Integrated signaling and transcriptome analysis reveals Src family kinase individualities and novel pathways controlled by their constitutive activity

The Src family kinases (SFKs) Lck and Lyn are crucial for lymphocyte development and function. Albeit tissue-restricted expression patterns the two kinases share common functions; the most pronounced one being the phosphorylation of ITAM motifs in the cytoplasmic tails of antigenic receptors. Lck is predominantly expressed in T lymphocytes; however, it can be ectopically found in B-1 cell subsets and numerous pathologies including acute and chronic B-cell leukemias. The exact impact of Lck on the B-cell signaling apparatus remains enigmatic and is followed by the long-lasting question of mechanisms granting selectivity among SFK members. In this work we sought to investigate the mechanistic basis of ectopic Lck function in B-cells and compare it to events elicited by the predominant B-cell SFK, Lyn. Our results reveal substrate promiscuity displayed by the two SFKs, which however, is buffered by their differential susceptibility toward regulatory mechanisms, revealing a so far unappreciated aspect of SFK member-specific fine-tuning. Furthermore, we show that Lck- and Lyn-generated signals suffice to induce transcriptome alterations, reminiscent of B-cell activation, in the absence of receptor/co-receptor engagement. Finally, our analyses revealed a yet unrecognized role of SFKs in tipping the balance of cellular stress responses, by promoting the onset of ER-phagy, an as yet completely uncharacterized process in B lymphocytes

Studies on the structure and function of the protein subunits of the ribonucleoprotein RNase P from Dictyostelium discoideum

Ribonuclease P (RNase P) is a ubiquitous enzyme, which endonucleolytically cleaves the precursor tRNA transcripts to produce their mature 5' ends. Recently, RNase P has been found to participate in the transcription of tRNA, rRNA and other small non-coding RNA genes. RNase P occurs in representatives of all domains of life (bacteria, archaea, eukarya), as well as in mitochondria and chloroplasts, apart from the archeon Nanoarchaeum equitans. In almost every organism, RNase P is a ribonucleoprotein complex, with one essential RNA and a multiple number of protein subunits. There are only two exceptional cases, that of the human mitochondria and the plastids from A. thaliana, whose RNase P lacks an RNA subunit. The RNA subunit is responsible for the main catalytic function of the RNase P holoenzyme in bacteria, archaea and eukarya. Protein subunits are essential for catalysis in vivo and they play multiple roles in structure and function of the holoenzyme. Dictyostelium discoideum nuclear RNase P is the most proteinaceous holoenzyme among the eukaryal RNase P studied so far. It’s a ribonucleoprotein complex, which consists of one RNA and eight protein subunits (DRpp40, DRpp30, DRpp29, DRpp25, DRpp21, DRpp20, DPop1, DPop5). These proteins display similarities with its counterparts from higher eukaryotes, such as the human enzyme, but at the same time they retain distinctive characteristics. In the present study, we report the molecular cloning and interaction details of DRpp29 and RNase P RNA. Electromobility shift assays exhibited that DRpp29 binds specifically to the RNase P RNA subunit, a feature that was further confirmed by the molecular modeling of the DRpp29 structure. Moreover, deletion mutants of DRpp29 were constructed in order to investigate the domains of DRpp29 that contribute to and/or are responsible for the direct interaction with the D. discoideum RNase P RNA. A eukaryotic specific, lysine and arginine rich region was revealed, which seems to facilitate the interaction between these two subunits. We determined the D. discoideum RNase P RNA secondary structure based on footprinting analysis and bioinformatic data. Furthermore, footprinting analysis revealed that DRpp29 interact with the specificity domain (“S-domain”) of the RNA subunit, suggesting that DRpp29 influence the enzyme’s substrate binding ability. Furthermore, we tested the ability of wild type and mutant DRpp29 to form active RNase P enzymatic particles with the E. coli's RNase P RNA. Finally, we tested the formation of a minimal catalytic core of the D. discoideum RNase P, by performing homologous reconstitution experiments with DRpp29, its protein partner DRpp21 and the RNA subunit.Η ριβονουκλεάση P (RNase Ρ) είναι ένα πανταχού παρόν ένζυμο, το οποίο θραύει ενδονουκλεολυτικά τα πρόδρομα μετάγραφα των tRNA, παράγοντας τα ώριμα 5' άκρα τους. Πρόσφατα, βρέθηκε πως η RNase Ρ συμμετέχει στην μεταγραφή γονιδίων που κωδικοποιούν tRNA, rRNA και άλλα μικρά μη κωδικοποιούντα RNA. Η RNase Ρ έχει ανιχνευθεί σε αντιπροσώπους και των τριών περιοχών της ζωής (βακτήρια, αρχαία, ευκαρυώτες), καθώς επίσης σε μιτοχόνδρια και χλωροπλάστες, με μοναδική εξαίρεση το αρχαίο Nanoarchaeum equitans. Σε σχεδόν όλους τους οργανισμούς, η RNase Ρ είναι ένα ριβονουκλεοπρωτεϊνικό σύμπλοκο αποτελούμενο από μία απαραίτητη RNA υπομονάδα και ποικίλο αριθμό πρωτεϊνών. Υπάρχουν μόνο δύο, πρόσφατα, αναφερόμενες εξαιρέσεις, αυτές των ανθρώπινων μιτοχονδρίων και των πλαστιδίων του φυτού A. thaliana, των οποίων η RNase Ρ είναι αποκλειστικά πρωτεϊνικής φύσεως. Η RNA υπομονάδα είναι υπεύθυνη για την καταλυτική λειτουργία του ολοενζύμου της RNase Ρ από τα βακτήρια, τα αρχαία και τους ευκαρυώτες. Οι πρωτεϊνικές υπομονάδες είναι απαραίτητες για την κατάλυση in vivo και παίζουν πολλούς ρόλους στη δομή και λειτουργία του ολοενζύμου. Η πυρηνική RNase Ρ από το Dictyostelium discoideum είναι το πιο πλούσιο, σε πρωτεϊνική σύσταση, ολοένζυμο ανάμεσα στα ευκαρυωτικά ένζυμα RNase Ρ που έχουν μελετηθεί μέχρι σήμερα. Είναι ένα ριβονουκλεοπρωτεϊνικό σύμπλοκο, το οποίο αποτελείται από μια RNA υπομονάδα και οχτώ πρωτεΐνες (DRpp40, DRpp30, DRpp29, DRpp25, DRpp21, DRpp20, DPop1, DPop5). Αυτές οι πρωτεΐνες παρουσιάζουν ομοιότητες με τις ομόλογές τους από ανώτερα ευκαρυωτικά ένζυμα, όπως του ανθρώπου, ενώ παράλληλα διατηρούν ιδιοσυγκρασιακά χαρακτηριστικά. Στην παρούσα μελέτη, περιγράφουμε την κλωνοποίηση και τις ιδιότητες αλληλεπίδρασης της πρωτεΐνης DRpp29 με την RNA υπομονάδα της RNase Ρ του D. discoideum. Πειράματα ηλεκτροφορητικής κινητικότητας έδειξαν, πως η DRpp29 δεσμεύεται ειδικά με την RNA υπομονάδα, ένα χαρακτηριστικό που επιβεβαιώθηκε περαιτέρω με τον σχεδιασμό του μοντέλου της δομής της DRpp29. Επιπλέον, κατασκευάστηκαν μεταλλάγματα απολοιφής της DRpp29, για να μελετηθούν οι περιοχές της DRpp29 που συνεισφέρουν ή/και είναι υπεύθυνες για την άμεση αλληλεπίδρασή της με την RNA υπομονάδα. Εντοπίστηκε μια περιοχή, μεταξύ των ευκαρυωτικών ομολόγων, πλούσια σε λυσίνες και αργινίνες, η οποία φαίνεται να διευκολύνει την αλληλεπίδραση των δύο αυτών υπομονάδων. Προσδιορίσαμε, επίσης, με τη διεξαγωγή ανάλυσης αποτυπώματος και τη χρήση δεδομένων βιοπληροφορικής, τη δευτεροταγή δομή της RNA υπομονάδας της RNase Ρ του D. discoideum. Με ανάλυση αποτυπώματος αποκαλύφθηκε, πως η DRpp29 αλληλεπιδρά με την περιοχή εξειδίκευσης (“S-domain”) της RNA υπομονάδας, δείχνοντας, ότι η DRpp29 επηρεάζει την ικανότητα δέσμευσης του υποστρώματος από το ένζυμο. Στη συνέχεια, ελέγχθη η ικανότητα της DRpp29 και των μεταλλαγμάτων της να σχηματίζουν, μαζί με την RNA υπομονάδα του Ε. coli, ενεργά ενζυμικά σύμπλοκα με δραστικότητα RNase Ρ. Τέλος, ελέγχθη ο σχηματισμός ενός ελάχιστα καταλυτικού πυρήνα της RNase Ρ του D. discoideum, με την πραγματοποίηση πειραμάτων ομόλογης ανασύστασης με την DRpp29, τον πρωτεϊνικό της συνεργάτη DRpp21 και την RNA υπομονάδα

Low-budget collection management at the Criminal Museum, School of Forensic Medicine, University of Athens

In Greece, the Criminal Museum is unique in its kind. Founded by the School of Forensic Medicine of the University of Athens in 1933. it has a collection of materials connected to infamous crimes and violations that took place in Greece during the twentieth century. For several years, the Museum faced serious problems in relation to both the collection and exhibition. In 1999, the School of Forensic Medicine established a collaborative project together with the Department of Conservation of Antiquities and Works of Art of the Technical and Educational Institute in Athens in order to improve the museum's facilities. This paper explains the measures taken to improve the facilities for display and for preserving the collection on a low budget and employing both preventive and interventionist approaches.O Museu Criminal é o ùnico do seu tipo na Grècia. Foi fundado pela Escola de Medicina Forense da Universidade de Atenas em 1933 e possui urna colecçâo de peças do século XX relacionadas com crimes infâmes e violaçôes. Durante largos anos, o Museu enfrentou sérios problemas relacionados com o estado de conservaçâo das colecçôes e desajustamento da exposiçâo. Em 1999, a Escola de Medicina Forense estabeleceu um protocolo de colaboraçâo com o Departamento de Conservaçâo de Antiguidades e Obras de Arte do Institute Tècnico e de Educaçâo de Atenas por forma a memorar a qualidade gérai das instalaçôes. Este artigo descreve as principais medidas de conservaçâo e de intervençâo tomadas durante o processo

A Riboswitch-Driven Era of New Antibacterials

Riboswitches are structured non-coding RNAs found in the 5′ UTR of important genes for bacterial metabolism, virulence and survival. Upon the binding of specific ligands that can vary from simple ions to complex molecules such as nucleotides and tRNAs, riboswitches change their local and global mRNA conformations to affect downstream transcription or translation. Due to their dynamic nature and central regulatory role in bacterial metabolism, riboswitches have been exploited as novel RNA-based targets for the development of new generation antibacterials that can overcome drug-resistance problems. During recent years, several important riboswitch structures from many bacterial representatives, including several prominent human pathogens, have shown that riboswitches are ideal RNA targets for new compounds that can interfere with their structure and function, exhibiting much reduced resistance over time. Most interestingly, mainstream antibiotics that target the ribosome have been shown to effectively modulate the regulatory behavior and capacity of several riboswitches, both in vivo and in vitro, emphasizing the need for more in-depth studies and biological evaluation of new antibiotics. Herein, we summarize the currently known compounds that target several main riboswitches and discuss the role of mainstream antibiotics as modulators of T-box riboswitches, in the dawn of an era of novel inhibitors that target important bacterial regulatory RNAs

Probing the human nucleolar proteome for novel pre-rRNA processing factors.

info:eu-repo/semantics/nonPublishe

Use of the iNo score to discriminate normal from altered nucleolar morphology, with applications in basic cell biology and potential in human disease diagnostics

Ribosome biogenesis is initiated in the nucleolus, a cell condensate essential to gene expression, whose morphology informs cancer pathologists on the health status of a cell. Here, we describe a protocol for assessing, both qualitatively and quantitatively, the involvement of trans-acting factors in the nucleolar structure. The protocol involves use of siRNAs to deplete cells of factors of interest, fluorescence imaging of nucleoli in an automated high-throughput platform, and use of dedicated software to determine an index of nucleolar disruption, the iNo score. This scoring system is unique in that it integrates the five most discriminant shape and textural features of the nucleolus into a parametric equation. Determining the iNo score enables both qualitative and quantitative factor classification with prediction of function (functional clustering), which to our knowledge is not achieved by competing approaches, as well as stratification of their effect (severity of defects) on nucleolar structure. The iNo score has the potential to be useful in basic cell biology (nucleolar structure–function relationships, mitosis, and senescence), developmental and/or organismal biology (aging), and clinical practice (cancer, viral infection, and reproduction). The entire protocol can be completed within 1 week

Structural basis of amino acid surveillance by higher-order tRNA-mRNA interactions

Amino acid availability in Gram-positive bacteria is monitored by T-box riboswitches. T-boxes directly bind tRNAs, assess their aminoacylation state, and regulate the transcription or translation of downstream genes to maintain nutritional homeostasis. Here, we report cocrystal and cryo-EM structures of Geobacillus kaustophilus and Bacillus subtilis T-box-tRNA complexes, detailing their multivalent, exquisitely selective interactions. The T-box forms a U-shaped molecular vise that clamps the tRNA, captures its 3' end using an elaborate 'discriminator' structure, and interrogates its aminoacylation state using a steric filter fashioned from a wobble base pair. In the absence of aminoacylation, T-boxes clutch tRNAs and form a continuously stacked central spine, permitting transcriptional readthrough or translation initiation. A modeled aminoacyl disrupts tRNA-T-box stacking, severing the central spine and blocking gene expression. Our data establish a universal mechanism of amino acid sensing on tRNAs and gene regulation by T-box riboswitches and exemplify how higher-order RNA-RNA interactions achieve multivalency and specificity