Direct activation of RNA polymerase III transcription by c-Myc

The proto-oncogene product c-Myc has a direct role in both metazoan cell growth and division. RNA polymerase III (pol III) is involved in the generation of transfer RNA and 5S ribosomal RNA, and these molecules must be produced in bulk to meet the need for protein synthesis in growing cells. We demonstrate here that c-Myc binds to TFIIIB, a pol III-specific general transcription factor, and directly activates pol III transcription. Chromatin immunoprecipitation reveals that endogenous c-Myc is present at tRNA and 5S rRNA genes in cultured mammalian cells. These results suggest that activation of pol III may have a role in the ability of c-Myc to stimulate cell growt

Depicting conformational ensembles of \u3b1-synuclein by single molecule force spectroscopy and native mass spectroscopy

Description of heterogeneous molecular ensembles, such as intrinsically disordered proteins, represents a challenge in structural biology and an urgent question posed by biochemistry to interpret many physiologically important, regulatory mechanisms. Single-molecule techniques can provide a unique contribution to this field. This work applies single molecule force spectroscopy to probe conformational properties of \u3b1-synuclein in solution and its conformational changes induced by ligand binding. The goal is to compare data from such an approach with those obtained by native mass spectrometry. These two orthogonal, biophysical methods are found to deliver a complex picture, in which monomeric \u3b1-synuclein in solution spontaneously populates compact and partially compacted states, which are differently stabilized by binding to aggregation inhibitors, such as dopamine and epigallocatechin-3-gallate. Analyses by circular dichroism and Fourier-transform infrared spectroscopy show that these transitions do not involve formation of secondary structure. This comparative analysis provides support to structural interpretation of charge-state distributions obtained by native mass spectrometry and helps, in turn, defining the conformational components detected by single molecule force spectroscopy

Werner syndrome protein limits MYC-induced cellular senescence - Supplementary Materials Only

The MYC oncoprotein is a transcription factor that coordinates cell growth and division. MYC overexpression exacerbates genomic instability and sensitizes cells to apoptotic stimuli. Here we demonstrate that MYC directly stimulates transcription of the human Werner syndrome gene, WRN, which encodes a conserved RecQ helicase. Loss-of-function mutations in WRN lead to genomic instability, an elevated cancer risk, and premature cellular senescence. The overexpression of MYC in WRN syndrome fibroblasts or after WRN depletion from control fibroblasts led to rapid cellular senescence that could not be suppressed by hTERT expression. We propose that WRN up-regulation by MYC may promote MYC-driven tumorigenesis by preventing cellular senescence

Net versus combinatory effects of firm and industry antecedents of sales growth

This study examines antecedents of sales growth using a two-step mixed-method approach including analyses of net effects and combinatory effects. Based on a sample of 453 respondents from manufacturing and service firms, this article shows how the combination of structural equation modeling (SEM) and fuzzy set Qualitative Comparative Analysis (fsQCA) provides more detailed insights into the causal patterns of factors to explain sales growth. This article contributes to the extant literature by highlighting fsQCA as a useful method to analyze complex causality (specifically combinatory effects of antecedent conditions) and by discussing options regarding how this approach can be used to complement findings from conventional causal data analysis procedures that analyze net effects

Exploring the topology of the plausible: Fs/QCA counterfactual analysis and the plausible fit of unobserved organizational configurations

The main aim of this contribution is to expand the dominant rationale of organizational design research by including solutions and possibilities not observed in reality. We believe that the counterfactual approach to configurations responds to an open call in organization theory and strategy to move the modelling of fit towards a more robust and theory-based specification. With this new approach we propose to rediscover the roots of organization design as a distinct normative discipline that ‘should stand approximately in relation to the basic social sciences as engineering stands with respect to physical sciences or medicine to the biological’. At a more general level, our view implies an expansion of the dominant meaning of the concept of ‘relevance’ in management research. While we agree with Gulati (2007: 780) that we as scholars should probe ‘more deeply into the problems and other issues that managers care about’, we also believe that relevance does not necessarily mean that researchers have to use an ex-post rationality by studying only empirically frequent phenomena. In contrast, we think that any management esearcher should bring with her or himself a fragment of the spirit of the great Greek philosopher Anaximander (c. 610–c. 546 BC), who foresaw the concept of the infinite universe without the support of any empirical observation and against the predominant wisdom of the time. Not by chance, Karl Popper (1998) onsidered Anaximander’s intuitions among the most vivid demonstrations of the power of human thought and logic

Embelin binds to human neuroserpin and impairs its polymerisation

Neuroserpin (NS) is a serpin inhibitor of tissue plasminogen activator (tPA) in the brain. The polymerisation of NS pathologic mutants is responsible for a genetic dementia known as familial encephalopathy with neuroserpin inclusion bodies (FENIB). So far, a pharmacological treatment of FENIB, i.e. an inhibitor of NS polymerisation, remains an unmet challenge. Here, we present a biophysical characterisation of the effects caused by embelin (EMB a small natural compound) on NS conformers and NS polymerisation. EMB destabilises all known NS conformers, specifically binding to NS molecules with a 1:1 NS:EMB molar ratio without unfolding the NS fold. In particular, NS polymers disaggregate in the presence of EMB, and their formation is prevented. The NS/EMB complex does not inhibit tPA proteolytic activity. Both effects are pharmacologically relevant: firstly by inhibiting the NS polymerisation associated to FENIB, and secondly by potentially antagonizing metastatic processes facilitated by NS activity in the brain

A Cognitive Mapping Approach to Business Models: Representing Causal Structures and Mechanisms

Research has highlighted the cognitive nature of the business model intended as a cognitive representation describing a business’ value creation and value capture activities. Whereas the content of the business model has been extensively investigated from this perspective, less attention has been paid to the business model’s causal structure – i.e. the pattern of causeeffect relations that, in top managers’ or entrepreneurs’ understandings, link value creation and value capture activities. Building on the strategic cognition literature, this paper argues that conceptualizing and analyzing business models as cognitive maps can shed light on four important properties of a business model’s causal structure: the levels of complexity, focus, and clustering that characterize the causal structure; and the mechanisms underlying the causal links featured in that structure. I use examples of business models drawn from the literature as illustrations to describe these four properties. Finally, I discuss the value of a cognitive mapping approach for augmenting extant theories and practices of business model design

Profiling Dopamine-Induced Oxidized Proteoforms of β-synuclein by Top-Down Mass Spectrometry

The formation of multiple proteoforms by post-translational modifications (PTMs) enables a single protein to acquire distinct functional roles in its biological context. Oxidation of methionine residues (Met) is a common PTM, involved in physiological (e.g., signaling) and pathological (e.g., oxidative stress) states. This PTM typically maps at multiple protein sites, generating a heterogeneous population of proteoforms with specific biophysical and biochemical properties. The identification and quantitation of the variety of oxidized proteoforms originated under a given condition is required to assess the exact molecular nature of the species responsible for the process under investigation. In this work, the binding and oxidation of human β-synuclein (BS) by dopamine (DA) has been explored. Native mass spectrometry (MS) has been employed to analyze the interaction of BS with DA. In a second step, top-down fragmentation of the intact protein from denaturing conditions has been performed to identify and quantify the distinct proteoforms generated by DA-induced oxidation. The analysis of isobaric proteoforms is approached by a combination of electron-transfer dissociation (ETD) at each extent of modification, quantitation of methionine-containing fragments and combinatorial analysis of the fragmentation products by multiple linear regression. This procedure represents a promising approach to systematic assessment of proteoforms variety and their relative abundance. The method can be adapted, in principle, to any protein containing any number of methionine residues, allowing for a full structural characterization of the protein oxidation states

Dynamic Interchanging Native States of Lymphotactin Examined by SNAPP-MS

The human chemokine lymphotactin (Ltn) is a remarkable protein that interconverts between two unrelated native state structures in the condensed phase. It is possible to shift the equilibrium toward either conformation with selected sequence substitutions. Previous results have shown that a disulfide-stabilized variant preferentially adopts the canonical chemokine fold (Ltn10), while a single amino acid change (W55D) favors the novel Ltn40 dimeric structure. Selective noncovalent adduct protein probing (SNAPP) is a recently developed method for examining solution phase protein structure. Herein, it is demonstrated that SNAPP can easily recognize and distinguish between the Ltn10 and Ltn40 states of lymphotactin in aqueous solution. The effects of organic denaturants, acid, and disulfide bond reduction and blocking were also examined using SNAPP for the CC3, W55D, and wild type proteins. Only disulfide reduction was shown to significantly perturb the protein, and resulted in considerably decreased adduct formation consistent with loss of tertiary/secondary structure. Cold denaturation experiments demonstrated that wild-type Ltn is the most temperature sensitive of the three proteins. Examination of the higher charge states in all experiments, which are presumed to represent transition state structures between Ltn-10 and Ltn-40, reveals increased 18C6 attachment relative to the more folded structures. This observation is consistent with increased competitive intramolecular hydrogen bonding, which may guide the transition. Experiments examining the gas phase structures revealed that all three proteins can be structurally distinguished in the gas phase. In addition, the gas phase experiments enabled identification of preferred adduct binding sites