Справа Івана Дзюби

У статті автор, використовуючи документи Галузевого державного архіву СБ України, досліджує постать видатного літературознавця, громадського діяча Івана Дзюби у контексті боротьби співробітників органів держбезпеки УРСР з «українським буржуазним націоналізмом».В статье автор, используя документы Отраслевого государственного архива СБ Украины, исследует личность выдающегося литературоведа, общественного деятеля Ивана Дзюбы в контексте борьбы сотрудников органов госбезопасности УССР с «украинским буржуазным национализмом».Using the documents of State branch archive of State Security of Ukraine, the author investigates the personality of Ivan Dzyuba during the struggle of KGB of the UkSSR against the «Ukrainian bourgeois nationalism»

Quantitative Proteomics Illuminates a Functional Interaction between mDia2 and the Proteasome

Formin mDia2 is a cytoskeleton-regulatory protein that switches reversibly between a closed, autoinhibited and an open, active conformation. Although the open conformation of mDia2 induces actin assembly thereby controlling many cellular processes, mDia2 possesses also actin-independent and conformation-insensitive scaffolding roles related to microtubules and p53, respectively. Thus, we hypothesize that mDia2 may have other unappreciated functions and regulatory modes. Here we identify and validate proteasome and Ubiquitin as mDia2-interacting partners using stable isotope labeling with amino acids in cell culture-based quantitative proteomics and biochemistry, respectively. Although mDia2 is ubiquitinated, binds ubiquitinated proteins and free Ubiquitin, it is not a proteasome substrate. Surprisingly, knockdown of mDia2 increases the activity of the proteasome in vitro, whereas mDia2 overexpression has opposite effects only when it adopts the open conformation and cannot induce actin assembly. Consistently, a combination of candidate and unbiased proteome-wide analyses indicates that mDia2 regulates the cellular levels of proteasome substrate β-catenin and a number of ubiquitinated actin-regulatory proteins. Hence, these findings add more complexity to the mDia2 activity cycle by showing that the open conformation may control actin dynamics also through actin-independent regulation of the proteasome

Quantitative Proteomics Illuminates a Functional Interaction between mDia2 and the Proteasome

Formin mDia2 is a cytoskeleton-regulatory protein that switches reversibly between a closed, autoinhibited and an open, active conformation. Although the open conformation of mDia2 induces actin assembly thereby controlling many cellular processes, mDia2 possesses also actin-independent and conformation-insensitive scaffolding roles related to microtubules and p53, respectively. Thus, we hypothesize that mDia2 may have other unappreciated functions and regulatory modes. Here we identify and validate proteasome and Ubiquitin as mDia2-interacting partners using stable isotope labeling with amino acids in cell culture-based quantitative proteomics and biochemistry, respectively. Although mDia2 is ubiquitinated, binds ubiquitinated proteins and free Ubiquitin, it is not a proteasome substrate. Surprisingly, knockdown of mDia2 increases the activity of the proteasome in vitro, whereas mDia2 overexpression has opposite effects only when it adopts the open conformation and cannot induce actin assembly. Consistently, a combination of candidate and unbiased proteome-wide analyses indicates that mDia2 regulates the cellular levels of proteasome substrate β-catenin and a number of ubiquitinated actin-regulatory proteins. Hence, these findings add more complexity to the mDia2 activity cycle by showing that the open conformation may control actin dynamics also through actin-independent regulation of the proteasome

Quantitative Proteomics Illuminates a Functional Interaction between mDia2 and the Proteasome

Formin mDia2 is a cytoskeleton-regulatory protein that switches reversibly between a closed, autoinhibited and an open, active conformation. Although the open conformation of mDia2 induces actin assembly thereby controlling many cellular processes, mDia2 possesses also actin-independent and conformation-insensitive scaffolding roles related to microtubules and p53, respectively. Thus, we hypothesize that mDia2 may have other unappreciated functions and regulatory modes. Here we identify and validate proteasome and Ubiquitin as mDia2-interacting partners using stable isotope labeling with amino acids in cell culture-based quantitative proteomics and biochemistry, respectively. Although mDia2 is ubiquitinated, binds ubiquitinated proteins and free Ubiquitin, it is not a proteasome substrate. Surprisingly, knockdown of mDia2 increases the activity of the proteasome in vitro, whereas mDia2 overexpression has opposite effects only when it adopts the open conformation and cannot induce actin assembly. Consistently, a combination of candidate and unbiased proteome-wide analyses indicates that mDia2 regulates the cellular levels of proteasome substrate β-catenin and a number of ubiquitinated actin-regulatory proteins. Hence, these findings add more complexity to the mDia2 activity cycle by showing that the open conformation may control actin dynamics also through actin-independent regulation of the proteasome

The encephalomyocarditis virus Leader promotes the release of virions inside extracellular vesicles via the induction of secretory autophagy

Naked viruses can escape host cells before the induction of lysis via release in extracellular vesicles (EVs). These nanosized EVs cloak the secreted virus particles in a host-derived membrane, which alters virus-host interactions that affect infection efficiency and antiviral immunity. Currently, little is known about the viral and host factors regulating this form of virus release. Here, we assessed the role of the encephalomyocarditis virus (EMCV) Leader protein, a 'viral security protein' that subverts the host antiviral response. EV release upon infection with wildtype virus or a Leader-deficient mutant was characterized at the single particle level using high-resolution flow cytometry. Inactivation of the Leader abolished EV induction during infection and strongly reduced EV-enclosed virus release. We demonstrate that the Leader promotes the release of virions within EVs by stimulating a secretory arm of autophagy. This newly discovered role of the EMCV Leader adds to the variety of mechanisms via which this protein affects virus-host interactions. Moreover, these data provide first evidence for a crucial role of a non-structural viral protein in the non-lytic release of picornaviruses via packaging in EVs

The encephalomyocarditis virus Leader promotes the release of virions inside extracellular vesicles via the induction of secretory autophagy

Naked viruses can escape host cells before the induction of lysis via release in extracellular vesicles (EVs). These nanosized EVs cloak the secreted virus particles in a host-derived membrane, which alters virus-host interactions that affect infection efficiency and antiviral immunity. Currently, little is known about the viral and host factors regulating this form of virus release. Here, we assessed the role of the encephalomyocarditis virus (EMCV) Leader protein, a 'viral security protein' that subverts the host antiviral response. EV release upon infection with wildtype virus or a Leader-deficient mutant was characterized at the single particle level using high-resolution flow cytometry. Inactivation of the Leader abolished EV induction during infection and strongly reduced EV-enclosed virus release. We demonstrate that the Leader promotes the release of virions within EVs by stimulating a secretory arm of autophagy. This newly discovered role of the EMCV Leader adds to the variety of mechanisms via which this protein affects virus-host interactions. Moreover, these data provide first evidence for a crucial role of a non-structural viral protein in the non-lytic release of picornaviruses via packaging in EVs

Novel Hsp90 partners discovered using complementary proteomic approaches

Hsp90 is an essential eukaryotic molecular chaperone that stabilizes a large set of client proteins, many of which are involved in various cellular signaling pathways. The current list of Hsp90 interactors comprises about 200 proteins and this number is growing steadily. In this paper, we report on the application of three complementary proteomic approaches directed towards identification of novel proteins that interact with Hsp90. These methods are coimmunoprecipitation, pull down with biotinylated geldanamycin, and immobilization of Hsp90β on sepharose. In all, this study led to the identification of 42 proteins, including 18 proteins that had not been previously characterized as Hsp90 interactors. These novel Hsp90 partners not only represent abundant protein species, but several proteins were identified at low levels, among which signaling kinase Cdk3 and putative transcription factor tripartite motif-containing protein 29. Identification of tetratricopeptide-repeat-containing mitochondrial import receptor protein Tom34 suggests the involvement of Hsp90 in the early steps of translocation of mitochondrial preproteins. Taken together, our data expand the knowledge of the Hsp90 interactome and provide a further step in our understanding of the Hsp90 chaperone system

On terminal alkynes that can react with active-site cysteine nucleophiles in proteases

Active-site directed probes are powerful in studies of enzymatic function. We report an active-site directed probe based on a warhead so far considered unreactive. By replacing the C-terminal carboxylate of ubiquitin (Ub) with an alkyne functionality, a selective reaction with the active-site cysteine residue of de-ubiquitinating enzymes was observed. The resulting product was shown to be a quaternary vinyl thioether, as determined by X-ray crystallography. Proteomic analysis of proteins bound to an immobilized Ub alkyne probe confirmed the selectivity toward de-ubiquitinating enzymes. The observed reactivity is not just restricted to propargylated Ub, as highlighted by the selective reaction between caspase-1 (interleukin converting enzyme) and a propargylated peptide derived from IL-1β, a caspase-1 substrate