Effects of unstable β-PheRS on food avoidance, growth, and development are suppressed by the appetite hormone CCHa2

Amino acyl-tRNA synthetases perform diverse non-canonical functions aside from their essential role in charging tRNAs with their cognate amino acid. The phenylalanyl-tRNA synthetase (PheRS/FARS) is an α2β2 tetramer that is needed for charging the tRNAPhe for its translation activity. Fragments of the α-subunit have been shown to display an additional, translation-independent, function that activates growth and proliferation and counteracts Notch signalling. Here we show in Drosophila that overexpressing the β-subunit in the context of the complete PheRS leads to larval roaming, food avoidance, slow growth, and a developmental delay that can last several days and even prevents pupation. These behavioural and developmental phenotypes are induced by PheRS expression in CCHa2+ and Pros+ cells. Simultaneous expression of β-PheRS, α-PheRS, and the appetite-inducing CCHa2 peptide rescued these phenotypes, linking this β-PheRS activity to the appetite-controlling pathway. The fragmentation dynamic of the excessive β-PheRS points to β-PheRS fragments as possible candidate inducers of these phenotypes. Because fragmentation of human FARS has also been observed in human cells and mutations in human β-PheRS (FARSB) can lead to problems in gaining weight, Drosophila β-PheRS can also serve as a model for the human phenotype and possibly also for obesity.

Ataxia and Hypogonadism: a Review of the Associated Genes and Syndromes

The association of hypogonadism and cerebellar ataxia was first recognized in 1908 by Gordon Holmes. Since the seminal description, several heterogeneous phenotypes have been reported, differing for age at onset, associated features, and gonadotropins levels. In the last decade, the genetic bases of these disorders are being progressively uncovered. Here, we review the diseases associating ataxia and hypogonadism and the corresponding causative genes. In the first part of this study, we focus on clinical syndromes and genes (RNF216, STUB1, PNPLA6, AARS2, SIL1, SETX) predominantly associated with ataxia and hypogonadism as cardinal features. In the second part, we mention clinical syndromes and genes (POLR3A, CLPP, ERAL1, HARS, HSD17B4, LARS2, TWNK, POLG, ATM, WFS1, PMM2, FMR1) linked to complex phenotypes that include, among other features, ataxia and hypogonadism. We propose a diagnostic algorithm for patients with ataxia and hypogonadism, and we discuss the possible common etiopathogenetic mechanisms.

Induction of proteasomal activity in mammalian cells by lifespan-extending tRNA synthetase inhibitors

We have recently shown that multiple tRNA synthetase inhibitors can greatly increase lifespan in multiple models by acting through the conserved transcription factor ATF4. Here, we show that these compounds, and several others of the same class, can greatly upregulate mammalian ATF4 in cells in vitro, in a dose dependent manner. Further, RNASeq analysis of these cells pointed toward changes in protein turnover. In subsequent experiments here we show that multiple tRNA synthetase inhibitors can greatly upregulate activity of the ubiquitin proteasome system (UPS) in cells in an ATF4-dependent manner. The UPS plays an important role in the turnover of many damaged or dysfunctional proteins in an organism. Increasing UPS activity has been shown to enhance the survival of Huntington's disease cell models, but there are few known pharmacological enhancers of the UPS. Additionally, we see separate ATF4 dependent upregulation of macroautophagy upon treatment with tRNA synthetase inhibitors. Protein degradation is an essential cellular process linked to many important human diseases of aging such as Alzheimer's disease and Huntington's disease. These drugs' ability to enhance proteostasis more broadly could have wide-ranging implications in the treatment of important age-related neurodegenerative diseases.

RARS1-related hypomyelinating leukodystrophy-9 (HLD-9) in two distinct Iranian families: Case report and literature review

BACKGROUND

Hypomyelinating leukodystrophy-9 (HLD-9) is caused by biallelic pathogenic variants in RARS1, which codes for the cytoplasmic tRNA synthetase for arginine (ArgRS). This study aims to evaluate the clinical, neuroradiological, and genetic characteristics of patients with RARS1-related disease and determine probable genotype-phenotype relationships.

METHODS

We identified three patients with RARS1 homozygous pathogenic variants. Furthermore, we performed a comprehensive review of the literature.

RESULTS

Homozygous variants of RARS1 (c.2T>C (p.Met1Thr)) were identified in three patients with HLD-9. Clinical symptoms were severe in all patients. Following the literature review, thirty HLD-9 cases from eight studies were found. The 33 patients' main symptoms were hypomyelination, language delay, and intellectual disability or developmental delay. The mean age of onset for HLD9 in the group of 33 patients with a known age of onset was 5.8 months (SD = 8.1). The interquartile range of age of onset was 0-10 months. Of the 25 variants identified, c.5A>G (p.Asp2Gly) was identified in 11 patients.

CONCLUSION

Pathogenic variants in RARS1 decrease ArgRS activity and cause a wide range of symptoms, from severe, early onset epileptic encephalopathy with brain atrophy to a mild condition with relatively maintained myelination. These symptoms include the classic hypomyelination presentation with nystagmus and spasticity. Furthermore, the pathogenicity of the variation c.2T>C (p.Met1Thr) has been shown.

Agreement between local and central anti-synthetase antibodies detection: results from the Classification Criteria of Anti-Synthetase Syndrome project biobank

OBJECTIVES

The CLASS (Classification Criteria of Anti-Synthetase Syndrome) project is a large international multicentre study that aims to create the first data-driven anti-synthetase syndrome (ASSD) classification criteria. Identifying anti-aminoacyl tRNA synthetase antibodies (anti-ARS) is crucial for diagnosis, and several commercial immunoassays are now available for this purpose. However, using these assays risks yielding false-positive or false-negative results, potentially leading to misdiagnosis. The established reference standard for detecting anti-ARS is immunoprecipitation (IP), typically employed in research rather than routine autoantibody testing. We gathered samples from participating centers and results from local anti-ARS testing. As an "ad-interim" study within the CLASS project, we aimed to assess how local immunoassays perform in real-world settings compared to our central definition of anti-ARS positivity.

METHODS

We collected 787 serum samples from participating centres for the CLASS project and their local anti-ARS test results. These samples underwent initial central testing using RNA-IP. Following this, the specificity of ARS was reconfirmed centrally through ELISA, line-blot assay (LIA), and, in cases of conflicting results, protein-IP. The sensitivity, specificity, positive likelihood ratio and positive and negative predictive values were evaluated. We also calculated the inter-rater agreement between central and local results using a weighted κ co-efficient.

RESULTS

Our analysis demonstrates that local, real-world detection of anti-Jo1 is reliable with high sensitivity and specificity with a very good level of agreement with our central definition of anti-Jo1 antibody positivity. However, the agreement between local immunoassay and central determination of anti-non-Jo1 antibodies varied, especially among results obtained using local LIA, ELISA and "other" methods.

CONCLUSIONS

Our study evaluates the performance of real-world identification of anti-synthetase antibodies in a large cohort of multi-national patients with ASSD and controls. Our analysis reinforces the reliability of real-world anti-Jo1 detection methods. In contrast, challenges persist for anti-non-Jo1 identification, particularly anti-PL7 and rarer antibodies such as anti-OJ/KS. Clinicians should exercise caution when interpreting anti-synthetase antibodies, especially when commercial immunoassays test positive for non-anti-Jo1 antibodies.

Differences in muscle magnetic resonance imaging findings between anti-signal recognition particle antibody-positive myopathy and anti-aminoacyl-tRNA synthetase antibody-positive myositis

OBJECTIVES

To compare the findings of muscle magnetic resonance imaging (MRI) between anti-signal recognition particle antibody-positive myopathy (anti-SRP myopathy) and anti-aminoacyl-tRNA synthetase antibody-positive myositis (anti-ARS myositis).

METHODS

Of the patients newly diagnosed with polymyositis (PM)/dermatomyositis (DM) and immune-mediated necrotising myopathy (IMNM) admitted to our Department between April 2012 and December 2021, those who met the eligibility criteria of positive for anti-SRP or anti-ARS antibodies and thigh MRI at the time of diagnosis were included. We compared the lesion sites and MRI findings of the thigh muscles that were classified into oedema, fascial oedema, fatty replacement, and muscle atrophy between the three groups of anti-SRP myopathy, anti-Jo-1 antibody-positive myositis, and non-Jo-1 antibody-positive myositis.

RESULTS

Of the 98 PM/DM and IMNM patients, five anti-SRP myopathy patients and 11 anti-Jo-1-positive and 22 non-Jo-1 antibody-positive patients with myositis were included. The SRP group showed significantly higher blood levels of myogenic enzymes such as serum creatinine kinase (CK) than the other groups (p=0.01). In thigh MRI findings, despite oedema in most cases in anti-SRP and anti-ARS groups, fascial oedema was identified only in the ARS group, frequently in Jo-1 positive patients in particular. Moreover, gluteus maximus muscle lesions occurred more frequently in the SRP group than in the ARS group (p=0.008).

CONCLUSIONS

A comparison of thigh MRI between anti-SRP myopathy and anti-ARS myositis showed different findings and lesion sites reflecting the different pathophysiology that may contribute to their diagnosis.

Prognostic biomarker DARS2 correlated with immune infiltrates in bladder tumor

Background

DARS2 is a pivotal member of the Aminoacyl-tRNA synthetases family that is critical for regulating protein translation. However, the biological role of DARS2 in bladder cancer remains elusive.

Methods

We analyzed the correlation between DARS2 expression and prognosis, tumor stage, and immune infiltration in bladder cancer using The Cancer Genome Atlas (TCGA) database. We validated findings in clinical samples from The First Affiliated Hospital of Nanchang University and explored the biological functions of DARS2 using cell and animal models.

Results

We found DARS2 to be upregulated in bladder cancer, associated with tumor progression and poor prognosis. Immune infiltration analysis suggested that DARS2 may facilitate immune evasion by modulating PD-L1. Cell and animal experiments validated that DARS2 knockdown and overexpress can inhibit or increase cancer cell proliferation, metastasis, tumorigenesis, immune escape, and PD-L1 levels.

Conclusions

Our study reveals DARS2 as a potential prognostic biomarker and immunotherapy target in BLCA.

Tryptophanyl-Transfer RNA Synthetase Is Involved in a Negative Feedback Loop Mitigating Interferon-γ-Induced Gene Expression

Aminoacyl-tRNA synthetases (aaRSs) are essential enzymes responsible for linking a transfer RNA (tRNA) with its cognate amino acid present in all the kingdoms of life. Besides their aminoacyl-tRNA synthetase activity, it was described that many of these enzymes can carry out non-canonical functions. They were shown to be involved in important biological processes such as metabolism, immunity, development, angiogenesis and tumorigenesis. In the present work, we provide evidence that tryptophanyl-tRNA synthetase might be involved in a negative feedback loop mitigating the expression of certain interferon-γ-induced genes. Mining the available TCGA and Gtex data, we found that WARS was highly expressed in cutaneous melanoma (SKCM) compared to other cancers and is of good prognosis for this particular cancer type. WARS expression correlates with genes involved in antigen processing and presentation but also transcription factors involved in IFN-γ signaling such as STAT1. In addition, WARS was found in complex with STAT1 in A375 cells treated with IFN-γ. Finally, we showed that knocking down WARS expression during IFN-γ stimulation further increases the expression of GBP2, APOL1, ISG15, HLA-A and IDO1.

DWN12088, A Prolyl-tRNA Synthetase Inhibitor, Alleviates Hepatic Injury in Nonalcoholic Steatohepatitis

BACKGRUOUND

Nonalcoholic steatohepatitis (NASH) is a liver disease caused by obesity that leads to hepatic lipoapoptosis, resulting in fibrosis and cirrhosis. However, the mechanism underlying NASH is largely unknown, and there is currently no effective therapeutic agent against it. DWN12088, an agent used for treating idiopathic pulmonary fibrosis, is a selective prolyl-tRNA synthetase (PRS) inhibitor that suppresses the synthesis of collagen. However, the mechanism underlying the hepatoprotective effect of DWN12088 is not clear. Therefore, we investigated the role of DWN12088 in NASH progression.

METHODS

Mice were fed a chow diet or methionine-choline deficient (MCD)-diet, which was administered with DWN12088 or saline by oral gavage for 6 weeks. The effects of DWN12088 on NASH were evaluated by pathophysiological examinations, such as real-time quantitative reverse transcription polymerase chain reaction, immunoblotting, biochemical analysis, and immunohistochemistry. Molecular and cellular mechanisms of hepatic injury were assessed by in vitro cell culture.

RESULTS

DWN12088 attenuated palmitic acid (PA)-induced lipid accumulation and lipoapoptosis by downregulating the Rho-kinase (ROCK)/AMP-activated protein kinase (AMPK)/sterol regulatory element-binding protein-1c (SREBP-1c) and protein kinase R-like endoplasmic reticulum kinase (PERK)/α subunit of eukaryotic initiation factor 2 (eIF2α)/activating transcription factor 4 (ATF4)/C/EBP-homologous protein (CHOP) signaling cascades. PA increased but DWN12088 inhibited the phosphorylation of nuclear factor-κB (NF-κB) p65 (Ser536, Ser276) and the expression of proinflammatory genes. Moreover, the DWN12088 inhibited transforming growth factor β (TGFβ)-induced pro-fibrotic gene expression by suppressing TGFβ receptor 1 (TGFβR1)/Smad2/3 and TGFβR1/glutamyl-prolyl-tRNA synthetase (EPRS)/signal transducer and activator of transcription 6 (STAT6) axis signaling. In the case of MCD-diet-induced NASH, DWN12088 reduced hepatic steatosis, inflammation, and lipoapoptosis and prevented the progression of fibrosis.

CONCLUSION

Our findings provide new insights about DWN12088, namely that it plays an important role in the overall improvement of NASH. Hence, DWN12088 shows great potential to be developed as a new integrated therapeutic agent for NASH.

Analytic and Clinical Validity of Myositis-Specific Antibodies by Line-Blot Immunoassay Is Essential

OBJECTIVES

This study assessed the concordance between line blot (LB) and immunoprecipitation (IP) assays for detecting myositis-specific antibodies (MSAs) in idiopathic inflammatory myopathies (IIMs) and their association with IIM subtypes.

METHODS

One hundred patients with IIM were enrolled, and MSA was detected using LB and IP. The IIM subtypes, including immune-mediated necrotizing myopathy-like, anti-tRNA synthetase syndrome-like, and clinically amyopathic dermatomyositis-like, were clinically diagnosed. The validity and reliability of the LB compared with the IP were evaluated. Optimal cutoff levels for LB were determined using various statistical methods including Cohen κ, Gwet's AC, diagnostic odds ratios, and receiver operating characteristic analysis.

RESULTS

Line blot exhibited lower specificity and accuracy than IP in predicting IIM subtypes. Some MSAs performed better at higher LB cutoff values. Anti-signal recognition particle antibodies showed poor performance in predicting the immune-mediated necrotizing myopathy-like subtype using LB. Raising the cutoffs improved the reliability of anti-threonyl-tRNA synthetase and anti-signal recognition particle antibodies. Anti-histidyl-tRNA synthetase antibodies performed well at lower positivity, whereas diagnostic odds ratios increased for anti-transcription intermediary factor 1γ and anti-nuclear matrix protein 2 with higher cutoffs.

CONCLUSIONS

Inconsistencies between LB and IP have been observed in patients with IIM. Individual optimal cutoffs for MSA by LB correlating with IP were determined. Rheumatologists should consider the differences between LB and IP results when classifying IIM subtypes.

[Analysis of perrault syndrome caused by pathogenic variants in LARS2 and HARS2 genes]

Objective: To investigate the molecular etiology of Perrault syndrome by analyzing the clinical phenotype and pathogenic gene variants of 2 male patients with bilateral severe sensorineural deafness. Methods: Two male patients with Perrault syndrome characterized by severe sensonrineual deafness adimitted to the First Affiliated Hospital of Zhengzhou University between February 2021 and March 2022 were selected, and the clinical phenotype and pathogenic gene variants of them and their family members were summarized. The whole exome sequencing technology was used to screen the pathogenic variants of the probands, and the candidate variants were determined by combining with clinical phenotype. The probands and their family members were verified by the Sanger sequencing method. Results: The whole exome sequencing results showed that the proband of family 1 had a compound heterozygous variants of the LARS2 (NM_015340.4) gene c.1565C>A (p.Thr522Asn) and c.1079T>C (p.Ile360Thr). The reported pathogenic variant c.1565C>A came from the mother, and the novel variant c.1079T>C came from the father. The second proband harbored compound heterozygous variants of HARS2 gene (NM_012208.4) c.1273C>T (p.Arg425Trp) and c.1403G>C (p.Gly468Ala), with the former from the proband's mother, the latter from the father. The c.1273C>T was novel and c.1403G>C was the reported pathogenic variant. All above variants were respectively classified as pathogenic, uncertain significance, uncertain significance and likely pathogenic based on the ACMG guidelines. Conclusion: This study expands the mutational spectrum of LARS2 and HARS2 genes, which highlights that genetic testing plays an important role in the early diagnosis of syndromic deafness.

Clinical characteristics and prognostic analysis of idiopathic inflammatory myopathy with positive anti-aminoacyl-tRNA synthetase antibodies: A single center experience

OBJECTIVES

To identify the differences of clinical characteristics, laboratory findings, and the long-term outcomes in patients with anti-synthetase syndrome (ASS) of different anti-aminoacyl-transfer RNA synthetase antibodies.

METHODS

We retrospectively enrolled 119 patients with ASS, and the clinical characteristics and laboratory findings were collected. Additionally, multivariate COX regression analysis was performed to estimate the risk factors of prognosis in patients with ASS.

RESULTS

The frequency of interstitial lung disease (ILD) reached 93.3% in our cohort, of 28 (23.5%) was classified as rapidly progressive (RP)-ILD. The highest incidence of RP-ILD was 36.4% in the PL12 group of ASS patients. The ILD group was characterized by an older age, a lower prevalence of V sign, and a higher prevalence of pulmonary symptoms when contrasted with the non-ILD group. There were statistical differences of clinical significance in arthritis, myositis, mechanic's hands, triad, shawl sign, V sign, and Raynaud's phenomenon among the four subgroups (all p < .05). Additionally, the prevalence rates of arthritis, myositis, mechanic's hands, triad, and V sign in the anti-Jo1 antibody-positive group were significantly higher than anti-Jo1 antibody-negative patients with ASS (all p < .05). Multivariate Cox regression analysis showed mechanic's hands (odds ratio [OR] = 6.47, p < .001), anti-nuclear antibodies (ANA) (OR = 2.13, p = .026), ILD (OR = 10.50, p < .001), and V sign (OR = 0.30, p = .007) were independent factors affecting the prognosis of patients with ASS. The incidences of RP-ILD, arthritis, myositis, triad, mechanic's hands, and shawl sign were more frequent in the anti-Ro52 antibody-positive group than the anti-Ro52 antibody-negative patients with ASS (all p < .05).

CONCLUSIONS

Patients with ASS accompanied with ILD are highly prevalent. Mechanic's hands, ANA, and ILD may be a potential biomarker for predicting a poor prognosis in patients with ASS. Additionally, the detection of the anti-Ro52 antibody provides valuable insights for managing and predicting disease progression and long-term outcomes.

Immune cell profiles of idiopathic inflammatory myopathy patients expressed anti-aminoacyl tRNA synthetase or anti-melanoma differentiation-associated gene 5 autoantibodies

BACKGROUND

Patients with idiopathic inflammatory myopathy (IIM) often express a different type of myositis-specific autoantibodies (MSAs), each associated with different clinical symptoms. Understanding the immunopathogenesis of various IIM subgroups can help improve the diagnosis and prognosis of IIM patients with different MSAs. However, the immune cell profiles of these IIM patients with anti-aminoacyl tRNA synthetase (ARS) or anti-melanoma differentiation-associated gene 5 (MDA5) autoantibodies remain unclear. We focused on the immune cell profiles of IIM patients with anti-ARS or anti-MDA5 autoantibodies.

RESULTS

The peripheral blood from IIM patients with anti-MDA5 autoantibody (MDA5 + group, n = 24) or one of the anti-ARS autoantibodies (ARS + group, n = 40) autoantibodies, and healthy controls (HC group, n = 60) were collected and examined. We found that IIM patients had a lower CD3 T cell population compared to the HC group. IIM patients showed a significantly lower TN cell population and a higher TEMRA cell population. Higher Th17 and Treg cell populations were found in these IIM patients than in the HC group. In these IIM patients, the MDA5 + group exhibited the higher percentages of Th17 and Treg cells than the ARS + group. It is noteworthy that the percentage of Th1 cells in the survival subgroup was higher than in the death subgroup in IIM patients with ARS + or MDA5 + . Furthermore, in the MDA5 + group, the percentage of Treg cells was higher in the survival subgroup compared to the death subgroup.

CONCLUSIONS

Our study demonstrated that elevated Th1 may be a good prognostic indicator in IIM patients with ARS + or MDA5 + . Elevated Treg may also help predict a good prognosis in MDA5 + IIM patients. However, more large-scale studies and clinical samples are needed to verify the significance of Th1 and Treg cell subsets in clinical outcomes for these IIM patients with ARS + or MDA5 + . These data may help design a therapeutic approach that specifically targets the pathogenic immune molecular responsible for autoimmune attacks in IIM.

Mammalian mitochondrial translation infidelity leads to oxidative stress-induced cell cycle arrest and cardiomyopathy

Proofreading (editing) of mischarged tRNAs by cytoplasmic aminoacyl-tRNA synthetases (aaRSs), whose impairment causes neurodegeneration and cardiac diseases, is of high significance for protein homeostasis. However, whether mitochondrial translation needs fidelity and the significance of editing by mitochondrial aaRSs have been unclear. Here, we show that mammalian cells critically depended on the editing of mitochondrial threonyl-tRNA synthetase (mtThrRS, encoded by Tars2), disruption of which accumulated Ser-tRNAThr and generated a large abundance of Thr-to-Ser misincorporated peptides in vivo. Such infidelity impaired mitochondrial translation and oxidative phosphorylation, causing oxidative stress and cell cycle arrest in the G0/G1 phase. Notably, reactive oxygen species (ROS) scavenging by N-acetylcysteine attenuated this abnormal cell proliferation. A mouse model of heart-specific defective mtThrRS editing was established. Increased ROS levels, blocked cardiomyocyte proliferation, contractile dysfunction, dilated cardiomyopathy, and cardiac fibrosis were observed. Our results elucidate that mitochondria critically require a high level of translational accuracy at Thr codons and highlight the cellular dysfunctions and imbalance in tissue homeostasis caused by mitochondrial mistranslation.

Age distribution and prevalence in different age groups of four myositis-specific autoantibodies, including anti-ARS, anti-MDA5, anti-Mi-2, and anti-TIF1γ antibodies

We accumulated the demographic information and analyzed the prevalence of myositis-specific antibodies (MSAs) in a large cohort across Japan as standard testing for MSAs becomes more widely available. This retrospective, observational, cohort study analyzed the records of individuals aged 0-99 years who are tested for serum MSAs at SRL Incorporation from January 2014 to April 2020 across Japan. An enzyme-linked immunosorbent assay testing was applied to determine the presence of anti-aminoacyl tRNA synthetase (anti-ARS), anti-Mi-2, anti-melanoma differentiation-associated gene 5 (anti-MDA5), or anti-transcriptional intermediary factor 1-γ (anti-TIF1γ) (Medical and Biological Laboratories). Anti-TIF1γ antibody was detected more in male patients than female patients. In contrast, women were predominant in patients with other MSAs. More than half of the anti-ARS or anti-TIF1γ antibody-positive patients were over 60 years old, although anti-MDA5 or anti-Mi-2-positive patients were mostly under <60 years old. Anti-MDA5 antibody-positive patients were mostly aged 40-59 years, while other MSA groups were mostly 60-79 years. Anti-MDA5 antibody was detected most frequently in the age range of 0-29 years. Anti-TIF1γ antibody was the second most commonly detected autoantibody in the age range of 0-19 years. Anti-ARS antibody was the most frequently detected autoantibody after the age of 30 years, and the frequency of anti-ARS gradually increased at more advanced ages. The second and third most detected autoantibodies were anti-MDA5 and anti-TIF1γ, respectively, in ages 30-79 years. We performed a nationwide >3-year evaluation of MSA detection in a routine diagnostic setting. This paper provides clinical images concerning the relationship between four MSA types and the distribution of sex and age in a large population.

DS86760016, a Leucyl-tRNA Synthetase Inhibitor, Is Active against Mycobacterium abscessus

Benzoxaboroles are a new class of leucyl-tRNA synthetase inhibitors. Epetraborole, a benzoxaborole, is a clinical candidate developed for Gram-negative infections and has been confirmed to exhibit favorable activity against a well known pulmonary pathogen, Mycobacterium abscessus. However, according to ClinicalTrials.gov, in 2017, a clinical phase II study on the use of epetraborole to treat complicated urinary tract and intra-abdominal infections was terminated due to the rapid emergence of drug resistance during treatment. Nevertheless, epetraborole is in clinical development for nontuberculous mycobacteria (NTM) disease especially for Mycobacterium avium complex-related pulmonary disease (MAC-PD). DS86760016, an epetraborole analog, was further demonstrated to have an improved pharmacokinetic profile, lower plasma clearance, longer plasma half-life, and higher renal excretion than epetraborole in animal models. In this study, DS86760016 was found to be similarly active against M. abscessus in vitro, intracellularly, and in zebrafish infection models with a low mutation frequency. These results expand the diversity of druggable compounds as new benzoxaborole-based candidates for treating M. abscessus diseases.

Tofacitinib treatment in anti-glycyl-tRNA synthetase antibody interstitial lung disease - A case report

Anti-aminoacyl-transfer-RNA synthetase syndrome (ASS) related interstitial lung disease (ILD) is rarely presented initially alongside acute respiratory distress syndrome (ARDS), which in and of itself is a severe condition with a high mortality rate. Additionally, rapidly progressive change is not a common feature in ASS. Numerous case reports have described the efficacy which tofacitinib has on rapidly progressive ILD (RP-ILD). However, none have mentioned the use of tofacitinib in patients with impaired renal function. Herein, a case of ASS involving ILD is reported with the initial presentation of RP-ILD to ARDS being complicated by acute renal failure with an initial complete response to tofacitinib. Patients experiencing unexplained rapidly progressive interstitial pneumonia should be examined thoroughly for the diagnosis of ASS. Furthermore, tofacitinib can also be considered as a choice of treatment even in patients with impaired renal function.

Comprehensive Characterization of RNA-Binding Proteins in Colon Adenocarcinoma Identifies a Novel Prognostic Signature for Predicting Clinical Outcomes and Immunotherapy Responses Based on Machine Learning

BACKGROUND

RNA-binding proteins (RBPs) are crucial factors that function in the posttranscriptional modification process and are significant in cancer.

OBJECTIVE

This research aimed for a multigene signature to predict the prognosis and immunotherapy response of patients with colon adenocarcinoma (COAD) based on the expression profile of RNA-binding proteins (RBPs).

METHODS

COAD samples retrieved from the TCGA and GEO datasets were utilized for a training dataset and a validation dataset. Totally, 14 shared RBP genes with prognostic significance were identified. Non-negative matrix factorization clusters defined by these RBPs could stratify COAD patients into two molecular subtypes. Cox regression analysis and identification of 8-gene signature categorized COAD patients into high- and low-risk populations with significantly different prognosis and immunotherapy responses.

RESULTS

Our prediction signature was superior to another five well-established prediction models. A nomogram was generated to quantificationally predict the overall survival (OS) rate, validated by calibration curves. Our findings also indicated that high-risk populations possessed an enhanced immune evasion capacity and low-risk populations might benefit immunotherapy, especially for the joint combination of PD-1 and CTLA4 immunosuppressants. DHX15 and LARS2 were detected with significantly different expressions in both datasets, which were further confirmed by qRTPCR and immunohistochemical staining.

CONCLUSION

Our observations supported an eight-RBP-related signature that could be applied for survival prediction and immunotherapy response of patients with COAD.

Fulminant Respiratory Failure Caused by Anti-asparaginyl tRNA Synthetase (Anti-KS) Antibody Syndrome-related Interstitial Lung Disease

Anti-asparaginyl transfer RNA (tRNA) synthetase (KS) antibodies, detected in <5% patients with anti-aminoacyl-tRNA synthetase antibody syndrome, are strongly associated with interstitial pneumonia but not myositis and skin symptoms. A recent report suggested that most patients with interstitial pneumonia and anti-KS antibody (KS-ILD) may present with chronic disease. We herein report a rare case of severe acute respiratory failure in a KS-ILD patient requiring extracorporeal membrane oxygenation (ECMO). ECMO is useful for facilitating not only lung rest until recovery but also the definitive diagnosis and treatment of ILD. KS-ILD can develop acutely with fulminant respiratory failure, as observed in this case.

Unilateral Autoimmune Pulmonary Alveolar Proteinosis with Polymyositis-related Interstitial Lung Disease

A 61-year-old patient with cystic bronchiectasis and bronchial artery hyperplasia in the left lung was diagnosed with polymyositis-related interstitial lung disease. After nine months of immunosuppressive therapy, he developed unilateral autoimmune pulmonary alveolar proteinosis (APAP) in the right lung with respiratory failure. After bronchial artery embolization to prevent massive hemoptysis, whole-lung lavage was performed using veno-venous extracorporeal membrane oxygenation. His respiratory condition improved, and he was discharged from the hospital with supplemental oxygen. Three reported cases of APAP with polymyositis-related interstitial lung disease, including the present case, were all positive for anti-glycyl tRNA synthetase antibody and were under immunosuppressive treatment.

The clinical features and prognoses of anti-MDA5 and anti-aminoacyl-tRNA synthetase antibody double-positive dermatomyositis patients

Objective

To explore the clinical features and prognoses of dermatomyositis (DM) associated with a double-positive anti-MDA5 and anti-aminoacyl-tRNA synthetase (anti-ARS) antibody presentation.

Methods

We retrospectively analyzed 1280 consecutive patients with idiopathic inflammatory myopathy (IIM). Individuals with anti-MDA5 and anti-ARS antibodies (anti-MDA5+/ARS+) were compared to anti-MDA5-/ARS+ and anti-MDA5+/ARS- control individuals based on clinical, pulmonary radiological characteristics, treatment, and follow-up information.

Results

Six individuals (0.47%) presented with anti-MDA5+/ARS+; of these, 2 (33.3%) were anti-PL-12+, 2 (33.3%) were anti-Jo-1+, 1 (16.7%) was anti-EJ+, and 1 (16.7%) was anti-PL-7+. Hallmark cutaneous manifestations, including Gottron’s sign (100%), heliotrope rash (50%), mechanic’s hand (66.7%), and skin ulcers (16.7%) were common. Anti-MDA5+/ARS+ patients tended to have higher ferritin levels (p = 0.038) than anti-MDA5-/ARS+ group, and higher CD4+ T-cell counts (p = 0.032) compared to the anti-MDA5+/ARS- group. Radiologically, NSIP with OP overlap was predominant (60%). Consolidation (60%), ground-glass attenuation (GGA) (80%), traction bronchiectasis (80%), and intralobular reticulation (100%) were common in anti-MDA5+/ARS+ individuals. All were diagnosed with ILD and 50% were categorized as RPILD. All patients received glucocorticoids combined with one or more immunosuppressants. Most (83.3%) had a good prognosis following treatment, but there was no difference in the survival rate between the three subgroups.

Conclusion

Presentation with anti-MDA5+/ARS+ DM was rare. The clinical and radiological characteristics of anti-MDA5+/ARS+ DM combined the features of anti-MDA5+ and anti-ARS+ individuals. Individuals with anti-MDA5+/ARS+ antibodies may respond well to glucocorticoid therapy; glucocorticoids combined with one or more immunosuppressants may be considered a basic treatment approach.

Discovery of benzodioxane analogues as lead candidates of AIMP2-DX2 inhibitors

Aminoacyl-tRNA synthetase (ARS) interacting multifunctional protein2 (AIMP2) plays a vital role in protein synthesis. However, a splicing variant in which the second of the four exons of AIMP2 is deleted, inhibits the tumor suppression activity of AIMP2. Herein, we describe our discovery of series of potent AIMP2-DX2 inhibitors that are targeting lung cancer. Optimization of series using ligand-based drug design strategy led to discovery of compound 35, a potent AIMP2-DX2 inhibitor that is the most efficacious in H460 and A549 cells. This benzodioxane series may represent good starting points for further lead optimization of the identification potential drug candidates for the AIMP2-DX2 targeted treatment of lung cancer.

Dermatomyositis Which Was Double Positive for Anti-MDA5 and Anti-ARS Antibodies That Was Successfully Treated by Intensive Immunosuppressive Therapy

Myositis-specific autoantibody is associated with the clinical phenotype and prognosis of dermatomyositis. Anti-melanoma differentiation-associated gene 5 (MDA5) and anti-aminoacyl-tRNA synthetase (ARS) antibodies are generally mutually exclusive. We herein present an extremely rare case of dermatomyositis which showed double positivity for anti-MDA5 and anti-ARS antibodies. There have been very few reported cases of double positive anti-MDA5, anti-ARS antibodies. In such cases, the clinical characteristics of each autoantibody can coexist. Thus, we should pay attention to the rapidly progressing features of anti-MDA5 as well as the chronic relapsing features of anti-ARS for the better management of this rare condition.

Genetics of ovarian insufficiency and defects of folliculogenesis

Primary ovarian insufficiency (POI) is determined by exhaustion of follicles in the ovaries, which leads to infertility before the age of 40 years. It is characterized by a strong familial and heterogeneous genetic background. Therefore, we will mainly discuss the genetic basis of POI in this review. We identified 107 genes related to POI etiology in mammals described by several independent groups. Thirty-four of these genes (AARS2, AIRE, ANTXR1, ATM, BMPR1B, CLPP, CYP17A1, CYP19A1, DCAF17, EIF2B, ERAL1, FANCA, FANCC, FMR1, FOXL2, GALT, GNAS, HARS2, HSD17B4, LARS2, LMNA, MGME1, NBN, PMM2, POLG, PREPL, RCBTB1, RECQL2/3/4, STAR, TWNK, and XRCC4/9) have been linked to syndromic POI and are mainly implicated in metabolism function and meiosis/DNA repair. In addition, the majority of genes associated with nonsyndromic POI, widely expanded by high-throughput techniques over the last decade, have been implicated in ovarian development and meiosis/DNA repair pathways (ATG7, ATG9, ANKRD31, BMP8B, BMP15, BMPR1A, BMPR1B, BMPR2, BNC1, BRCA2, CPEB1, C14ORF39, DAZL, DIAPH2, DMC1, ERCC6, FANCL, FANCM, FIGLA, FSHR, GATA4, GDF9, GJA4, HELQ, HSF2BP, HFM1, INSL3, LHCGR, LHX8, MCM8, MCM9, MEIOB, MSH4, MSH5, NANOS3, NOBOX, NOTCH2, NR5A1, NUP107, PGRMC1, POLR3H, PRDM1, PRDM9, PSMC3IP, SOHLH1, SOHLH2, SPIDR, STAG3, SYCE1, TP63, UBR2, WDR62, and XRCC2), whereas a few are related to metabolic functions (EIF4ENIF1, KHDRBS1, MRPS22, POLR2C). Some genes, such as STRA8, FOXO3A, KIT, KITL, WNT4, and FANCE, have been shown to cause ovarian insufficiency in rodents, but mutations in these genes have yet to be elucidated in women affected by POI. Lastly, some genes have been rarely implicated in its etiology (AMH, AMHR2, ERRC2, ESR1, INHA, LMN4, POF1B, POU5F1, REC8, SMC1B). Considering the heterogeneous genetic and familial background of this disorder, we hope that an overview of literature data would reinforce that genetic screening of those patients is worthwhile and helpful for better genetic counseling and patient management.

Genetic Incorporation of ϵ-N-Benzoyllysine by Engineering Methanomethylophilus alvus Pyrrolysyl-tRNA Synthetase

Post-translational modifications regulate protein structure and function. Lysine benzoylation is a newly discovered histone modification with unique physiological relevance. To construct proteins with this modification site-specifically, we generated orthogonal tRNAPyl -MaBzKRS pairs by engineering Methanomethylophilus alvus pyrrolysyl-tRNA synthetase, allowing the genetic incorporation of ϵ-N-benzoyllysine (BzK) into proteins with high efficiency in E. coli and mammalian cells. Two types of MaBzKRS were identified to incorporate BzK using mutations located at different positions of the amino acid binding pocket. These MaBzKRS are small in size and highly expressed, which will afford broad utilities in studying the biological effects of lysine benzoylation.

High-Resolution CT Findings of Myositis-Related Interstitial Lung Disease

Myositis-related interstitial lung disease presents with a wide variety of lesions, ranging from chronic to acute. It can be divided into two main forms by the types of onsets, namely, chronic to subacute type showing nonspecific interstitial pneumonia (NSIP) or NSIP with an organizing pneumonia (OP)/fibrosing OP (FOP) pattern and acute type showing acute lung injury (ALI) to diffuse alveolar damage (DAD) pattern. Anti-aminoacyl tRNA Synthetase antibody-positive cases mainly show an NSIP or FOP pattern, whereas anti-melanoma differentiation-associated gene 5 antibody-positive cases show ALI to DAD pattern. Bilateral consolidation with or without ground-glass opacification with lower lobe predominance is common as a major pattern in all types, but the distribution or extent is sometimes different. The early detection of findings that indicate a rapid progressive course is vital. Diffuse cranio-caudal distribution and multiple ground-glass opacifications with random distribution might indicate a poorer prognosis.

Premature live birth in a woman with antisynthetase syndrome following recurrent miscarriages

Antisynthetase syndrome (anti-SS) is a rare systemic autoimmune disease characterised by autoantibodies against aminoacyl-tRNA synthetases manifesting as one or more components of the classic triad: interstitial lung disease, arthritis and myositis. While it is well-recognised that autoimmune rheumatological disorders in general can contribute to multiple pregnancy complications, very little is known about how anti-SS itself affects pregnancy outcomes. Described here is the case of a 26-year-old pregnant woman with anti-SS whose pregnancy course was complicated by placental dysfunction and subsequent extremely premature delivery at 24 weeks' gestation. This report presents a review of the literature to date and discusses potential pregnancy complications associated with anti-SS and their subsequent targeted management.

Impedance Matching and the Choice Between Alternative Pathways for the Origin of Genetic Coding

We recently observed that errors in gene replication and translation could be seen qualitatively to behave analogously to the impedances in acoustical and electronic energy transducing systems. We develop here quantitative relationships necessary to confirm that analogy and to place it into the context of the minimization of dissipative losses of both chemical free energy and information. The formal developments include expressions for the information transferred from a template to a new polymer, Iσ; an impedance parameter, Z; and an effective alphabet size, neff; all of which have non-linear dependences on the fidelity parameter, q, and the alphabet size, n. Surfaces of these functions over the {n,q} plane reveal key new insights into the origin of coding. Our conclusion is that the emergence and evolutionary refinement of information transfer in biology follow principles previously identified to govern physical energy flows, strengthening analogies (i) between chemical self-organization and biological natural selection, and (ii) between the course of evolutionary trajectories and the most probable pathways for time-dependent transitions in physics. Matching the informational impedance of translation to the four-letter alphabet of genes uncovers a pivotal role for the redundancy of triplet codons in preserving as much intrinsic genetic information as possible, especially in early stages when the coding alphabet size was small.

Glucose Starvation Blocks Translation at Multiple Levels

Deficiency of glucose, even under sufficient amino acid supply, turns off translation and promotes catabolic processes to aid cell survival. A recent report by Yoon et al. (2020) shows that glucose is required for the full activity of the leucyl-tRNA synthetase LARS1 and maintains mTORC1 function via LARS1 to enhance translation. Glucose starvation abolishes both effects via phosphorylation of LARS1 by the AMPK-ULK1 signaling pathway. This study supports the idea that glucose starvation inhibits translation at multiple levels.

Expanding the limits of the second genetic code with ribozymes

The site-specific incorporation of noncanonical monomers into polypeptides through genetic code reprogramming permits synthesis of bio-based products that extend beyond natural limits. To better enable such efforts, flexizymes (transfer RNA (tRNA) synthetase-like ribozymes that recognize synthetic leaving groups) have been used to expand the scope of chemical substrates for ribosome-directed polymerization. The development of design rules for flexizyme-catalyzed acylation should allow scalable and rational expansion of genetic code reprogramming. Here we report the systematic synthesis of 37 substrates based on 4 chemically diverse scaffolds (phenylalanine, benzoic acid, heteroaromatic, and aliphatic monomers) with different electronic and steric factors. Of these substrates, 32 were acylated onto tRNA and incorporated into peptides by in vitro translation. Based on the design rules derived from this expanded alphabet, we successfully predicted the acylation of 6 additional monomers that could uniquely be incorporated into peptides and direct N-terminal incorporation of an aldehyde group for orthogonal bioconjugation reactions.

A Weak Spot in Multiple Protozoan Parasites

Eukaryotic protozoan parasites, including the etiological agents of malaria, toxoplasmosis, and leishmaniasis, collectively cause significant mortality in humans. In a recent issue of Structure,Jain et al. (2017) identify a set of quinazolinone-based derivatives targeting the parasitic prolyl-tRNA synthetase enzyme as promising drugs for the clearance of diverse parasites.

Not your usual tRNA synthetase: hWARS serves as an enterovirus entry factor

Enteroviruses, including subtype EV-A71, infect the brain, liver, heart, and other organs, causing a myriad of human diseases. This spectrum of disease is thought to be due, in part, to differential binding to host cells, and additional knowledge of enterovirus cell entry is essential for therapeutic development. In this issue of the JCI, Yeung et al. provide evidence of a novel EV-A71 entry factor, a host-produced tryptophan tRNA synthetase (hWARS), that facilitates entry of multiple subtypes of enteroviruses. hWARS is a cytoplasmic enzyme that is essential for translation but also upregulated and secreted during inflammatory processes. The results of this study support the notion of secreted hWARS as an unconventional virus entry factor that raises interesting questions about mechanisms by which inflammation and a tRNA synthetase facilitate viral pathogenesis.

Lentiviral vector-mediated shRNA against AIMP2-DX2 suppresses lung cancer cell growth through blocking glucose uptake

Aminoacyl-tRNA synthetases [ARS]-interacting multifunctional protein 2 (AIMP2) has been implicated in the control of cell fate and lung cell differentiation. A variant of AIMP2 lacking exon 2 (AIMP2-DX2) is expressed in different cancer cells. We previously studied the expression level of AIMP2-DX2 in several lung cell lines and reported elevated expression levels of AIMP2-DX2 in NCI-H460 and NCI-H520. Here, we report that the suppression of AIMP2-DX2 by lentivirus mediated short hairpin (sh)RNA (sh-DX2) decreased the rate of glucose uptake and glucose transporters (Gluts) in NCI-H460 cells. Down-regulation of AIMP2-DX2 reduced glycosyltransferase (GnT)-V in the Golgi apparatus, while inducing the GnT-V antagonist GnT-III. Down-regulation of AIMP2-DX2 also suppressed the epidermal growth factor receptor/mitogen activated protein kinase (EGFR/MAPK) signaling pathway, leading to the decrease of the proliferation marker Ki-67 expression in nuclei. Furthermore, dual luciferase activity reduced capdependent protein translation in cells infected with sh-DX2. These results suggest that AIMP2-DX2 may be a relevant therapeutic target for lung cancer, and that the sh-DX2 lentiviral system can be an appropriate method for lung cancer therapy.

Genetic mapping and exome sequencing identify variants associated with five novel diseases

The Clinic for Special Children (CSC) has integrated biochemical and molecular methods into a rural pediatric practice serving Old Order Amish and Mennonite (Plain) children. Among the Plain people, we have used single nucleotide polymorphism (SNP) microarrays to genetically map recessive disorders to large autozygous haplotype blocks (mean = 4.4 Mb) that contain many genes (mean = 79). For some, uninformative mapping or large gene lists preclude disease-gene identification by Sanger sequencing. Seven such conditions were selected for exome sequencing at the Broad Institute; all had been previously mapped at the CSC using low density SNP microarrays coupled with autozygosity and linkage analyses. Using between 1 and 5 patient samples per disorder, we identified sequence variants in the known disease-causing genes SLC6A3 and FLVCR1, and present evidence to strongly support the pathogenicity of variants identified in TUBGCP6, BRAT1, SNIP1, CRADD, and HARS. Our results reveal the power of coupling new genotyping technologies to population-specific genetic knowledge and robust clinical data.

Expression and regulation of FAAP in the mouse epididymis

The focal adhesion-associated protein (FAAP), encoded by the murine D10Wsu52e gene, is named as involved in modulating cell adhesion dynamics. It is a highly conserved and ubiquitously expressed protein, and its human homologue HSPC117 has been identified in many protein complexes. However, the expression and regulation of the FAAP gene have not yet been well characterized. Herein, we demonstrate that FAAP mRNA and protein expression are highly regionalized in the mouse epididymis with predominant enrichment in the initial segment. During sexual maturation, FAAP mRNA is always expressed in the caput epididymides. Castration causes rapid and significant decrease of FAAP mRNA abundance within the initial segment, whereas testosterone replacement fails to reverse the regression. Unilateral orchidectomy and efferent duct ligation studies further validate that expression of the FAAP mRNA is highly dependent on the presence of luminal testicular factors rather than testosterone. Furthermore, FAAP expression in the initial segment is not affected by cryptorchism.

Flexibility and rigidity in protein crystals

There is an increasing body of crystallographic evidence for disorder in parts of the main polypeptide chain of certain proteins. The zymogens of pancreatic serine proteinases and tyrosyl-tRNA synthetase are used as examples. It is suggested that reactivity and specificity are favoured by an appropriate rigid conformation, and that disorder may often be involved in some kind of control function.

Identity elements of archaeal tRNA

Features unique to a transfer-RNA are recognized by the corresponding tRNA-synthetase. Keeping this in view we isolate the discriminating features of all archaeal tRNA. These are our identity elements. Further, we investigate tRNA-characteristics that delineate the different orders of Archaea.

Improved amber and opal suppressor tRNAs for incorporation of unnatural amino acids in vivo. Part 1: minimizing misacylation

The incorporation of unnatural amino acids site-specifically is a valuable technique for structure-function studies, incorporation of biophysical probes, and determining protein-protein interactions. THG73 is an amber suppressor tRNA used extensively for the incorporation of >100 different residues in over 20 proteins, but under certain conditions THG73 is aminoacylated in vivo by endogenous aminoacyl-tRNA synthetase. Similar aminoacylation is seen with the Escherichia coli Asn amber suppressor tRNA, which has also been used to incorporate UAAs in many studies. We now find that the natural amino acid placed on THG73 is Gln. Since the E. coli GlnRS recognizes positions in the acceptor stem, we made several acceptor stem mutations in the second to fourth positions on THG73. All mutations reduce aminoacylation in vivo and allow for the selection of highly orthogonal tRNAs. To show the generality of these mutations, we created opal suppressor tRNAs that show less aminoacylation in Xenopus oocytes relative to THG73. We have created a library of Tetrahymena thermophila Gln amber suppressor tRNAs that will be useful for determining optimal suppressor tRNAs for use in other eukaryotic cells.

The Saccharomyces cerevisiae Pus2 protein encoded by YGL063w ORF is a mitochondrial tRNA:Psi27/28-synthase

The RNA:pseudouridine (Psi)-synthase family is one of the most complex families of RNA modification enzymes. Ten genes encoding putative RNA:Psi-synthases have been identified in S. cerevisiae. Most of the encoded enzymes have been characterized experimentally. Only the putative RNA:Psi-synthase Pus2p (encoded by the YGL063w ORF) had no identified substrate. Here, we analyzed Psi residues in cytoplasmic and mitochondrial tRNAs extracted from S. cerevisiae strains, carrying disruptions in the PUS1 and/or PUS2 ORFs. Our results demonstrate that Pus2p is a mitochondrial-specific tRNA:Psi-synthase acting at positions 27 and 28 in tRNAs. The importance of the Asp56 residue in the conserved ARTD motif of the Pus2p catalytic site is demonstrated in vivo. Interestingly, in spite of the absence of a characteristic N-terminal targeting signal, our data strongly suggest an efficient and rapid targeting of Pus2p in yeast mitochondria. In contradiction with the commonly held idea that a unique nuclear gene encodes the enzyme required for both cytoplasmic and mitochondrial tRNA modifications, here we show the existence of an enzyme specifically dedicated to mitochondrial tRNA modification (Pus2p), the corresponding modification in cytoplasmic tRNAs being catalyzed by another protein (Pus1p).

Activation of the hetero-octameric ATP phosphoribosyl transferase through subunit interface rearrangement by a tRNA synthetase paralog

ATP phosphoribosyl transferase (ATP-PRT) joins ATP and 5-phosphoribosyl-1-pyrophosphate (PRPP) in a highly regulated reaction that initiates histidine biosynthesis. The unusual hetero-octameric version of ATP-PRT includes four HisG(S) catalytic subunits based on the periplasmic binding protein fold and four HisZ regulatory subunits that resemble histidyl-tRNA synthetases. Here, we present the first structure of a PRPP-bound ATP-PRT at 2.9 A and provide a structural model for allosteric activation based on comparisons with other inhibited and activated ATP-PRTs from both the hetero-octameric and hexameric families. The activated state of the octameric enzyme is characterized by an interstitial phosphate ion in the HisZ-HisG interface and new contacts between the HisZ motif 2 loop and the HisG(S) dimer interface. These contacts restructure the interface to recruit conserved residues to the active site, where they activate pyrophosphate to promote catalysis. Additionally, mutational analysis identifies the histidine binding sites within a region highly conserved between HisZ and the functional HisRS. Through the oligomerization and functional re-assignment of protein domains associated with aminoacylation and phosphate binding, the HisZ-HisG octameric ATP-PRT acquired the ability to initiate the synthesis of a key metabolic intermediate in an allosterically regulated fashion.

Recent progress of structural biology of tRNA processing and modification

Transfer RNA (tRNA) is a key molecule to decode the genetic information on mRNA to amino aicds (protein), in a ribosome. For tRNA to fulfill its adopter function, tRNA should be processed into the standard length, and be post-transcriptionally modified. This modification step is essential for the tRNA to maintain the canonical L-shaped structure, which is required for the decoding function of tRNA. Otherwise, it has recently been proposed that modification procedure itself contributes to the RNA (re)folding, where the modification enzymes function as a kind of RNA chaperones. Recent genome analyses and post-genome (proteomics and transcriptomics) analyses have identified genes involved in the tRNA processings and modifications. Furthermore, post-genomic structural analysis has elucidated the structural basis for the tRNA maturation mechanism. In this paper, the recent progress of the structural biology of the tRNA processing and modification is reviewed.