A novel 3' splice site recognition by the two zinc fingers in the U2AF small subunit.

The pre-mRNA splicing reaction of eukaryotic cells has to be carried out extremely accurately, as failure to recognize the splice sites correctly causes serious disease. The small subunit of the U2AF heterodimer is essential for the determination of 3' splice sites in pre-mRNA splicing, and several single-residue mutations of the U2AF small subunit cause severe disorders such as myelodysplastic syndromes. However, the mechanism of RNA recognition is poorly understood. Here we solved the crystal structure of the U2AF small subunit (U2AF23) from fission yeast, consisting of an RNA recognition motif (RRM) domain flanked by two conserved CCCH-type zinc fingers (ZFs). The two ZFs are positioned side by side on the ß sheet of the RRM domain. Further mutational analysis revealed that the ZFs bind cooperatively to the target RNA sequence, but the RRM domain acts simply as a scaffold to organize the ZFs and does not itself contact the RNA directly. This completely novel and unexpected mode of RNA-binding mechanism by the U2AF small subunit sheds light on splicing errors caused by mutations of this highly conserved protein.

Medical costs of Japanese lung cancer patients during end-of-life care.

OBJECTIVE: The medical costs associated with cancer treatment have increased rapidly in Japan; however, little data exist on actual costs, especially for end-of-life care. Therefore, this study aimed to examine the medical costs of lung cancer patients during the last 3 months before death and to compare the costs with those of initial anticancer treatment. METHODS: We retrospectively evaluated all patients who died from lung cancer at the Japanese Red Cross Medical Center between 1 January 2008 and 31 August 2019. Patients were classified into three cohorts (2008-2011, 2012-2015 and 2016-2019) according to the year of death; the medical costs were evaluated for each cohort. Costs were then divided into outpatient and inpatient costs and calculated per month. RESULTS: Seventy-nine small cell lung cancer and 213 non-small cell lung cancer patients were included. For small cell lung cancer and non-small cell lung cancer patients, most end-of-life medical costs were inpatient costs across all cohorts. The median monthly medical costs for the last 3 months among both small cell lung cancer and non-small cell lung cancer patients did not differ significantly among the cohorts, but the mean monthly costs for non-small cell lung cancer tended to increase. The monthly medical costs for the last 3 months were significantly higher than those for the first year in SCLC (P = 0.013) and non-small cell lung cancer (P < 0.001) patients and those for the first 3 months in non-small cell lung cancer patients (P = 0.005). CONCLUSIONS: The medical costs during the end-of-life period for lung cancer were high and surpassed those for initial treatment.

Medical costs of lung cancer care in Japan during the first one or two years after initial diagnosis.

OBJECTIVES: Japan's healthcare expenditures, especially on oncology, are rapidly growing; however, there are scant data on actual costs and cost-effectiveness in the real world. The aim was to assess the medical costs and outcomes of patients with advanced lung cancer. METHODS: We retrospectively investigated all patients who were diagnosed with advanced lung cancer at the Japanese Red Cross Medical Center between 1 January 2008 and 31 December 2018. Patients were classified into three cohorts according to the year of diagnosis-Cohort 1: 2008-2010, Cohort 2: 2011-2014 and Cohort 3: 2015-2018-and assessed for medical costs and outcome. Medical costs were divided into outpatient and inpatient costs and were calculated on a monthly basis. RESULTS: Ninety-five patients with small cell lung cancer (SCLC) and 330 with nonsmall cell lung cancer (NSCLC) were included. There was a trend toward increased costs during the first two years after diagnosis in NSCLC patients, without changes in monthly costs, reflecting improved survival. Compared to Cohort 1, Cohort 3 patients with NSCLC had longer survival (median: 24 versus 12 months, P < 0.001), with a median incremental cost of Japanese Yen 6 million during the initial two years. The proportion of outpatient costs increased over time, especially for NSCLC patients (P < 0.001). No changes in costs or survival were observed in SCLC patients. CONCLUSIONS: In NSCLC patients, medical costs increased with prolonged survival during the last decade. The costs on a monthly basis did not change. The proportion of outpatient costs increased.

Drug-induced hypersensitivity syndrome caused by minodronic acid hydrate.

BACKGROUND: Drug-induced hypersensitivity syndrome (DIHS)/drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is an important adverse reaction caused by a few drugs. Reactivation of human herpesvirus 6 (HHV-6) is known to be associated with its pathogenesis. DIHS occasionally manifests as pulmonary lesions with a variety of imaging findings. CASE PRESENTATION: An 83-year-old woman started taking minodronic acid hydrate 5 years before admission. She noticed a generalized skin rash 44 days before admission and started oral betamethasone-d-chlorpheniramine maleate combination tablets for allergic dermatitis. She developed a fever and cough in addition to the rash, and was referred to our hospital. Laboratory data showed a high level of eosinophils and liver and biliary enzymes. Computed tomography (CT) studies revealed bilateral diffuse ground-glass opacities with ill-defined centrilobular nodules from the central to peripheral regions of the lungs. Transbronchial lung cryobiopsy specimens showed that lymphocyte infiltration was observed in the alveolar walls and fibrinous exudates and floating macrophages in the alveolar lumina. Immunohistochemistry of biopsy specimens showed more CD4+ lymphocytes than CD8+ lymphocytes, while few Foxp3+ lymphocytes were recognized. The serum anti-HHV-6 immunoglobulin G titer increased at 3 weeks after the first test. Based on these findings, we diagnosed her with DIHS. We continued care without using corticosteroids since there was no worsening of breathing or skin condition. Eventually, her clinical symptoms chest CT had improved. Minodronic acid hydrate was identified as the culprit drug based on the positive results of the patch test and drug-induced lymphocyte stimulation test. CONCLUSIONS: We described the first case of DIHS caused by minodronic acid hydrate. Lung lesions in DIHS can present with bilateral diffuse ground-glass opacities and ill-defined centrilobular nodules on a CT scan during the recovery phase. Clinicians should be aware of DIHS, even if patients are not involved with typical DIHS/DRESS-causing drugs.

Glycolytic flux controls D-serine synthesis through glyceraldehyde-3-phosphate dehydrogenase in astrocytes.

D-Serine is an essential coagonist with glutamate for stimulation of N-methyl-D-aspartate (NMDA) glutamate receptors. Although astrocytic metabolic processes are known to regulate synaptic glutamate levels, mechanisms that control D-serine levels are not well defined. Here we show that d-serine production in astrocytes is modulated by the interaction between the D-serine synthetic enzyme serine racemase (SRR) and a glycolytic enzyme, glyceraldehyde 3-phosphate dehydrogenase (GAPDH). In primary cultured astrocytes, glycolysis activity was negatively correlated with D-serine level. We show that SRR interacts directly with GAPDH, and that activation of glycolysis augments this interaction. Biochemical assays using mutant forms of GAPDH with either reduced activity or reduced affinity to SRR revealed that GAPDH suppresses SRR activity by direct binding to GAPDH and through NADH, a product of GAPDH. NADH allosterically inhibits the activity of SRR by promoting the disassociation of ATP from SRR. Thus, astrocytic production of D-serine is modulated by glycolytic activity via interactions between GAPDH and SRR. We found that SRR is expressed in astrocytes in the subiculum of the human hippocampus, where neurons are known to be particularly vulnerable to loss of energy. Collectively, our findings suggest that astrocytic energy metabolism controls D-serine production, thereby influencing glutamatergic neurotransmission in the hippocampus.

Structure, Dynamics, and Interaction of p54(nrb)/NonO RRM1 with 5' Splice Site RNA Sequence.

p54(nrb)/NonO is a nuclear RNA-binding protein involved in many cellular events such as pre-mRNA processing, transcription, and nuclear retention of hyper-edited RNAs. In particular, it participates in the splicing process by directly binding the 5' splice site of pre-mRNAs. The protein also concentrates in a nuclear body called paraspeckle by binding a G-rich segment of the ncRNA NEAT1. The N-terminal section of p54(nrb)/NonO contains tandem RNA recognition motifs (RRMs) preceded by an HQ-rich region including a threonine residue (Thr15) whose phosphorylation inhibits its RNA binding ability, except for G-rich RNAs. In this work, our goal was to understand the rules that characterize the binding of the p54(nrb)/NonO RRMs to their RNA target. We have done in vitro RNA binding experiments which revealed that only the first RRM of p54(nrb)/NonO binds to the 5' splice site RNA. We have then determined the structure of the p54(nrb)/NonO RRM1 by liquid-state NMR which revealed the presence of a canonical fold (ß1α1ß2ß3α2ß4) and the conservation of aromatic amino acids at the protein surface. We also investigated the dynamics of this domain by NMR. The p54(nrb)/NonO RRM1 displays some motional properties that are typical of a well-folded protein with some regions exhibiting more flexibility (loops and ß-strands). Furthermore, we determined the affinity of p54(nrb)/NonO RRM1 interaction to the 5' splice site RNA by NMR and fluorescence quenching and mapped its binding interface by NMR, concluding in a classical nucleic acid interaction. This study provides an improved understanding of the molecular basis (structure and dynamics) that governs the binding of the p54(nrb)/NonO RRM1 to one of its target RNAs.

Controlling the fluorescence of benzofuran-modified uracil residues in oligonucleotides by triple-helix formation.

We developed fluorescent turn-on probes containing a fluorescent nucleoside, 5-(benzofuran-2-yl)deoxyuridine (dU(BF)) or 5-(3-methylbenzofuran-2-yl)deoxyuridine (dU(MBF)), for the detection of single-stranded DNA or RNA by utilizing DNA triplex formation. Fluorescence measurements revealed that the probe containing dU(MBF) achieved superior fluorescence enhancement than that containing dU(BF). NMR and fluorescence analyses indicated that the fluorescence intensity increased upon triplex formation partly as a consequence of a conformational change at the bond between the 3-methylbenzofuran and uracil rings. In addition, it is suggested that the microenvironment around the 3-methylbenzofuran ring contributed to the fluorescence enhancement. Further, we developed a method for detecting RNA by rolling circular amplification in combination with triplex-induced fluorescence enhancement of the oligonucleotide probe containing dU(MBF).

Aberrant assembly of RNA recognition motif 1 links to pathogenic conversion of TAR DNA-binding protein of 43 kDa (TDP-43).

Aggregation of TAR DNA-binding protein of 43 kDa (TDP-43) is a pathological signature of amyotrophic lateral sclerosis (ALS). Although accumulating evidence suggests the involvement of RNA recognition motifs (RRMs) in TDP-43 proteinopathy, it remains unclear how native TDP-43 is converted to pathogenic forms. To elucidate the role of homeostasis of RRM1 structure in ALS pathogenesis, conformations of RRM1 under high pressure were monitored by NMR. We first found that RRM1 was prone to aggregation and had three regions showing stable chemical shifts during misfolding. Moreover, mass spectrometric analysis of aggregated RRM1 revealed that one of the regions was located on protease-resistant ß-strands containing two cysteines (Cys-173 and Cys-175), indicating that this region served as a core assembly interface in RRM1 aggregation. Although a fraction of RRM1 aggregates comprised disulfide-bonded oligomers, the substitution of cysteine(s) to serine(s) (C/S) resulted in unexpected acceleration of amyloid fibrils of RRM1 and disulfide-independent aggregate formation of full-length TDP-43. Notably, TDP-43 aggregates with RRM1-C/S required the C terminus, and replicated cytopathologies of ALS, including mislocalization, impaired RNA splicing, ubiquitination, phosphorylation, and motor neuron toxicity. Furthermore, RRM1-C/S accentuated inclusions of familial ALS-linked TDP-43 mutants in the C terminus. The relevance of RRM1-C/S-induced TDP-43 aggregates in ALS pathogenesis was verified by immunolabeling of inclusions of ALS patients and cultured cells overexpressing the RRM1-C/S TDP-43 with antibody targeting misfolding-relevant regions. Our results indicate that cysteines in RRM1 crucially govern the conformation of TDP-43, and aberrant self-assembly of RRM1 at amyloidogenic regions contributes to pathogenic conversion of TDP-43 in ALS.

Dual-site interactions of p53 protein transactivation domain with anti-apoptotic Bcl-2 family proteins reveal a highly convergent mechanism of divergent p53 pathways.

Molecular interactions between the tumor suppressor p53 and the anti-apoptotic Bcl-2 family proteins play an important role in the transcription-independent apoptosis of p53. The p53 transactivation domain (p53TAD) contains two conserved ΦXXΦΦ motifs (Φ indicates a bulky hydrophobic residue and X is any other residue) referred to as p53TAD1 (residues 15-29) and p53TAD2 (residues 39-57). We previously showed that p53TAD1 can act as a binding motif for anti-apoptotic Bcl-2 family proteins. In this study, we have identified p53TAD2 as a binding motif for anti-apoptotic Bcl-2 family proteins by using NMR spectroscopy, and we calculated the structures of Bcl-X(L)/Bcl-2 in complex with the p53TAD2 peptide. NMR chemical shift perturbation data showed that p53TAD2 peptide binds to diverse members of the anti-apoptotic Bcl-2 family independently of p53TAD1, and the binding between p53TAD2 and p53TAD1 to Bcl-X(L) is competitive. Refined structural models of the Bcl-X(L)·p53TAD2 and Bcl-2·p53TAD2 complexes showed that the binding sites occupied by p53TAD2 in Bcl-X(L) and Bcl-2 overlap well with those occupied by pro-apoptotic BH3 peptides. Taken together with the mutagenesis, isothermal titration calorimetry, and paramagnetic relaxation enhancement data, our structural comparisons provided the structural basis of p53TAD2-mediated interaction with the anti-apoptotic proteins, revealing that Bcl-X(L)/Bcl-2, MDM2, and cAMP-response element-binding protein-binding protein/p300 share highly similar modes of binding to the dual p53TAD motifs, p53TAD1 and p53TAD2. In conclusion, our results suggest that the dual-site interaction of p53TAD is a highly conserved mechanism underlying target protein binding in the transcription-dependent and transcription-independent apoptotic pathways of p53.

Novel RNA recognition motif domain in the cytoplasmic polyadenylation element binding protein 3.

The family of cytoplasmic polyadenylation element binding proteins CPEB1, CPEB2, CPEB3, and CPEB4 binds to the 3'-untranslated region (3'-UTR) of mRNA, and plays significant roles in mRNA metabolism and translation regulation. They have a common domain organization, involving two consecutive RNA recognition motif (RRM) domains followed by a zinc finger domain in the C-terminal region. We solved the solution structure of the first RRM domain (RRM1) of human CPEB3, which revealed that CPEB3 RRM1 exhibits structural features distinct from those of the canonical RRM domain. Our structural data provide important information about the RNA binding ability of CPEB3 RRM1.

1H, 13C, and 15N resonance assignments and solution structure of the N-terminal divergent calponin homology (NN-CH) domain of human intraflagellar transport protein 54.

The intraflagellar transport (IFT) machinery plays a crucial role in the bidirectional trafficking of components necessary for ciliary signaling, such as the Hedgehog, Wnt/PCR, and cAMP/PKA systems. Defects in some components of the IFT machinery cause dysfunction, leading to a wide range of human diseases and developmental disorders termed ciliopathies, such as nephronophthisis. The IFT machinery comprises three sub-complexes: BBsome, IFT-A, and IFT-B. The IFT protein 54 (IFT54) is an important component of the IFT-B sub-complex. In anterograde movement, IFT54 binds to active kinesin-II, walking along the cilia microtubule axoneme and carrying the dynein-2 complex in an inactive state, which works for retrograde movement. Several mutations in IFT54 are known to cause Senior-Loken syndrome, a ciliopathy. IFT54 possesses a divergent Calponin Homology (CH) domain termed as NN-CH domain at its N-terminus. However, several aspects of the function of the NN-CH domain of IFT54 are still obscure. Here, we report the 1H, 15N, and 13C resonance assignments of the NN-CH domain of human IFT54 and its solution structure. The NN-CH domain of human IFT54 adopts essentially the α1-α2-α3-α4-α5 topology as that of mouse IFT54, whose structure was determined by X-ray crystallographic study. The structural information and assignments obtained in this study shed light on the molecular function of the NN-CH domain in IFT54.

Structural basis for the dual RNA-recognition modes of human Tra2-ß RRM.

Human Transformer2-ß (hTra2-ß) is an important member of the serine/arginine-rich protein family, and contains one RNA recognition motif (RRM). It controls the alternative splicing of several pre-mRNAs, including those of the calcitonin/calcitonin gene-related peptide (CGRP), the survival motor neuron 1 (SMN1) protein and the tau protein. Accordingly, the RRM of hTra2-ß specifically binds to two types of RNA sequences [the CAA and (GAA)(2) sequences]. We determined the solution structure of the hTra2-ß RRM (spanning residues Asn110-Thr201), which not only has a canonical RRM fold, but also an unusual alignment of the aromatic amino acids on the ß-sheet surface. We then solved the complex structure of the hTra2-ß RRM with the (GAA)(2) sequence, and found that the AGAA tetra-nucleotide was specifically recognized through hydrogen-bond formation with several amino acids on the N- and C-terminal extensions, as well as stacking interactions mediated by the unusually aligned aromatic rings on the ß-sheet surface. Further NMR experiments revealed that the hTra2-ß RRM recognizes the CAA sequence when it is integrated in the stem-loop structure. This study indicates that the hTra2-ß RRM recognizes two types of RNA sequences in different RNA binding modes.

Structural insights into recognition of SL4, the UUCG stem-loop, of human U1 snRNA by the ubiquitin-like domain, including the C-terminal tail in the SF3A1 subunit of U2 snRNP.

The pre-spliceosomal complex involves interactions between U1 and U2 snRNPs, where a ubiquitin-like domain (ULD) of SF3A1, a component of U2 snRNP, binds to the stem-loop 4 (SL4; the UUCG tetraloop) of U1 snRNA in U1 snRNP. Here, we reported the 1.80 Å crystal structure of human SF3A1 ULD (ULDSF3A1) complexed with SL4. The structural part of ULDSF3A1 (res. 704-785) adopts a typical ß-grasp fold with a topology of ß1-ß2-α1-310a-ß3-ß4-310b-ß5, closely resembling that of ubiquitin, except for the length and structure of the ß1/ß2 loop. A patch on the surface formed by three ULDSF3A1-specific residues, Lys756 (ß3), Phe763 (ß4) and Lys765 (following ß4), contacts the canonical UUCG tetraloop structure. In contrast, the directly following C-terminal tail composed of 786KERGGRKK793 was essentially stretched. The main or side chains of all the residues interacted with the major groove of the stem helix; the RGG residues adopted a peculiar conformation for RNA recognition. These findings were confirmed by mutational studies using bio-layer interferometry. Collectively, a unique combination of the ß-grasp fold and the C-terminal tail constituting ULDSF3A1 is required for the SL4-specific binding. This interaction mode also suggests that putative post-translational modifications, including ubiquitination in ULDSF3A1, directly inhibit SL4 binding.

Adult T-cell leukemia/lymphoma complicated by Pneumocystis pneumonia in a non-endemic area.

Adult T-cell leukemia/lymphoma (ATLL) is a human T-cell leukemia virus type 1-inducing unevenly-distributed T-cell malignancy, which is often complicated by opportunistic infections. Here, we discuss the case of a 75-year-old woman presenting with Pneumocystis pneumonia (PCP) who was subsequently diagnosed with ATLL in Tokyo, a non-endemic area of ATLL. In addition to the elevated soluble interleukin-2 receptor and the detection of flower cells in the screening blood test, the high-resolution computed tomography findings, atypical of PCP, were clues to the diagnosis of ATLL. ATLL should be considered as an underlying disease when patients present with PCP, even in non-endemic areas.

Solution structures of the double-stranded RNA-binding domains from RNA helicase A.

RNA helicase A (RHA) is a highly conserved protein with multifaceted functions in the gene expression of cellular and viral mRNAs. RHA recognizes highly structured nucleotides and catalytically rearranges the various interactions between RNA, DNA, and protein molecules to provide a platform for the ribonucleoprotein complex. We present the first solution structures of the double-stranded RNA-binding domains (dsRBDs), dsRBD1 and dsRBD2, from mouse RHA. We discuss the binding mode of the dsRBDs of RHA, in comparison with the known dsRBD structures in their complexes. Our structural data provide important information for the elucidation of the molecular reassembly mediated by RHA.

Structural insights into the dual-targeting mechanism of Nutlin-3.

Multi-targeting therapy is an emerging strategy of drug discovery to improve therapeutic efficacy, safety and resistance profiles. In this study, we monitored the binding of a potent MDM2 inhibitor Nutlin-3 with anti-apoptotic Bcl-2 family proteins using NMR spectroscopy. Our results showed the universal binding of Nutlin-3 with diverse anti-apoptotic Bcl-2 family proteins. Taken together with the binding data for Nutlin-3 analogs, the structural model of the Bcl-X(L)/Nutlin-3 complex showed that the binding mode of Nutlin-3 resembles that of the Bcl-X(L)/Bcl-2 inhibitors, suggesting the molecular mechanism of transcription-independent mitochondrial apoptosis by Nutlin-3. Finally, our structural comparison provides structural insights into the dual-targeting mechanism of how Nutlin-3 can bind to two different target proteins, MDM2 and anti-apoptotic Bcl-2 family proteins in a similar manner.

Therapeutic options in thymomas and thymic carcinomas.

INTRODUCTION: Curative-intent surgery is the best therapeutic option for thymic malignancies. However, patients with advanced or recurrent thymic malignancies often require palliative-intent chemotherapy or radiotherapy. Since thymic malignancies are rare cancers, the efficacy and safety of treatments have been verified based on small Phase 2 trials or retrospective studies. AREA COVERED: We comprehensively reviewed the treatment strategies for thymic malignancies, including surgery, radiotherapy, and pharmacotherapy, including cytotoxic chemotherapy, molecular-targeted therapy, and immunotherapy. Additionally, we reviewed specific situations, such as pleural dissemination, central nervous system metastasis, and paraneoplastic syndrome. EXPERT OPINION: Cytotoxic chemotherapy remains the standard option in pharmacotherapy. However, multikinase inhibitors, such as sunitinib and lenvatinib, and immune checkpoint inhibitors including pembrolizumab have been developed to treat thymic carcinomas. Now, a Phase 2 study is evaluating whether lenvatinib plus pembrolizumab benefits patients with type B3 thymoma or thymic carcinoma. Phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin inhibitors may contribute to disease control and octreotide scan is only applicable to somatostatin analogues. Although the genomic characteristics of thymic malignancies have been analyzed, few actionable mutations have been detected in general. The development of a treatment strategy using combination pharmacotherapy is anticipated.

Clinical Utility of Rapid On-Site Evaluation of Touch Imprint Cytology during Cryobiopsy for Peripheral Pulmonary Lesions.

Cryobiopsy enables us to obtain larger specimens than conventional forceps biopsy despite the caution regarding complications. This study aimed to evaluate the clinical utility of rapid on-site evaluation of touch imprint cytology (ROSE-TIC) during cryobiopsy of peripheral pulmonary lesions (PPLs). We retrospectively reviewed the data of consecutive patients who underwent cryobiopsy for solid PPLs between June 2020 and December 2021. ROSE-TIC was performed on the first specimen obtained via cryobiopsy and assessed using Diff-Quik staining. The results of ROSE-TIC for each patient were compared with the histological findings of the first cryobiopsy specimen. Sixty-three patients were enrolled in this study. Overall, 57 (90.5%) lesions were ≤30 mm in size and 37 (58.7%) had positive bronchus signs. The radial endobronchial ultrasound findings were located within and adjacent to the lesion in 46.0% and 54.0% of the cases, respectively. The sensitivity, specificity, and positive and negative predictive values of the ROSE results for histological findings of the corresponding specimens were 69.8%, 90.0%, 93.8%, and 58.1%, respectively. The concordance rate was 76.2%. In conclusion, ROSE-TIC, due to its high specificity and positive predictive value, may be a potential tool in deciding whether cryobiopsy sampling could be finished during bronchoscopy.

Structural basis for the interaction between the first SURP domain of the SF3A1 subunit in U2 snRNP and the human splicing factor SF1.

SURP domains are exclusively found in splicing-related proteins in all eukaryotes. SF3A1, a component of the U2 snRNP, has two tandem SURP domains, SURP1, and SURP2. SURP2 is permanently associated with a specific short region of SF3A3 within the SF3A protein complex whereas, SURP1 binds to the splicing factor SF1 for recruitment of U2 snRNP to the early spliceosomal complex, from which SF1 is dissociated during complex conversion. Here, we determined the solution structure of the complex of SURP1 and the human SF1 fragment using nuclear magnetic resonance (NMR) methods. SURP1 adopts the canonical topology of α1-α2-310 -α3, in which α1 and α2 are connected by a single glycine residue in a particular backbone conformation, allowing the two α-helices to be fixed at an acute angle. A hydrophobic patch, which is part of the characteristic surface formed by α1 and α2, specifically contacts a hydrophobic cluster on a 16-residue α-helix of the SF1 fragment. Furthermore, whereas only hydrophobic interactions occurred between SURP2 and the SF3A3 fragment, several salt bridges and hydrogen bonds were found between the residues of SURP1 and the SF1 fragment. This finding was confirmed through mutational studies using bio-layer interferometry. The study also revealed that the dissociation constant between SURP1 and the SF1 fragment peptide was approximately 20 µM, indicating a weak or transient interaction. Collectively, these results indicate that the interplay between U2 snRNP and SF1 involves a transient interaction of SURP1, and this transient interaction appears to be common to most SURP domains, except for SURP2.

An autopsy case of idiopathic pulmonary fibrosis with remarkable honeycomb cyst expansion.

Herein, we report an autopsy case of idiopathic pulmonary fibrosis (IPF) in which remarkable honeycomb cyst expansion appeared in the clinical course. Radiological findings initially showed subpleural predominant reticulation that had progressed to usual interstitial pneumonia with honeycomb cysts, along with a restrictive pattern in the pulmonary function tests. The diameter of honeycomb cysts had gradually increased, and some cysts had abruptly expanded at the end stage. Based on pathological findings of autopsy specimens, bronchiectasis, alveolar collapse due to inflammation, and check-valve mechanism caused by a slit-like orifice of the cysts could have contributed to honeycomb cyst expansion.