243, OP910244, OR030448, OR030449, OR030450 and OR030451), which showed 99.10% - 99.74% identity with different F. oxysporum strains (GenBank acc. nos.: KU738441, LN828039, MN457050, MN457049, ON316742 and ON316741). Phylogenetic tree inferred from the concatenated EF1-α, RPB1 and RPB2 revealed that these isolates clustered with F. oxysporum. Thus, these isolates were identified as F. oxysporum. Using a root-drenching method, 10 one-year-old healthy D. vanzylii were inoculated in conidial suspensions (1*106 conidia/mL) of isolates KMDV1 and KMDV2 for 60 min, respectively. They were transplanted into pots with sterilized soil and incubated in a plant-growth chamber at 25°C and 60% relative humidity. Control plants were treated with sterilized water. The pathogenicity test was repeated three times. All plants inoculated with each isolate developed leaf wilt symptoms after 15 days and were dead after 20 - 30 days. However, no symptoms were observed in the control plants. Fusarium oxysporum was reisolated and confirmed based on morphology and EF1-α sequence analysis. No pathogens were isolated from the control plants. This is the first report of F. oxysporum causing leaf wilt disease on D. vanzylii in China. To date, several diseases have been reported on members of the Aizoaceae. For instance, collar and stem rot on Lampranthus sp. caused by Pythium aphanidermatum (Garibaldi et al. 2009), wilt on Lampranthus sp. and Tetragonia tetragonioides caused by Verticillium dahliae (Garibaldi et al. 2010; Garibaldi et al. 2013), and leaf spot on Sesuvium portulacastrum caused by Gibbago trianthemae (Chen et al., 2022). Our research could provide insight into fungal diseases on members of the Aizoaceae and contribute to their cultivation and management.

A new phenotype of syndromic retinitis pigmentosa with myopathy is caused by mutations in retinol dehydrogenase 11.

Retinol dehydrogenase 11 (RDH11) is an 11-cis-retinol dehydrogenase that has a well-characterized, albeit auxiliary role in the retinoid cycle. Diseases caused by mutations in the RDH11 gene are very rare, and only one affected family with eye and intelligence involvement has been reported. In the present study, we describe the clinical and genetic findings in a Chinese patient with retinitis pigmentosa (RP), juvenile cataracts, intellectual disability, and myopathy. Trio-based whole-exome sequencing and whole genomic copy number variation detection were performed in this family, and compound heterozygous mutations were identified in RDH11 of the patient: c.938T>C (p.Leu313Pro) derived from the father and c.75-3C>A derived from the mother. Variant c.75-3C>A was confirmed to be a splice-site mutation by cDNA sequencing. It caused exon 2 skipping, resulting in a frameshift mutation and premature translation termination (p.Lys26Serfs*38). Moreover, we found mislocalization of RDH11 protein in muscle cells of the patient by using immunofluorescence staining. This is the first case reported in the Chinese population harboring mutations in RDH11 and revealing a new phenotype of syndromic RP with myopathy.

Accurate annotation of human protein-coding small open reading frames.

Functional protein-coding small open reading frames (smORFs) are emerging as an important class of genes. However, the number of translated smORFs in the human genome is unclear because proteogenomic methods are not sensitive enough, and, as we show, Ribo-seq strategies require additional measures to ensure comprehensive and accurate smORF annotation. Here, we integrate de novo transcriptome assembly and Ribo-seq into an improved workflow that overcomes obstacles with previous methods, to more confidently annotate thousands of smORFs. Evolutionary conservation analyses suggest that hundreds of smORF-encoded microproteins are likely functional. Additionally, many smORFs are regulated during fundamental biological processes, such as cell stress. Peptides derived from smORFs are also detectable on human leukocyte antigen complexes, revealing smORFs as a source of antigens. Thus, by including additional validation into our smORF annotation workflow, we accurately identify thousands of unannotated translated smORFs that will provide a rich pool of unexplored, functional human genes.

Room-temperature nanojoining of silver nanowires by graphene oxide for highly conductive flexible transparent electrodes.

Flexible transparent electrodes for touch panels, solar cells, and wearable electronics are in great demand in recent years, and the silver nanowire (AgNW) flexible transparent electrode (FTE) is among the top candidates due to its excellent light transmittance and flexibility and the highest conductivity of silver among all metals. However, the conductivity of an AgNWs network has long been limited by the large contact resistance. Here we show a room-temperature solution process to tackle the challenge by nanojoining AgNWs with two-dimensional graphene oxide (GO). The conductivity of the AgNWs network is improved 18 times due to the enhanced junctions between AgNWs by the coated GOs, and the AgNW-GO FTE exhibits a low sheet resistance of 23 Ohm sq-1and 88% light transmittance. It is stable under high temperature and current and their flexibility is intact after 1000 cycles of bending. Measurements of a bifunctional electrochromic device shows the high performance of the AgNW-GO FTE as a FTE.

Diverse roles of assembly factors revealed by structures of late nuclear pre-60S ribosomes.

Ribosome biogenesis is a highly complex process in eukaryotes, involving temporally and spatially regulated ribosomal protein (r-protein) binding and ribosomal RNA remodelling events in the nucleolus, nucleoplasm and cytoplasm. Hundreds of assembly factors, organized into sequential functional groups, facilitate and guide the maturation process into productive assembly branches in and across different cellular compartments. However, the precise mechanisms by which these assembly factors function are largely unknown. Here we use cryo-electron microscopy to characterize the structures of yeast nucleoplasmic pre-60S particles affinity-purified using the epitope-tagged assembly factor Nog2. Our data pinpoint the locations and determine the structures of over 20 assembly factors, which are enriched in two areas: an arc region extending from the central protuberance to the polypeptide tunnel exit, and the domain including the internal transcribed spacer 2 (ITS2) that separates 5.8S and 25S ribosomal RNAs. In particular, two regulatory GTPases, Nog2 and Nog1, act as hub proteins to interact with multiple, distant assembly factors and functional ribosomal RNA elements, manifesting their critical roles in structural remodelling checkpoints and nuclear export. Moreover, our snapshots of compositionally and structurally different pre-60S intermediates provide essential mechanistic details for three major remodelling events before nuclear export: rotation of the 5S ribonucleoprotein, construction of the active centre and ITS2 removal. The rich structural information in our structures provides a framework to dissect molecular roles of diverse assembly factors in eukaryotic ribosome assembly.