Assembly Factor Research Articles

KU70 and CAF-1 in Arabidopsis: Divergent roles in rDNA stability and telomere homeostasis.

Deficiency in chromatin assembly factor-1 (CAF-1) in plants through dysfunction of its components, FASCIATA1 and 2 (FAS1, FAS2), leads to the specific and progressive loss of rDNA and telomere repeats in plants. This loss is attributed to defective repair mechanisms for the increased DNA breaks encountered during replication, a consequence of impaired replication-dependent chromatin assembly. In this study, we explore the role of KU70 in these processes. Our findings reveal that, although the rDNA copy number is reduced in ku70 mutants when compared with wild-type plants, it is not markedly affected by diverse KU70 status in fas1 mutants. This is consistent with our previous characterisation of rDNA loss in fas mutants as a consequence part of the single-strand annealing pathway of homology-dependent repair. In stark contrast to rDNA, KU70 dysfunction fully suppresses the loss of telomeres in fas1 plants and converts telomeres to their elongated and heterogeneous state typical for ku70 plants. We conclude that the alternative telomere lengthening pathway, known to be activated in the absence of KU70, overrides progressive telomere loss due to CAF-1 dysfunction.

Arp2/3 complex- and formin-mediated actin cytoskeleton networks facilitate actin binding protein sorting in fission yeast

While it is well-established that F-actin networks with specific organizations and dynamics are tightly regulated by distinct sets of associated actin-binding proteins (ABPs), how ABPs self-sort to particular F-actin networks remains largely unclear. We report that actin assembly factors Arp2/3 complex and formin Cdc12 tune the association of ABPs fimbrin Fim1 and tropomyosin Cdc8 to different F-actin networks in fission yeast. Genetic and pharmacological disruption of F-actin networks revealed that Fim1 is preferentially directed to Arp2/3-complex mediated actin patches, whereas Cdc8 is preferentially targeted to formin Cdc12-mediated filaments in the contractile ring. To investigate the role of Arp2/3 complex- and formin Cdc12-mediated actin assembly, we used four-color TIRF microscopy to observe the in vitro reconstitution of ABP sorting with purified proteins. Fim1 or Cdc8 alone bind similarly well to filaments assembled by either assembly factor. However, in ‘competition’ reactions containing both actin assembly factors and both ABPs, ∼2.0-fold more Fim1 and ∼3.5-fold more Cdc8 accumulates on Arp2/3 complex branch points and formin Cdc12-assembled actin filaments, respectively. These findings indicate that F-actin assembly factors Arp2/3 complex and formin Cdc12 help facilitate the recruitment of specific ABPs, thereby tuning ABP sorting and subsequently establishing the identity of F-actin networks in fission yeast.

Assembly and Repair of Photosystem II in Chlamydomonas reinhardtii.

Oxygenic photosynthetic organisms use Photosystem II (PSII) to oxidize water and reduce plastoquinone. Here, we review the mechanisms by which PSII is assembled and turned over in the model green alga Chlamydomonas reinhardtii. This species has been used to make key discoveries in PSII research due to its metabolic flexibility and amenability to genetic approaches. PSII subunits originate from both nuclear and chloroplastic gene products in Chlamydomonas. Nuclear-encoded PSII subunits are transported into the chloroplast and chloroplast-encoded PSII subunits are translated by a coordinated mechanism. Active PSII dimers are built from discrete reaction center complexes in a process facilitated by assembly factors. The phosphorylation of core subunits affects supercomplex formation and localization within the thylakoid network. Proteolysis primarily targets the D1 subunit, which when replaced, allows PSII to be reactivated and completes a repair cycle. While PSII has been extensively studied using Chlamydomonas as a model species, important questions remain about its assembly and repair which are presented here.

Generation of a human induced pluripotent stem cell line NTUHi004-A from a patient with Leigh syndrome harboring a homozygous missense mutation c.836 T > G (p.Met279Arg) in NDUFAF5 gene

Leigh syndrome is a rare autosomal recessive disorder showcasing a diverse range of neurological symptoms. Classical Leigh syndrome is associated with mitochondrial complex I deficiency, primarily resulting from biallelic mutations in the NDUFAF5 gene, encoding the NADH:ubiquinone oxidoreductase complex assembly factor 5. Using the Sendai virus delivery system, we generated an induced pluripotent stem cell line from peripheral blood mononuclear cells of a 47-years-old female patient who carried a homozygous NDUFAF5 c.836 T > G (p.Met279Arg) mutation. This cellular model serves as a tool for investigating the underlying pathogenic mechanisms and for the development of potential treatments for Leigh syndrome.

β-Sitosterol attenuates anlotinib resistance in non-small cell lung cancer cells by inhibiting miR-181a-3p/SHQ1 signaling.

Anlotinib is used for the treatment of advanced non-small cell lung cancer; however, the emergence of drug resistance limits its clinical application. β-sitosterol may also be used to treat lung cancer, but there have been no studies evaluating β-sitosterol against anlotinib-resistant lung cancer. The purpose of this study was to determine the mechanism by which β-sitosterol enhances the sensitivity of lung cancer cells to anlotinib. A549 cells were treated with different concentrations of anlotinib to generate anlotinib-resistant cells (A549/anlotinib cells). miR-181a-3p mimics were transfected into A549/anlotinib cells. A549 and A549/anlotinib cells were treated with β-sitosterol at various concentrations. The Cell Counting Kit-8 (CCK-8) assay was used to measure cell proliferation. Apoptosis was assessed by flow cytometry. Real-time quantitative PCR was used to measure the expression of miR-181a-3p. The interaction of miR-181a-3p with the H/ACA ribonucleoprotein assembly factor (SHQ1) was predicted using the miRDB and TargetScan Human databases and verified with a luciferase reporter assay. The expression of SHQ1, activating transcription factor 6 (ATF6), and glucose-regulated protein 78 (GRP78) were measured by western blot analysis. β-Sitosterol effectively suppressed A549/anlotinib cell proliferation and promoted apoptosis. SHQ1 is a downstream target of miR-181a-3p. The expression of miR-181a-3p was inhibited; however, SHQ1 expression was increased by β-sitosterol treatment of A549/anlotinib cells. The inhibition of SHQ1, ATF6, and GRP78 protein expression by β-sitosterol in A549/anlotinib cells was rescued by increased miR-181a-3p. β-Sitosterol markedly promotes anlotinib-resistant A549 cell apoptosis and inhibits cell proliferation by activating SHQ1/UPR signaling through miR-181a-3p inhibition.

Assembly of Large Flip Chip Die in Ceramic Packages

Hermetic packaging is required to ensure the reliability of processors and application specific integrated circuit (ASIC) chips that are used in strategic systems, whose operating lifetimes typically exceed thirty years. Performance requirements for emerging system applications are dictating the need for one thousand or more I/O, which precludes the use of wire bonded devices. These packaging requirements can be met by flip chip bonding die onto multilayer, high temperature cofired ceramic substrates. The hermetic environment is provided by a Kovar metal ring that is brazed onto the ceramic and sealed in the final assembly step, by welding on a metal cover. Several process and design requirements must be met to achieve high reliability flip chip assemblies. Reflowed devices must be free of flux residues because they are corrosive, provide a path for ion diffusion, are a source of moisture and degrade the adhesion of underfill to chip and substrate. Removal of flux residues by cleaning is problematic because the gap between chip and substrate is very small relative to chip area. A better approach is to bond chips without flux, as we do, by reflowing them in a formic acid environment. An important reliability requirement for strategic hardware is the ability to sustain many cycles over extended temperature ranges. Temperature cycles induce plastic deformation in the solder connections as a result of stresses generated by the mismatch in thermal expansion coefficients of the chip and package. These stresses can be reduced significantly by underfilling the bonded chip with a filled adhesive. Choice of material as well as process execution impact the effectiveness of underfill enhancement of reliability. Optimization of both the physical design and composition of the solder connections is essential to producing reliable flip chip assemblies. We make extensive use of finite element analyses (FEA) in which we track the accumulation of plastic strain energy in the solder connections as they are subjected to temperature cycle induced stresses. Good correlations between the energy accumulated per cycle and the number of cycles to failure can be achieved if accurate state models of the solder are used. We have a catalog of Anand models for the solder compositions that we use in our FEA simulations. One of the more challenging aspects of designing high performance flip chip packages is matching the size and pitch of the bond pads on the ceramic with those on the chip. Current devices use 90 micron diameter pads on 200 micron pitch, but newer designs are migrating towards 80 micron diameter pads on 180 micron pitch. It challenging to maintain tight tolerances on pad geometries in these higher density packages and to route all the additional signals. Thermal management is also an important component of the package design. Thermal vias and thermally conductive underfills are used to remove heat from the front side of the chip. On the backside of the chip, the gap between chip and cover is minimized and filled with a high thermal conductivity interface material. High fidelity FEA modeling is necessary to ensure that the chip can be adequately cooled in its hermetic environment. This paper discusses the impact of these design and assembly factors on the reliability of high performance, hermetically packaged flip chip assemblies.

Lack of mitochondrial complex I assembly factor NDUFAF2 results in a distinctive infantile-onset brainstem neurodegenerative disease with early lethality

BackgroundCongenital disorders of the mitochondrial respiratory chain are a heterogeneous group of inborn errors of metabolism. Among them, NADH:ubiquinone oxidoreductase (complex I, CI) deficiency is the most common. Biallelic pathogenic variants in NDUFAF2, encoding the nuclear assembly CI factor NDUFAF2, were initially reported to cause progressive encephalopathy beginning in infancy. Since the initial report in 2005, less than a dozen patients with NDUFAF2-related disease have been reported.MethodsClinical, biochemical, and neuroradiological features of four new patients residing in Northern Israel were collected during 2016–2022 at Emek Medical Center. Enzymatic activities of the five respiratory-chain complexes were determined in isolated fibroblast mitochondria by spectrophotometric methods. Western blot analyses were conducted with anti-human NDUFAF2 antibody; antibody against the mitochondrial marker VDAC1 was used as a loading control. Genetic studies were performed by chromosome microarray analysis using Affymetrix CytoScan 750 K arrays.ResultsAll four patients presented with infantile-onset growth retardation, ophthalmological impairments with nystagmus, strabismus (starting between 5 and 9 months), and further progressed to life-threatening episodes of apnea usually triggered by trivial febrile illnesses (between 10 and 18 months) with gradual loss of acquired developmental milestones (3 of 4 patients). Serial magnetic-resonance imaging studies in two of the four patients showed a progressive pattern of abnormal T2-weighted hyperintense signals involving primarily the brainstem, the upper cervical cord, and later, the basal ganglia and thalami. Magnetic-resonance spectroscopy in one patient showed an increased lactate peak. Disease progression was marked by ventilatory dependency and early lethality. 3 of the 4 patients tested, harbored a homozygous 142-kb partial interstitial deletion that omits exons 2–4 of NDUFAF2. Mitochondrial CI activity was significantly decreased in the only patient tested. Western blot analysis disclosed the absence of NDUFAF2 protein compared to normal controls. In addition, we reviewed all 10 previously reported NDUFAF2-deficient cases to better characterize the disease.ConclusionsBiallelic loss-of-function mutations in NDUFAF2 result in a distinctive phenotype in the spectrum of Leigh syndrome with clinical and neuroradiological features that are primarily attributed to progressive brainstem damage.

PMF-seq: a highly scalable screening strategy for linking genetics to mitochondrial bioenergetics

Our current understanding of mitochondrial organelle physiology has benefited from two broad approaches: classically, cuvette-based measurements with suspensions of isolated mitochondria, in which bioenergetic parameters are monitored acutely in response to respiratory chain substrates and inhibitors1–4, and more recently, highly scalable genetic screens for fitness phenotypes associated with coarse-grained properties of the mitochondrial state5–10. Here we introduce permeabilized-cell mitochondrial function sequencing (PMF-seq) to combine strengths of these two approaches to connect genes to detailed bioenergetic phenotypes. In PMF-seq, the plasma membranes within a pool of CRISPR mutagenized cells are gently permeabilized under conditions that preserve mitochondrial physiology, where detailed bioenergetics can be probed in the same way as with isolated organelles. Cells with desired bioenergetic parameters are selected optically using flow cytometry and subjected to next-generation sequencing. Using PMF-seq, we recover genes differentially required for mitochondrial respiratory chain branching and reversibility. We demonstrate that human d-lactate dehydrogenase specifically conveys electrons from d-lactate into cytochrome c to support mitochondrial membrane polarization. Finally, we screen for genetic modifiers of tBID, a pro-apoptotic protein that acts directly and acutely on mitochondria. We find the loss of the complex V assembly factor ATPAF2 acts as a genetic sensitizer of tBID’s acute action. We anticipate that PMF-seq will be valuable for defining genes critical to the physiology of mitochondria and other organelles.

Pan-cancer analysis reveals potential immunological and prognostic roles of COA6 in human cancers and preliminary exploration of COA6 in bladder cancer

BackgroundCytochrome C oxidase assembly factor 6 (COA6) is significantly involved in the progression of cancer and is aberrantly expressed in disease. Nevertheless, the comprehensive analysis of COA6 using many omics techniques, and its impact on the prognosis and immunological microenvironment of cancer patients, remains unexplored. MethodsWe gathered data from 33 cancer cases and conducted a thorough analysis of abnormalities in COA6 gene expression. This analysis included examining its relevance to disease, its diagnostic and prognostic value, pathway enrichment, the immune microenvironment, its association with immune checkpoints, and its ability to predict patient response to immunotherapy and natural small molecule drugs that target the COA6 protein. Ultimately, we examined the function of COA6 in bladder cancer by in vitro research. ResultsOur study revealed significant variations in gene expression and identified COA6 as a potential diagnostic biomarker for cancer. COA6 was also discovered to have a crucial function in pan-cancer involving the tumor microenvironment. COA6 has a strong correlation with well-known immunological checkpoints, including TMB and MSI. Molecular docking identified natural small chemical inhibitors that specifically target the COA6 protein. Ultimately, scientific evidence has verified that suppressing the expression of the COA6 gene hinders the growth and infiltration of bladder cancer cells. ConclusionsOur study emphasizes the significant potential of COA6 as a predictive and immunotherapeutic response biomarker. This finding may lead to future investigation into the mechanism of tumor infiltration and the therapeutic possibilities of COA6 in cancer.

CO-EXPRESSED WITH PSI ASSEMBLY1 (CEPA1) is a photosystem I assembly factor in Arabidopsis.

Photosystem I (PSI) forms a large macromolecular complex of ∼580 kDa that resides in the thylakoid membrane and mediates photosynthetic electron transfer. PSI is composed of 18 protein subunits and nearly 200 co-factors. The assembly of the complex in thylakoid membranes requires high spatial and temporal coordination, and is critically dependent on a sophisticated assembly machinery. Here, we report and characterize CO-EXPRESSED WITH PSI ASSEMBLY1 (CEPA1), a PSI assembly factor in Arabidopsis (Arabidopsis thaliana). The CEPA1 gene was identified bioinformatically as being co-expressed with known PSI assembly factors. Disruption of the CEPA1 gene leads to a pale phenotype and retarded plant development but does not entirely abolish photoautotrophy. Biophysical and biochemical analyses revealed that the phenotype is caused by a specific defect in PSI accumulation. We further show that CEPA1 acts at the post-translational level and co-localizes with PSI in nonappressed thylakoid membranes. In native gels, CEPA1 co-migrates with thylakoid protein complexes, including putative PSI assembly intermediates. Finally, protein-protein interaction assays suggest cooperation of CEPA1 with the PSI assembly factor PHOTOSYSTEM I ASSEMBLY3 (PSA3). Together, our data support an important but nonessential role of CEPA1 in PSI assembly.

Age-related changes in human skeletal muscle transcriptome and proteome are more affected by chronic inflammation and physical inactivity than primary aging.

Evaluation of the influence of primary and secondary aging on the manifestation of molecular and cellular hallmarks of aging is a challenging and currently unresolved issue. Our study represents the first demonstration of the distinct role of primary aging and chronic inflammation/physical inactivity - the most important drivers of secondary aging, in the regulation of transcriptomic and proteomic profiles in human skeletal muscle. To achieve this purpose, young healthy people (n = 15), young (n = 8) and older (n = 37) patients with knee/hip osteoarthritis, a model to study the effect of long-term inactivity and chronic inflammation on the vastus lateralis muscle, were included in the study. It was revealed that widespread and substantial age-related changes in gene expression in older patients relative to young healthy people (~4000 genes regulating mitochondrial function, proteostasis, cell membrane, secretory and immune response) were related to the long-term physical inactivity and chronic inflammation rather than primary aging. Primary aging contributed mainly to the regulation of genes (~200) encoding nuclear proteins (regulators of DNA repair, RNA processing, and transcription), mitochondrial proteins (genes encoding respiratory enzymes, mitochondrial complex assembly factors, regulators of cristae formation and mitochondrial reactive oxygen species production), as well as regulators of proteostasis. It was found that proteins associated with aging were regulated mainly at the post-transcriptional level. The set of putative primary aging genes and their potential transcriptional regulators can be used as a resource for further targeted studies investigating the role of individual genes and related transcription factors in the emergence of a senescent cell phenotype.

Using cryo-EM to understand the assembly pathway of respiratory complex I.

Complex I (proton-pumping NADH:ubiquinone oxidoreductase) is the first component of the mitochondrial respiratory chain. In recent years, high-resolution cryo-EM studies of complex I from various species have greatly enhanced the understanding of the structure and function of this important membrane-protein complex. Less well studied is the structural basis of complex I biogenesis. The assembly of this complex of more than 40 subunits, encoded by nuclear or mitochondrial DNA, is an intricate process that requires at least 20 different assembly factors in humans. These are proteins that are transiently associated with building blocks of the complex and are involved in the assembly process, but are not part of mature complex I. Although the assembly pathways have been studied extensively, there is limited information on the structure and molecular function of the assembly factors. Here, the insights that have been gained into the assembly process using cryo-EM are reviewed.

Optic atrophy 1 mediates muscle differentiation by promoting a metabolic switch via the supercomplex assembly factor SCAF1

Optic atrophy 1 mediates muscle differentiation by promoting a metabolic switch via the supercomplex assembly factor SCAF1

SnapShot: Eukaryotic ribosome biogenesis II

Ribosome production is essential for cell growth. Approximately 200 assembly factors drive this complicated pathway that starts in the nucleolus and ends in the cytoplasm. A large number of structural snapshots of the pre-60S pathway have revealed the principles behind large subunit synthesis. To view this SnapShot, open or download the PDF.

Arabidopsis thaliana ubiquitin-associated protein 2 (AtUAP2) functions as an E4 ubiquitin factor and negatively modulates dehydration stress response.

E4, a ubiquitin (Ub) chain assembly factor and post-translational modification protein, plays a key role in the regulation of multiple cellular functions in plants during biotic or abiotic stress. We have more recently reported that E4 factor AtUAP1 is a negative regulator of the osmotic stress response and enhances the multi-Ub chain assembly of E3 ligase Arabidopsis thaliana RING Zinc Finger 1 (AtRZF1). To further investigate the function of other E4 Ub factors in osmotic stress, we isolated AtUAP2, an AtUAP1 homolog, which interacted with AtRZF1, using pull-down assay and bimolecular fluorescence complementation analysis. AtUAP2, a Ub-associated motif-containing protein, interacts with oligo-Ub5, -Ub6, and -Ub7 chains. The yeast functional complementation experiment revealed that AtUAP2 functions as an E4 Ub factor. In addition, AtUAP2 is localized in the cytoplasm, different from AtUAP1. The activity of AtUAP2 was relatively strongly induced in the leaf tissue of AtUAP2 promoter-β-glucuronidase transgenic plants by abscisic acid, dehydration, and oxidative stress. atuap2 RNAi lines were more insensitive to osmotic stress condition than wild-type during the early growth of seedlings, whereas the AtUAP2-overexpressing line exhibited relatively more sensitive responses. Analyses of molecular and physiological experiments showed that AtUAP2 could negatively mediate the osmotic stress-induced signaling. Genetic studies showed that AtRZF1 mutation could suppress the dehydration-induced sensitive phenotype of the AtUAP2-overexpressing line, suggesting that AtRZF1 acts genetically downstream of AtUAP2 during osmotic stress. Taken together, our findings show that the AtRZF1-AtUAP2 complex may play important roles in the ubiquitination pathway, which controls the osmotic stress response in Arabidopsis.

Identification of the key genes and mechanisms associated with transcatheter arterial chemoembolisation refractoriness in hepatocellular carcinoma.

Transcatheter arterial embolisation (TACE) is the primary treatment for intermediate-stage hepatocellular carcinoma (HCC) patients while some HCC cases have shown resistance to TACE. To investigate the key genes and potential mechanisms correlated with TACE refractoriness in HCC. The microarray datasets of TACE-treated HCC tissues, HCC and non-HCC tissues were collected by searching multiple public databases. The respective differentially expressed genes (DEGs) were attained via limma R package. Weighted gene co-expression network analysis was employed for identifying the significant modules related to TACE non-response. TACE refractoriness-related genes were obtained by intersecting up-regulated TACE-associated and HCC-associated DEGs together with the genes in significant modules related to TACE non-response. The key genes expression in the above two pairs of samples was compared respectively via Wilcoxon tests and standard mean differences model. The prognostic value of the key genes was evaluated by Kaplan-Meier curve. Multivariate analysis was utilised to investigate the independent prognostic factor in key genes. Single-cell RNA (scRNA) sequencing analysis was conducted to explore the cell types in HCC. TACE refractoriness-related genes activity was calculated via AUCell packages. The CellChat R package was used for the investigation of the cell-cell communication between the identified cell types. HCC tissues of TACE non-responders (n = 66) and TACE responders (n = 81), HCC (n = 3941) and non-HCC (n = 3443) tissues were obtained. The five key genes, DLG associated protein 5 (DLGAP5), Kinesin family member 20A (KIF20A), Assembly factor for spindle microtubules (ASPM), Kinesin family member 11 (KIF11) and TPX2 microtubule nucleation factor (TPX2) in TACE refractoriness-related genes, were identified. The five key genes were all up-regulated in the TACE non-responders group and the HCC group. High expression of the five key genes predicted poor prognosis in HCC. Among the key genes, TPX2 was an independent prognostic factor. Four cell types, hepatocytes, embryonic stem cells, T cells and B cells, were identified in the HCC tissues. The TACE refractoriness-related genes expressed primarily in hepatocytes and embryonic stem cells. Hepatocytes, as the providers of ligands, had the strongest interaction with embryonic stem cells that provided receptors. Five key genes (DLGAP5, KIF20A, ASPM, KIF11 and TPX2) were identified as promoting refractory TACE. Hepatocytes and embryonic stem cells were likely to boost TACE refractoriness.

Structure of native photosystem II assembly intermediate from Chlamydomonas reinhardtii.

Chlamydomonas reinhardtii Photosystem II (PSII) is a dimer consisting of at least 13 nuclear-encoded and four chloroplast-encoded protein subunits that collectively function as a sunlight-driven oxidoreductase. In this study, we present the inaugural structure of a green alga PSII assembly intermediate (pre-PSII-int). This intermediate was isolated from chloroplast membranes of the temperature-sensitive mutant TSP4, cultivated for 14 hours at a non-permissive temperature. The assembly state comprises a monomer containing subunits A, B, C, D, E, F, H, I, K, and two novel assembly factors, Psb1 and Psb2. Psb1 is identified as a novel transmembrane helix located adjacent to PsbE and PsbF (cytochrome b559). The absence of PsbJ, typically found in mature PSII close to this position, indicates that Psb1 functions as an assembly factor. Psb2 is an eukaryotic homolog of the cyanobacterial assembly factor Psb27. The presence of iron, coupled with the absence of QA, QB, and the manganese cluster, implies a protective mechanism against photodamage and provides insights into the intricate assembly process.

Methylation of ciliary dynein motors involves the essential cytosolic assembly factor DNAAF3/PF22

Axonemal dynein motors drive ciliary motility and can consist of up to twenty distinct components with a combined mass of ~2 MDa. In mammals, failure of dyneins to assemble within the axonemal superstructure leads to primary ciliary dyskinesia. Syndromic phenotypes include infertility, rhinitis, severe bronchial conditions, and situs inversus. Nineteen specific cytosolic factors (Dynein Axonemal Assembly Factors; DNAAFs) are necessary for axonemal dynein assembly, although the detailed mechanisms involved remain very unclear. Here, we identify the essential assembly factor DNAAF3 as a structural ortholog of S-adenosylmethionine-dependent methyltransferases. We demonstrate that dynein heavy chains, especially those forming the ciliary outer arms, are methylated on key residues within various nucleotide-binding sites and on microtubule-binding domain helices directly involved in the transition to low binding affinity. These variable modifications, which are generally missing in a Chlamydomonas null mutant for the DNAAF3 ortholog PF22 (DAB1), likely impact on motor mechanochemistry fine-tuning the activities of individual dynein complexes.

New kid on the photosynthetic block: Ycf51 is a photosystem I assembly factor in cyanobacteria.

New kid on the photosynthetic block: Ycf51 is a photosystem I assembly factor in cyanobacteria.

Testing a Hypothesis of 12S rRNA Methylation by Putative METTL17 Methyltransferase.

Mitochondrial ribosome assembly is a complex multi-step process involving many additional factors. Ribosome formation differs in various groups of organisms. However, there are universal steps of assembly and conservative factors that have been retained in evolutionarily distant taxa. METTL17, the object of the current study, is one of these conservative factors involved in mitochondrial ribosome assembly. It is present in both bacteria and the mitochondria of eukaryotes, in particular mice and humans. In this study, we tested a hypothesis of putative METTL17 methyltransferase activity. MALDI-TOF mass spectrometry was used to evaluate the methylation of a putative METTL17 target - a 12S rRNA region interacting with METTL17 during mitochondrial ribosome assembly. The investigation of METTL17 and other mitochondrial ribosome assembly factors is of both fundamental and practical significance, because defects in mitochondrial ribosome assembly are often associated with human mitochondrial diseases.