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Starvation in bacteria is a complex adaptive response to deprivation of nutrients that has been shown to implicate a number of stress networks that modulate pathogenicity and antibiotic resistance. Starvation in nature is qualitatively different from in-culture late stationary phase energy source depletion. To look into proteome-level alterations elicited by complete elimination of carbon source, we used Escherichia coli HT115-derived SLE1 strain cells and a combination of label-free and metabolic isotope labeling approaches. We isolated pathways differentially affected by carbon starvation and observed robust upregulation of proteins implicated in networks belonging to Gene Ontology terms 'Biological adhesion' and 'Methylglyoxal metabolic process'.

Rapalogs have become standard-of-care in patients with metastatic breast, kidney, and neuroendocrine cancers. Nevertheless, tumor escape occurs after several months in most patients, highlighting the need to understand mechanisms of resistance. Using a panel of cancer cell lines, we show that rapalogs downregulate the putative protein kinase TRIB3 (tribbles pseudokinase 3). Blood samples of a small cohort of patients with cancer treated with rapalogs confirmed downregulation of TRIB3. Downregulation of TRIB3 was mediated by LRRFIP1 independently of mTOR and disrupted its interaction with the spliceosome, where it participated in rapalog-induced deregulation of RNA splicing. Conversely, overexpression of TRIB3 in a panel of cancer cell lines abolished the cytotoxic effects of rapalogs. These findings identify TRIB3 as a key component of the spliceosome, whose repression contributes significantly to the mechanism of resistance to rapalog therapy. Significance: Independent of mTOR signaling, rapalogs induce cytoxicity by dysregulating spliceosome function via repression of TRIB3, the loss of which may, in the long term, contribute to therapeutic resistance.

Analysis of large-scale interphase genome positioning with reference to a nuclear landmark has recently been studied using sequencing-based single cell approaches. However, these approaches are dependent upon technically challenging, time consuming and costly high throughput sequencing technologies, requiring specialized bioinformatics tools and expertise. Here, we propose a novel, affordable and robust microscopy-based single cell approach, termed Topokaryotyping, to analyze and reconstruct the interphase positioning of genomic loci relative to a given nuclear landmark, detectable as banding pattern on mitotic chromosomes. This is accomplished by proximity-dependent histone labeling, where biotin ligase BirA fused to nuclear envelope marker Emerin was coexpressed together with Biotin Acceptor Peptide (BAP)-histone fusion followed by (i) biotin labeling, (ii) generation of mitotic spreads, (iii) detection of the biotin label on mitotic chromosomes and (iv) their identification by karyotyping. Using Topokaryotyping, we identified both cooperativity and stochasticity in the positioning of emerin-associated chromatin domains in individual cells. Furthermore, the chromosome-banding pattern showed dynamic changes in emerin-associated domains upon physical and radiological stress. In summary, Topokaryotyping is a sensitive and reliable technique to quantitatively analyze spatial positioning of genomic regions interacting with a given nuclear landmark at the single cell level in various experimental conditions.

Introduction The human genome consists of roughly 30,000 genes coding for over 500,000 different proteins, of which more than 10,000 proteins can be produced by the cell at any given time (the cellular “proteome”). It has been estimated that over 80% of proteins do not operate alone, but in complexes. These protein-protein interactions (PPI) are regulated by several mechanisms. For example, post-translational modifications (methylation, acetylation, phosphorylation, or ubiquitination) or metal-binding can lead to conformational changes that alter the affinity and kinetic parameters of the interaction. Many PPIs are part of larger cellular networks of interactions or interactomes. Indeed, these interactions are at the core of the entire interactomics system of any living cell, and so, aberrant PPIs are the basis of multiple diseases, such as neurodegenerative diseases and cancer. The objective of this study was to develop a method of monitoring protein-protein interactions and proximity dependence in vivo. Methods The biotin ligase BirA was fused to the protein of interest, and the Biotin Acceptor Peptide (BAP) was fused to an interacting partner to make the detection of its biotinylation possible by western blot or mass spectrometry. Results Using several experimental systems (BirA.A + BAP.B), we showed that the biotinylation is interaction/proximity dependent. Here, A and B are the next nuclear proteins used in the experiments – 3 paralogues of heterochromatin protein HP1α (CBX5), HP1β (CBX1), HP1γ (CBX3), wild type and transcription mutant factor Kap1, translesion DNA polymerase PolH and E3, ubiquitin ligase RAD18, Proliferative Cell Nuclear Antigen (PCNA), ubiquitin Ub, SUMO-2/3, different types and isoforms of histones H2A, H2Az, H3.1, H3.3, CenpA, H2A.BBD, and macroH2A. The variant of this approach is termed PUB-NChIP (Proximity Utilizing Biotinylation with Native Chromatin Immuno-precipitation) and is designed to purify and study the protein composition of chromatin in proximity to the nuclear protein of interest. Using the RAD18 protein as a model, we demonstrated that the RAD18-proximal chromatin is enriched in some H4 acetylated species. Moreover, the RAD18-proximal chromatin containing a replacement histone H2Az has a different pattern of H4 acetylation. Conclusion Progress in the last decade in cancer drug therapy has led us to the conclusion that the nucleus of eukaryotic cells is an active site for many cellular processes important to the development of cancer. These processes include changes in genetic and epigenetic landscape (e. g. methylation of DNA, modification of histones) and the expression levels of transcription factors, which regulates gene products (e.g. hypoxia-inducible factor 1α (HIF-1α) in chronic anemia, etc.) where protein-protein interactions play important role. Understanding the nature of protein-protein interactions may improve design strategies for small-molecule PPI modulators. PPI assay technologies that closely reflect physiological conditions hold the key to developing specific anti-cancer drugs.

Our recent studies have revealed the early up-regulated expression of interferon alpha (IFNα) in the liver, induced by partial hepatectomy. The role of this cytokine of innate immune response in liver regeneration is still controversial. Aim. To analyze expression of canonical interferon-stimulated genes Ube1l, Ube2l6, Trim25, Usp18 and Isg15 during the liver transition from quiescence to proliferation induced by partial hepatectomy, and acute phase response induced by laparotomy. These genes are responsible for posttranslational modification of proteins by ISGylation. The expression of genes encoding TATA binding protein (TBP) and 18S rRNA served as indirect general markers of transcriptional and translational activities. Methods. The abundance of investigated RNAs was assessed in total liver RNA by real time RT–qPCR. Results. Partial hepatecomy induced steady upregulation of the Tbp and 18S rRNA genes expression during 12 hours post-surgery and downregulation or no change in expression of ISGylation-related genes during the first 3 hours followed by slight upregulation at 12 hours. The level of Isg15 transcripts was permanently below that of the control during the prereplicative period. Laparotomy induced a continuous downregulation of Tbp and 18S rRNA expression and early (1–3h) upregulation of ISGylation–related transcripts followed by a sharp drop at 6 hours and slight increase/decrease at 12 hours. The changes in the abundance of Ifnα and ISGylation-related mRNAs were oppositely directed at each stage of the response to partial hepatectomy and laparotomy. Conclusion. We suggest that the expression of ISGylation-related genes does not depend on the expression of Ifnα gene after both surgeries. The indirect indices of transcription and translation as well as the expression of ISGylation-relaled genes are principally different in response to partial hepatectomy and laparotomy and argue for the high specificity of innate immune response. Наші нещодавні дослідження показали, що на ранньому етапі відновлювального процесу активується синтез інтерферону α (IFNα), цитокина вродженого імунітету. Роль IFNα в процесі відновлення печінки поки що не з’ясована. Мета. Проаналізувати експресію класичних інтерферон-стимульованих генів (ІСГ), Ube1l, Ube2l6, Trim25, Usp18 і Isg15, в печінці під час її переходу від стану спокою до проліферації у відповідь на часткову гепатектомію й під час реакції гострої фази після лапаротомії. Ці гени відповідають за посттрансляційну модифікацію білків шляхом ІСГілювання. Рівень експресії генів, які кодують 18S рРНК і транскрипційний фактор TBP, що зв’язується з TATA-боксом, використали в якості непрямого показника інтенсивності трансляції і транскрипції. Методи. Концентрацію індивідуальних РНК визначали в тотальній РНК печінки методом зворотної транскрипції і ланцюгової полімеризації в реальному часі. Результати. Часткова гепатектомія викликає поступове підвищення експресії генів Tbp і 18S rRNA впродовж 12 год. після операції і зниження експресії генів ІСГілювання впродовж перших трьох годин з наступним незначним підвищенням до 12 год. Рівень Isg15 транскриптів залишається зниженим впродовж всього періоду дослідження. Лапаротомія викликає поступове зниження експресії генів Tbp і 18S rRNA і виражене підвищення концентрації транскриптів генів ІСГілювання на першому етапі (1–3 год.), що змінюється різким зниженням до 6-ої год. з наступним незначним підвищенням/зниженням до 12-ої год. Зміни в рівні транскриптів гена Ifnα і генів системи ІСГілювання носять протилежний характер на кожній із стадій відповіді печінки на часткову гепатектомію і лапаротомію. Висновки. Припускаємо, що експресія генів, які задіяні в процесі ІСГілювання, не залежить від експресії гена Ifnα. Використані «показники» активності транскрипції, трансляції і посттрансляційної модифікації білків шляхом ІСГілювання принципово відрізняються між двома реакціями відповіді печінки на часткову гепатектомію і лапаротомію, що свідчить про специфічність реакцій вродженого імунітету. Наши недавние исследования показали, что после частичной гепатэктомии на раннем этапе восстановительного процесса активируется синтез интерферона альфа (IFNα), цитокина в системе врожденного иммунитета. Роль IFNα в процессе регенерации пока не ясна. Цель. Проанализировать экспрессию классических интерферон-стимулируемых генов Ube1l, Ube2l6, Trim25, Usp18 и Isg15 в процессе перехода печени из состояния покоя к пролиферации в ответ на частичную гепатектомию и во время реакции острой фазы после лапаротомии. Эти гены ответственны за посттрансляционную модификацию белков путем ИСГилирования. Уровень экспрессии генов, которые кодируют транскрипционный фактор TBP и 18S рРНК, использовали в качестве непрямого показателя интенсивности транскрипции и трансляции. Методы. Концентрацию исследуемых РНК определяли в тотальной РНК печени методом обратной транскрипции и цепной полимеризации в реальном времени. Результаты. Частичная гепатэктомия вызывает постепенное повышение экспрессии генов Tbp и 18S rRNA в течение 12 час после операции и снижение экспрессии генов ИСГилирования в период 1–3 ч с последующим незначительным повышением к 12 ч. Уровень Isg15 транскриптов неизменно снижен в течении всего исследуемого периода. Лапаротомия вызывает постепенное снижение экспрессии генов Tbp и 18S rRNA и выраженное повышение концентрации транскриптов генов, участвующих в ИСГилировании (1–3 ч), которое сменяется резким снижением к 6 ч и последующим незначительным повышением/снижением к 12 ч. Изменения в уровнях транскриптов Ifnα и транскриптов генов системы ИСГилирования носят разнонаправленный характер на каждой из стадий ответа печени на частичную гепатэктомию и лапаротомию. Выводы. Предполагаем, что экспрессия генов, определяющих ИСГилирование, не зависит от экспрессии гена Ifnα. Использованные «показатели» активности процессов транскрипции, трансляции и посттрансляционной модификации белков путем ИСГилирования в ответ на частичную гепатэктомию и лапаротомию принципиально различны и свидетельствуют в пользу специфичности реакций врожденного иммунитета.

The nucleotidyl cyclase toxin ExoY is one of the virulence factors injected by the Pseudomonas aeruginosa type III secretion system into host cells. Inside cells, it is activated by an unknown eukaryotic cofactor to synthesize various cyclic nucleotide monophosphates. ExoY-like adenylate cyclases are also found in Multifunctional-Autoprocessing Repeats-in-ToXin (MARTX) toxins produced by various Gram-negative pathogens. Here we demonstrate that filamentous actin (F-actin) is the hitherto unknown cofactor of ExoY. Association with F-actin stimulates ExoY activity more than 10,000 fold in vitro and results in stabilization of actin filaments. ExoY is recruited to actin filaments in transfected cells and alters F-actin turnover. Actin also activates an ExoY-like adenylate cyclase MARTX effector domain from Vibrio nigripulchritudo. Finally, using a yeast genetic screen, we identify actin mutants that no longer activate ExoY. Our results thus reveal a new sub-group within the class II adenylyl cyclase family, namely actin-activated nucleotidyl cyclase (AA-NC) toxins., The ExoY toxin is injected by Pseudomonas aeruginosa into host cells, where it is activated by an unknown host factor. Here the authors identify such factor as filamentous actin.

The Epstein-Barr virus nuclear antigen leader protein (EBNA-LP) acts as a co-activator of EBNA-2, a transcriptional activator essential for Epstein-Barr virus (EBV)-induced B-cell transformation. Burkitt’s lymphoma (BL) cells harboring a mutant EBV strain that lacks both the EBNA-2 gene and 3′ exons of EBNA-LP express Y1Y2-truncated isoforms of EBNA-LP (tEBNA-LP) and better resist apoptosis than if infected with the wild-type virus. In such BL cells, tEBNA-LP interacts with the protein phosphatase 2A (PP2A) catalytic subunit (PP2A C), and this interaction likely plays a role in resistance to apoptosis. Here, 28 cellular and four viral proteins have been identified by mass spectrometry as further possible interactors of tEBNA-LP. Three interactions were confirmed by immunoprecipitation and Western blotting, namely with the A structural subunit of PP2A (PP2A A), the structure-specific recognition protein 1 (SSRP1, a component of the facilitate chromatin transcription (FACT) complex), and a new form of the transcription factor EC (TFEC). Thus, tEBNA-LP appears to be involved not only in cell resistance to apoptosis through its interaction with two PP2A subunits, but also in other processes where its ability to co-activate transcriptional regulators could be important.

The H3.3 histone variant has been a subject of increasing interest in the field of chromatin studies due to its two distinguishing features. First, its incorporation into chromatin is replication independent unlike the replication-coupled deposition of its canonical counterparts H3.1/2. Second, H3.3 has been consistently associated with an active state of chromatin. In accordance, this histone variant should be expected to be causally involved in the regulation of gene expression, or more generally, its incorporation should have downstream consequences for the structure and function of chromatin. This, however, leads to an apparent paradox: In cells that slowly replicate in the organism, H3.3 will accumulate with time, opening the way to aberrant effects on heterochromatin. Here, we review the indications that H3.3 is expected both to be incorporated in the heterochromatin of slowly replicating cells and to retain its functional downstream effects. Implications for organismal aging are discussed.

Gene positioning in the nucleus plays an important role in gene activity and genome stability, both in norm and pathology. We propose a new principle for the analysis of the large scale chromatin organization at the single-cell level, termed Topokaryotyping. It is based on coexpression in cells of (i) biotin ligase BirA targeted to a particular intranuclear domain (via its fusion with a protein-marker of this domain) together with (ii) BAP-histone fusion. The application of biotin pulse chase followed by (i) generation of mitotic spreads, (ii) detection of the biotin label and (iii) karyotyping technique to identify the chromosomes should provide information on the association of particular chromosome regions with the nuclear domain under study. We discuss potential advantages of the proposed approach as compared to other methods to study genome topology in the nucleus. Позиція генів в ядрі критична для їх функціонування та стабільності геному, в нормальних і патологічних станах клітини. Ми пропонуємо новий принцип аналізу організації хроматину на ядерному рівні в індивідуальних клітках, званий Топокаріотіпірованіе. Він заснований на спільній експресії в клітинах (i) Біотин лігази BirA локалізованої в конкретному ядерному домені (за рахунок її фузірованія (злиття) з білком-маркером цього домену) і (ii) гістонові гена злитого з BAP доменом (пептидом-акцептором біотину). Мічення клітин біотином і їх подальша відмивання, за якою слідують (i) створення препаратів метафазних хромосом, (ii) детектування біотіновой мітки на хромосомах і (iii) каріотипування з метою ідентифікації хромосом - повинні надати інформацію про асоціацію даного хромосомного регіону з досліджуваним ядерним доменом. Ми обговорюємо потенційні переваги запропонованого методу з іншими підходами до вивчення топології генома в клітинному ядрі. Позиция генов в ядре критична для их функционирования и стабильности генома, в нормальных и патологических состояниях клетки. Мы предлагаем новый принцип анализа организации хроматина на ядерном уровне в индивидуальых клетках, называемый Топокариотипирование. Он основан на совместной экспрессии в клетках (i) Биотин лигазы BirA локализованной в конкретном ядерном домене (за счет ее фузирования (слияния) с белком-маркером этого домена) и (ii) гистонового гена слитого с BAP доменом (пептидом-акцептором биотина). Мечение клеток биотином и их последующая отмывка, за которой следуют (i) создание препаратов метафазных хромосом, (ii) детектирование биотиновой метки на хромосомах и (iii) кариотипирование с целью идентификации хромосом – должны предоставить информацию об ассоциации данного хромосомного региона с исследуемым ядерным доменом. Мы обсуждаем потенциальные достоинства предлагаемого метода с другими подходами к изучению топологии генома в клеточном ядре.

Epigenetics has captured the attention of scientists in the past decades, yet its scope has been continuously changing. In this paper, we give an overview on how and why its definition has evolved and suggest several clarification on the concepts used in this field. Waddington coined the term in 1942 to describe genes interaction with each other and with their environment and insisted on dissociating these events from development. Then, Holliday and others argued that epigenetic phenomena are characterized by their heritability. However, differentiated cells can maintain their phenotypes for decades without undergoing division, which points out the limitation of the «heritability» criterion for a particular phenomenon to qualify as epigenetic. «Epigenetic stability» encompasses traits preservation in both dividing and non dividing cells. Likewise, the use of the term «epigenetic regulation» has been misleading as it overlaps with «regulation of gene expression», whereas «epigenetic information» clearly distinguishes epigenetic from genetic phenomena. Consequently, how could epigenetic information be transmitted and perpetuated? The term «epigenetic templating» has been proposed to refer to a general mechanism of perpetuation of epigenetic information that is based on the preferential activity of enzymes that deposit a particular epigenetic mark on macromolecular complexes already containing the same mark. Another issue that we address is the role of epigenetic information. Not only it is important in allowing alternative interpretations of genetic information, but it appears to be important in protecting the genome, as can be illustrated by bacterial endonucleases that targets non methylated DNA – i. e. foreign DNA – and not the endogenous methylated DNA. Епігенетика привертає увагу вчених уже декілька десятиліть, але значення вкладеного в неї сенсу постійно змінюється. Ми обговорюємо причини таких змін і пропонуємо декількя пояснювальних коментарів. Уоддингтон увів термін «епігенетика» в 1942 році для описання взаємодії генів, важливих для розвитку організму, між собою та з навколишнім середовищем. Надалі Холлідей та інші наполягали на понятті «успадковуваності» як необхідній характеристиці епігенетичних явищ. Однак диференційовані клітини зберігають свої фенотипи протягом десятиліть і при цьому не діляться, що вказує на обмеженість «успадковуваності» як критерію того, щоб певне явище розглядати як епігенетичне. «Епігенетична стабільність» запропонована як більш загальне поняття, яке означає збереження характеристик в обох клітинах: які ділять і не діляться. З іншого боку, термін «епігенетична регуляція» призводить до плутанини, оскільки його значення суттєво перекривається або навіть повністю збігається за змістом з виразом «регуляція експресії генів», тоді як «епігенетична інформація» чітко розмежовує епігенетичні і генетичні явища. І постає питання, яким чином епігенетична інформація може відтворюватися? Ми запропонували термін «epigenetic templating» для визначення механізму відтворення епігенетичної інформації, заснованого на тому, що ферменті, які ставлять певну епігенетичну мітку, віддають перевагу макромолекулярним субстратам, які вже містать подібну мітку. Нарешті ми торкаємось питання щодо ролі епігенетичної інформації. Вона потрібна не лише для альтернативних інтерпретацій генетичної інформації, але й для захисту геному, як це проілюстровано нами на прикладі бактерійних ендонуклеаз, які атакують неметильовану (тобто чужорідну) ДНК і не пошкоджують метильованої (тобто власної) ДНК. Эпигенетика привлекaет внимание ученых уже несколько десятилетий, но значение вкладываемого в нее смысла постоянно меняется. Мы обсуждаем причины таких изменений и предлагаем не- сколько поясняющих комментариев. Уоддингтон ввел термин «эпигенетика» в 1942 году для описания взаимодействия генов, важных для развития организма, друг с другом и с окружающей средой. Позже Холлидей и другие настаивали на понятии «наследуемости» как необходимой характеристике эпигенетических явлений. Однако дифференцированные клетки сохраняют свои фенотипы на протяжении десятилетий и при этом не делятся, что указывает на ограниченность «наследуемости» как критерия того, чтобы определенное явление рассматривать как эпигенетическое. «Эпигенетическая стабильность» предложена как более общее понятие, означающее сохранение характеристик в обеих делящихся и не делящихся клетках. С другой стороны, термин «эпигенетическая регуляция» ведет к путанице, поскольку его значение сильно перекрывается или даже совпадает по смыслу с выражением «регуляция экспрессии генов», в то время как «эпигенетическая информация» четко разграничивает эпигенетические и генетические явления. Далее следует вопрос, каким образом эпигенетическая информация может воспроизводиться? Мы предложили термин «epigenetic templating» для обозначения механизма воспроизведения эпигенетической информации, основанного на том, что ферменты, ставящие определенную эпигенетическую метку, предпочтают макромолекулярные субстраты, уже содержащие подобную метку. Наконец, мы касаемся вопроса о роли эпигенетической информации. Она нужна не только для альтернативных интерпретаций генетической информации, но и для защиты генома, как это проиллюстрировано нами на примере бактериальных эндонуклеаз, атакующих неметилированную (то есть чужеродную) ДНК и не повреждающих метилированной (то есть своей) ДНК.

Variation in chromatin composition and organization often reflects differences in genome function. Histone variants, for example, replace canonical histones to contribute to regulation of numerous nuclear processes including transcription, DNA repair, and chromosome segregation. Here we focus on H2A.Bbd, a rapidly evolving variant found in mammals but not in invertebrates. We report that in human cells, nucleosomes bearing H2A.Bbd form unconventional chromatin structures enriched within actively transcribed genes and characterized by shorter DNA protection and nucleosome spacing. Analysis of transcriptional profiles from cells depleted for H2A.Bbd demonstrated widespread changes in gene expression with a net downregulation of transcription and disruption of normal mRNA splicing patterns. In particular, we observed changes in exon inclusion rates and increased presence of intronic sequences in mRNA products upon H2A.Bbd depletion. Taken together, our results indicate that H2A.Bbd is involved in formation of a specific chromatin structure that facilitates both transcription and initial mRNA processing.

Recombinant-tagged proteins have a widespread use in experimental research as well as in clinical diagnostic and therapeutic approaches. Well-stocked sets of differently tagged variants of a same protein would be of great help. However, the construction of differently tagging vectors is a demanding task since cloning procedures need several tailored DNA inserts. In this study, we describe a novel vector system that allows a cost- and time-effective production of differently tagged variants of a same protein by using the same DNA fragment and a set of vectors each carrying a different tag. The design of these expression vectors is based on an intronic region that becomes functional upon cloning the insert sequence, splicing of which attaches a certain tag to the protein termini. This strategy allows for the cloning of the fragment that codes for the protein of interest, without any further modification, into different vectors, previously built and ready-to-use, each carrying a tag that will be joined to the protein. Proof of principle for our expression system, presented here, is shown through the production of a functional anti-GD2 Fab fragment tagged with biotin or polyhistidine, or a combination of both, followed by the demonstration of the functional competencies of both the protein and the tags.

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant hereditary neuromuscular disorder. The clinical features of FSHD include weakness of the facial and shoulder girdle muscles followed by wasting of skeletal muscles of the pelvic girdle and lower extremities. Although FSHD myoblasts grown in vitro can be induced to differentiate into myotubes by serum starvation, the resulting FSHD myotubes have been shown previously to be morphologically abnormal. Aim. In order to find the cause of morphological anomalies of FSHD myotubes we compared in vitro myogenic differentiation of normal and FSHD myoblasts at the protein level. Methods. We induced myogenic differentiation of normal and FSHD myoblasts by serum starvation. We then compared protein extracts from proliferating myoblasts and differentiated myotubes using SDS-PAGE followed by mass spectrometry identification of differentially expressed proteins. Results. We demonstrated that the expression of vimentin was elevated at the protein and mRNA levels in FSHD myotubes as compared to normal myotubes. Conclusions. We demonstrate for the first time that in contrast to normal myoblasts, FSHD myoblasts fail to downregulate vimentin after induction of in vitro myogenic differentiation. We suggest that vimentin could be an easily detectable marker of FSHD myotubes. Keywords: FSHD, vimentin, myogenic differentiation, proteomics. Плечо-лопатково-лицева м’язова дистрофія (міодистрофія Ландузі-Дежеріна) є аутосомним домінантно-успадковуваним нейром’язовим захворюванням. До клінічних ознак даного типу м’язової дистрофії належать слабкіть і атрофія лицевих м’язів плечового пояса, до яких на пізніших стадіях захворювання додаються м’язи пояса нижніх кінцівок. Незважаючи на те, що міобласти, виділені із хворих на міодистрофію Ландузі-Дежеріна, здатні до диференціювання in vitro, міотрубки, які виникли з них, мають низку морфологічних аномалій. Мета. Мета даної роботи полягає в пошуку причини морфологічних аномалій міотрубок пацієнтів з міодистрофією Ландузі-Дежеріна. Методи. Із використанням ростового середовища з низьким вмістом сироватки ми індукували м’язове диференціювання нормальних міобластів і міобластів пацієнтів з міодистрофією Ландузі-Дежеріна та проаналізували білковий склад міотрубок, які виникли з них, методом СДС-ПААГ з наступною ідентифікацією білків методом масс-спектрометрії. Результати. В представленій роботі вперше показано, що в міотрубках пацієнтів з міодистрофією Ландузі-Дежеріна підвищена експресія гена віментину. Висновки. Віментин можна застосовувати як ген – маркер міотрубок хворих на міодистрофію Ландузі-Дежеріна. Ключові слова: міодистрофія Ландузі-Дежеріна, віментин, м’язове диференціювання, протеоміка. Лице-лопаточно-бедренная мышечная дистрофия (миодистрофия Ландузи-Дежерина) является аутосомным доминантно-наследуемым нейромышечным заболеванием. Клиническая картина данного типа мышечной дистрофии включает слабость и атрофию лицевых мышц и мышц плечевого пояса, к которым на более поздних стадиях заболевания добавляются мышцы пояса нижних конечностей. Несмотря на то, что миобласты, выделенные из больных миодистрофией Ландузи-Дежерина, способны к дифференцировке in vitro, возникающие из них миотрубки имеют ряд морфологических аномалий. Цель. Целью данной работы является поиск причины морфологических аномалий миотрубок пациентов с миодистрофией Ландузи-Дежерина. Методы. Используя ростовую среду с низким содержанием сыворотки, мы индуцировали мышечную дифференцировку нормальных миобластов и миобластов пациентов с миодистрофией Ландузи-Дежерина и проанализировали белковый состав возникших из них миотрубок методом СДС-ПААГ с последующей идентификацией белков методом масс-спектрометрии. Результаты. В данной работе впервые показано, что в миотрубках пациентов с миодистрофией Ландузи-Дежерина увеличена экспрессия гена виментина. Выводы. Виментин может быть использован в качестве гена – маркера миотрубок больных миодистрофией Ландузи-Дежерина. Ключевые слова: миодистрофия Ландузи-Дежерина, виментин, мышечная дифференцировка, протеомика.

The common techniques to study protein-protein proximity in vivo are not well adapted to the capabilities and the expertise of a standard proteomics laboratory, typically based on the use of mass spectrometry. With the aim of closing this gap, we have developed PUB-MS (for proximity utilizing biotinylation and mass spectrometry), an approach to monitor protein-protein proximity, based on biotinylation of a protein fused to a biotin-acceptor peptide (BAP) by a biotin-ligase, BirA, fused to its interaction partner. The biotinylation status of the BAP can be further detected by either Western analysis or mass spectrometry. The BAP sequence was redesigned for easy monitoring of the biotinylation status by LC-MS/MS. In several experimental models, we demonstrate that the biotinylation in vivo is specifically enhanced when the BAP- and BirA-fused proteins are in proximity to each other. The advantage of mass spectrometry is demonstrated by using BAPs with different sequences in a single experiment (allowing multiplex analysis) and by the use of stable isotopes. Finally, we show that our methodology can be also used to study a specific subfraction of a protein of interest that was in proximity with another protein at a predefined time before the analysis.

Protein footprinting is a new methodology that is based on probing, typically with the use of MS, of reactivity of different amino acid residues to a modifying reagent. Data thus obtained allow one to make inferences about protein conformations and their intermolecular interactions. Most of the protein footprinting studies so far have been performed on individual proteins in vitro. We explore whether a similar approach is possible with the proteins inside of living cells, employing dimethylsulfate (DMS), a reagent widely used for the in vivo footprinting of nucleic acids. DMS can induce methylation of the lysine, histidine and glutamate residues on proteins. Using models of the histone H2B/H2AZ heterodimer assembled in vitro and from chromatin treated in vivo, we show that the methylation by deuterated DMS allows one to distinguish the accessibility of a particular residue in and out of the protein's environmental/structural context. The detection of changes in protein conformations or their interactions in vivo can provide a new approach to the identification of proteins involved in various intracellular pathways and help in the search for perspective drug targets and biomarkers of diseases.

Tumor-derived mutant forms of p53 compromise its DNA binding, transcriptional, and growth regulatory activity in a manner that is dependent upon the cell-type and the type of mutation. Given the high frequency of p53 mutations in human tumors, reactivation of the p53 pathway has been widely proposed as beneficial for cancer therapy. In support of this possibility p53 mutants possess a certain degree of conformational flexibility that allows for re-induction of function by a number of structurally different artificial compounds or by short peptides. This raises the question of whether physiological pathways for p53 mutant reactivation also exist and can be exploited therapeutically. The activity of wild-type p53 is modulated by various acetyl-transferases and deacetylases, but whether acetylation influences signaling by p53 mutant is still unknown. Here, we show that the PCAF acetyl-transferase is down-regulated in tumors harboring p53 mutants, where its re-expression leads to p53 acetylation and to cell death. Furthermore, acetylation restores the DNA-binding ability of p53 mutants in vitro and expression of PCAF, or treatment with deacetylase inhibitors, promotes their binding to p53-regulated promoters and transcriptional activity in vivo. These data suggest that PCAF-mediated acetylation rescues activity of at least a set of p53 mutations. Therefore, we propose that dis-regulation of PCAF activity is a pre-requisite for p53 mutant loss of function and for the oncogenic potential acquired by neoplastic cells expressing these proteins. Our findings offer a new rationale for therapeutic targeting of PCAF activity in tumors harboring oncogenic versions of p53.

We describe a modification of the TAP method for purification and analysis of multiprotein complexes, termed here DEF-TAP (for Differential Elution Fractionation after Tandem Affinity Purification). Its essential new feature is the use for last purification step of 6XHis-Ni++ interaction, which is resistant to a variety of harsh washing conditions, including high ionic strength and presence of organic solvents. This allows us to use various fractionation schemes before the protease digestion, which is expected to improve the coverage of the analysed protein mixture and also to provide an additional insight into the structure of the purified macromolecular complex and the nature of protein-protein interactions involved. We illustrate our new approach by analysis of soluble nuclear complexes containing histone H4 purified from HeLa cells. In particular, we observed different fractionation patterns of HAT1 and RbAp46 proteins as compared to RbAp48 protein, all identified as interaction partners of H4 histone. In addition, we report all components of the licensing MCM2-7 complex and the apoptosis-related DAXX protein among the interaction partners of the soluble H4. Finally, we show that HAT1 requires N-terminal tail of H4 for its stable association with this histone., 30 pages, 6 figures, 1 table

Tagging of proteins in vivo by covalent attachment of a biotin moiety has emerged as a new prospective tool for protein detection and purification. Previously, we established a strategy for expression of in vivo biotinylated proteins in mammalian cells. It is based on coexpression of the protein of interest fused to a short biotin acceptor peptide and biotin ligase BirA cloned in the same vector. We show here that the in vivo biotinylation can be used for immunogold postembedding labeling in immunoelectron microscopy experiments. We show that immunoelectron microscopy with biotinylated nuclear proteins is compatible with a wide range of postembedding methods, facilitating combination of morphological and localization studies in a single experiment. We also show that the method works in both transient transfection and stable cell line expression protocols and can be used for colocalization studies. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials. (J Histochem Cytochem 56:911–919, 2008)

Oligoribonuclease is the only RNase in Escherichia coli that is able to degrade RNA oligonucleotides five residues and shorter in length. Firmicutes including Bacillus subtilis do not have an Oligoribonuclease (Orn) homologous protein and it is not yet understood which proteins accomplish the equivalent function in these organisms. We had previously identified oligoribonucleases Orn from E. coli and its human homolog Sfn in a screen for proteins that are regulated by 3 0 -phosphoadenosine 5 0 -phosphate (pAp). Here, we identify YtqI as a potential functional analog of Orn through its interaction with pAp. YtqI degrades RNA oligonucleotides in vitro with preference for 3-mers. In addition, YtqI has pAp-phosphatase activity in vitro. In agreement with these data, YtqI is able to complement both orn and cysQ mutants in E. coli. An ytqI mutant in B. subtilis shows impairment of growth in the absence of cysteine, a phenotype resembling that of a cysQ mutant in E. coli. Phylogenetic distribution of YtqI, Orn and CysQ supports bifunctionality of YtqI.

Starvation is a complex adaptive response to insufficiency of nutrients that has been known to implicate a number of stress networks, and modulate pathogenicity and antibiotic resistance in bacteria. However, naturally occurring abrupt elimination of nutrients and prolonged periods of their complete absence, e.g. when bacteria are placed in natural or artificial water reservoirs, are qualitatively different from in-culture late stationary phase energy source diminution. Despite the obvious importance of proteomic investigation of bacteria exposed to nutrient deficiency, no comprehensive study on the subject has been published. In order to address the said shortage of knowledge, we decided to quantitatively look into the proteome-level alterations elicited by the complete lack of nutrients that constitute a viable source of carbon, i.e. carbon starvation, in the Escherichia coli HT115-derived SLE1 strain cells using the combination of label-free and SILAC-based proteomics. As a result, we obtained protein ratios for 1,757 and 1,241 protein groups for each technique respectively, 2D-annotated the quantifiable proteins present in both datasets, identified overand underrepresented Gene Ontology terms, and isolated protein groups ≥2-fold upand downregulated in response to carbon starvation (44 and 36 protein groups respectively). We observed upregulation of proteins implicated in various stress-related networks, most notably those that constitute the Gene Ontology term 'Biological adhesion', as well as various terms related to stress. Additionally, we identified several uncharacterized proteins, and our report is the first to ascribe them to a stress-induced proteome. Our data are available via ProteomeXchange with identifier PXD003255 and DOI:10.6019/PXD003255. INTRODUCTION Continuous development of mass spectra acquisition tools, in parallel with sophisticated bioinformatical data analysis environments, has ensured the rising popularity of mass spectrometry as a powerful technology for protein identification and quantification. Stable 10 11 12

Pseudomonas aeruginosa is a major cause of chronic infections in cystic fibrosis patients. The nucleotidyl cyclase toxin ExoY is a virulence factors injected by the pathogen and associated with severe damage to lung tissue. ExoY-like cyclases are also found in other Gram-negative pathogens and shown to contribute to virulence, although they remained poorly characterized. Here we demonstrate that filamentous actin (F-actin) is the hitherto unknown co-factor that activates P. aeruginosa ExoY within host target cells. Highly purified actin, when polymerized into filaments, potently stimulates (>10,000 fold) ExoY activity. ExoY co-localizes in vivo with actin filaments in transfected cells and, in vitro, it interferes with the regulation of actin assembly/disassembly-dynamics mediated by important F-actin-binding proteins. We further show that actin also activates an ExoY-like adenylate cyclase from a Vibrio species. Our results thus highlight a new sub-class within the class II adenylyl cyclase family, defined as actin-activated nucleotidyl cyclase (AA-NC) toxins.

Facioscapulohumeral dystrophy (FSHD) is an epi/genetic satellite disease associated with at least two satellite sequences in 4q35: (i) D4Z4 macrosatellite and (ii) β-satellite repeats (BSR), a prevalent part of the 4qA allele. Most of the recent FSHD studies have been focused on a DUX4 transcript inside D4Z4 and its tandem contraction in FSHD patients. However, the D4Z4-contraction alone is not pathological, which would also require the 4qA allele. Since little is known about BSR, we investigated the 4qA BSR functional role in the transcriptional control of the FSHD region 4q35. We have shown that an individual BSR possesses enhancer activity leading to activation of the Adenine Nucleotide Translocator 1 gene (ANT1), a major FSHD candidate gene. We have identified ZNF555, a previously uncharacterized protein, as a putative transcriptional factor highly expressed in human primary myoblasts that interacts with the BSR enhancer site and impacts the ANT1 promoter activity in FSHD myoblasts. The discovery of the functional role of the 4qA allele and ZNF555 in the transcriptional control of ANT1 advances our understanding of FSHD pathogenesis and provides potential therapeutic targets.

Introduction. The human genome consists of roughly 30,000 genes coding for over 500,000 different proteins, of which more than 10,000 proteins can be produced by the cell at any given time (the cellular “proteome”). It has been estimated that over 80% of proteins do not operate alone, but in complexes. These protein-protein interactions (PPI) are regulated by several mechanisms. For example, post-translational modifications (methylation, acetylation, phosphorylation, or ubiquitination) or metal-binding can lead to conformational changes that alter the affinity and kinetic parameters of the interaction. Many PPIs are part of larger cellular networks of interactions or interactomes. Indeed, these interactions are at the core of the entire interactomics system of any living cell, and so, aberrant PPIs are the basis of multiple diseases, such as neurodegenerative diseases and cancer. The objective of this study was to develop a method of monitoring protein-protein interactions and proximity dependence in vivo.Methods. The biotin ligase BirA was fused to the protein of interest, and the Biotin Acceptor Peptide (BAP) was fused to an interacting partner to make the detection of its biotinylation possible by western blot or mass spectrometry.Results. Using several experimental systems (BirA.A + BAP.B), we showed that the biotinylation is interaction/proximity dependent. Here, A and B are the next nuclear proteins used in the experiments – 3 paralogues of heterochromatin protein HP1a (CBX5), HP1b (CBX1), HP1g (CBX3), wild type and transcription mutant factor Kap1, translesion DNA polymerase PolH and E3, ubiquitin ligase RAD18, Proliferative Cell Nuclear Antigen (PCNA), ubiquitin Ub, SUMO-2/3, different types and isoforms of histones H2A, H2Az, H3.1, H3.3, CenpA, H2A.BBD, and macroH2A. The variant of this approach is termed PUB-NChIP (Proximity Utilizing Biotinylation with Native Chromatin Immuno-precipitation) and is designed to purify and study the protein composition of chromatin in proximity to the nuclear protein of interest. Using the RAD18 protein as a model, we demonstrated that the RAD18-proximal chromatin is enriched in some H4 acetylated species. Moreover, the RAD18-proximal chromatin containing a replacement histone H2Az has a different pattern of H4 acetylation.Conclusion. Progress in the last decade in cancer drug therapy has led us to the conclusion that the nucleus of eukaryotic cells is an active site for many cellular processes important to the development of cancer. These processes include changes in genetic and epigenetic landscape (e. g. methylation of DNA, modification of histones) and the expression levels of transcription factors, which regulates gene products (e.g. hypoxia-inducible factor 1α (HIF-1α) in chronic anemia, etc.) where protein-protein interactions play important role. Understanding the nature of protein-protein interactions may improve design strategies for small-molecule PPI modulators. PPI assay technologies that closely reflect physiological conditions hold the key to developing specific anti-cancer drugs.

Chromatin is considered to be a principal carrier of epigenetic information due to the ability of alternative chromatin states to persist through generations of cell divisions and to spread on DNA. Replacement histone variants are novel candidates for epigenetic marking of chromatin. We developed a novel approach to analyze the chromatin environment of nucleosomes containing a particular replacement histone. We applied it to human H2AZ, one of the most studied alternative histones. We find that neither H2AZ itself nor other features of the H2AZ-containing nucleosome spread to the neighboring nucleosomes in vivo, arguing against a role for H2AZ as a self-perpetuating epigenetic mark.

We identified Oligoribonuclease (Orn), an essential Escherichia coli protein and the only exonuclease degrading small ribonucleotides (5mer to 2mer) and its human homologue, small fragment nuclease (Sfn), in a screen for proteins that are potentially regulated by 3 0 -phosphoadenosine 5 0 -phosphate (pAp). We show that both enzymes are sensitive to micromolar amounts of pAp in vitro. We also demonstrate that Orn can degrade short DNA oligos in addition to its activity on RNA oligos, similar to what was documented for Sfn. pAp was shown to accumulate as a result of inhibition of the pAp-degrading enzyme by lithium, widely used to treat bipolar disorder, thus its regulatory targets are of significant medical interest. CysQ, the E.coli pAp-phosphatase is strongly inhibited by lithium and calcium in vitro and is a main target of lithium toxicity in vivo. Our findings point to remarkable conservation of the connection between sulfurand RNA metabolism between E.coli and humans.

Biotinylation of proteins is an attractive alternative to 'epitope-tagging', due to the strong biotin-(strept)avidin interaction and to the wide commercial availability of reagents for detection and purification of biotinylated macromolecules. Enzymatic biotinylation of target proteins in vivo using short biotin acceptor domains was described previously. Their use in mammalian cell requires expression of the bacterial biotinylation enzyme BirA. Here we describe the construction of a humanized version of BirA, with most of the rare codons replaced by codons that are more frequently used in human cells. The humanized BirA is expressed better in mammalian cells, resulting in improved efficiency of biotinylation in vivo. We anticipate that the humanized BirA gene will find use in many applications that involve in vivo biotinylation.

We describe a system designed to express biotinylated proteins in mammalian cells in vivo and its application to the study of protein-DNA interactions in vivo by chromatin immunoprecipitation (ChIP). The system is based on coexpression of the target protein fused to a short biotin acceptor domain together with the biotinylating enzyme BirA from Escherichia coli. The superior strength of the biotin-avidin interaction allows one to employ more stringent washing conditions in the ChIP protocol, resulting in a better signal/noise ratio.

Aims: The dual oxidase 2 (DUOX2) protein belongs to the NADPH oxidase (NOX) family. As H2O2 generator, it plays a key role in both thyroid hormone biosynthesis and innate immunity. DUOX2 forms with its maturation factor, DUOX activator 2 (DUOXA2), a stable complex at the cell surface that is crucial for the H2O2-generating activity, but the nature of their interaction is unknown. The contribution of some cysteine residues located in the N-terminal ectodomain of DUOX2 in a surface protein–protein interaction is suggested. We have investigated the involvement of different cysteine residues in the formation of covalent bonds that could be of critical importance for the function of the complex. Results: We report the identification and the characterization of an intramolecular disulfide bond between cys-124 of the N-terminal ectodomain and cys-1162 of an extracellular loop of DUOX2, which has important functional implications in both export and activity of DUOX2. This intramolecular bridge provides structural support for the formation of interdisulfide bridges between the N-terminal domain of DUOX2 and the two extracellular loops of its partner, DUOXA2. Innovation: Both stability and function of the maturation factor, DUOXA2, are dependent on the oxidative folding of DUOX2, indicating that DUOX2 displays a chaperone-like function with respect to its partner. Conclusions: The oxidative folding of DUOX2 that takes place in the endoplasmic reticulum (ER) appears to be a key event in the trafficking of the DUOX2/DUOXA2 complex as it promotes an appropriate conformation of the N-terminal region, which is propitious to subsequent covalent interactions with the maturation factor, DUOXA2. Antioxid. Redox Signal. 23, 724–733.

High mobility group nucleosome-binding (HMGN) proteins belong to a family of nuclear proteins that bind to nucleosomes and enhance transcription from chromatin templates by altering the structure of the chromatin fiber. The intranuclear organization of these proteins is dynamic and related to the metabolic state of the cell. Here we report that approximately 50% of the HMGN proteins are organized into macromolecular complexes in a fashion that is similar to that of other nuclear activities that modify the structure of the chromatin fiber. We identify several distinct HMGN-containing complexes that are relatively unstable and find that the inclusion of HMGN in the complexes varies according to the metabolic state of the cell. The nucleosome binding ability of HMGN in the complex is stronger than that of the free HMGN. We suggest that the inclusion of HMGN proteins into metastable multiprotein complexes serves to target the HMGN proteins to specific sites in chromatin and enhances their interaction with nucleosomes.

We describe an approach to quantum computer inspired by the information processing at the molecular level in living cells. It is based on the separation of a small ensemble of qubits inside the living system (e.g., a bacterial cell), such that coherent quantum states of this ensemble remain practically unchanged for a long time. We use the notion of a quantum kernel to describe such an ensemble. Quantum kernel is not strictly connected with certain particles; it permanently exchanges atoms and molecules with the environment, which makes quantum kernel a virtual notion. There are many reasons to expect that the state of quantum kernel of a living system can be treated as the stationary state of some Hamiltonian. While the quantum kernel is responsible for the stability of dynamics at the time scale of cellular life, at the longer inter-generation time scale it can change, varying smoothly in the course of biological evolution. To the first level of approximation, quantum kernel can be described in the framework of qubit modification of Jaynes-Cummings-Hubbard model, in which the relaxation corresponds to the exchange of matter between quantum kernel and the rest of the cell and is represented as Lindblad super-operators.

One of the key questions in the current molecular genetics of eukaryotes is how genetic information is retrieved from tightly packed chromatin. Acetylation of core histone N-termini is implicated in the regulation of chromatin function, and I summarize what is known about the mammalian enzymes that promote this posttranslational histone modification. Chromatin is important in gene expression not only because of the accessibility problem that it poses for the transcriptional machinery but also with regard to the phenomenon of chromatin memory, i.e. the ability of alternative chromatin states to be maintained through many cell divisions. This phenomenon is believed to be central to epigenetic inheritance [1], an important concept in developmental biology, which is also emerging as a contributing factor in cancer and other health disorders. Analyses of the composition of large multiprotein acetyltransferase complexes suggest their role in the mechanisms of epigenetic inheritance. The review will discuss some models pertinent to this function of histone acetyltransferases.

Histone acetyltransferases (HAT) play a critical role in transcriptional control by relieving repressive effects of chromatin, and yet how HATs themselves are regulated remains largely unknown. Here, it is shown that Twist directly binds two independent HAT domains of acetyltransferases, p300 and p300/CBP–associated factor (PCAF), and directly regulates their HAT activities. The N terminus of Twist is a primary domain interacting with both acetyltransferases, and the same domain is required for inhibition of p300-dependent transcription by Twist. Adenovirus E1A protein mimics the effects of Twist by inhibiting the HAT activities of p300 and PCAF. These findings establish a cogent argument for considering the HAT domains as a direct target for acetyltransferase regulation by both a cellular transcription factor and a viral oncoprotein.

We have isolated a human RNA polymerase II complex that contains chromatin structure remodeling activity and histone acetyltransferase activity. This complex contains the Srb proteins, the Swi-Snf complex, and the histone acetyltransferases CBP and PCAF in addition to RNA polymerase II. Notably, the general transcription factors are absent from this complex. The complex was purified by two different methods: conventional chromatography and affinity chromatography using antibodies directed against CDK8, the human homolog of the yeast Srb10 protein. Protein interaction studies demonstrate a direct interaction between RNA polymerase II and the histone acetyltransferases p300 and PCAF. Importantly, p300 interacts specifically with the nonphosphorylated, initiation-competent form of RNA polymerase II. In contrast, PCAF interacts with the elongation-competent, phosphorylated form of RNA polymerase II.

A unique aspect of the retrovirus life cycle is the obligatory integration of the provirus into host cell chromosomes. Unlike viruses that do not integrate, retroviruses must conserve an ability to activate transcription from a chromatin context. Human immunodeficiency virus (HIV)-1 encodes an unusual and an unusually potent transcriptional transactivator, Tat, which binds to a nascent viral leader RNA, TAR. The action of Tat has been well studied in various reductive model systems; however, the physiological mechanism through which Tat gains access to chromatin-associated proviral long terminal repeats (LTRs) is not understood. We show here that a nuclear histone acetyltransferase activity associates with Tat. Intracellularly, we found that Tat forms a ternary complex with p300 and P/CAF, two histone acetyltransferases (HATs). A murine cell defect in Tat transactivation of the HIV-1 LTR was linked to the reduced abundance of p300 and P/CAF. Thus, overexpression of p300 and P/CAF reconstituted Tat transactivation of the HIV-1 LTR in NIH3T3 cells to a level similar to that observed for human cells. By using transdominant p300 or P/CAF mutants that lack enzymatic activity, we delineated a requirement for the HAT component from the latter but not the former in Tat function. Finally, we observed that Tat-associated HAT is preferentially important for transactivation of integrated, but not unintegrated, HIV-1 LTR.

Satellite DNA, also known as tandemly repeated DNA, consists of clusters of repeated sequences and represents a diverse class of highly repetitive elements. Satellite DNA can be divided into several classes according to the size of an individual repeat: microsatellites, minisatellites, midisatellites, and macrosatellites. Originally considered as «junk» DNA, satellite DNA has more recently been reconsidered as having various functions. Moreover, due to the repetitive nature of the composing elements, their presence in the genome is associated with high frequency mutations, epigenetic changes and modifications in gene expression patterns, with a potential to lead to human disease. Therefore, the satellite DNA study will be beneficial for developing a treatment of satellite-related diseases, such as FSHD, neurological, developmental disorders and cancers. Сателітна ДНК, також відома як тандемно повторювана ДНК, складається з кластерів повторюваних послідовностей, об’єднаних у широкий клас часто повторюваних елементів. Сателітнi ДНК можна розділити на декілька класів залежно від розміру ок- ремого повтора: мікросателітні, мінісателітні, мідісателітні і макросателітні ДНК. Сателітну ДНК спочатку розглядали як «сміттєву». Лише зовсім недавно таку концепцію було переглянуто і наразі сателітну ДНК відносять до ДНК, якій притаманні різні функції. Крім того, присутність у геномі повторюваних послідовностей пов’язана з високою частотою мутацій, епігенетичними змінами і модифікаціями в профілі експресії генів, що потенційно може призвести до різних патологій. Таким чином, вивчення сателітної ДНК буде корисним при розробці терапії, спрямованої на лікування захворювань, пов’язаних iз сателітною ДНК, таких як м’язова дистрофія FSHD, неврологічні патології, хвороби, обумовлені порушеннями розвитку, та онкологічні захворювання. Сателлитная ДНК, также известная как тандемно повторяющаяся ДНК, состоит из кластеров повторяющихся последовательностей, объединенных в широкий класс часто повторяющихся элементов. Сателлитную ДНК можно разделить на несколько классов в зависимости от размера отдельного повтора: микросателлитная, минисателлитная, мидисателлитная и макросателлитная ДНК. Сателлитную ДНК первоначально рассматривали как «мусорную». Только совсем недавно эта концепция была пересмотрена, в результате чего сателлитную ДНК относят к ДНК, обладающей различными функциями. Кроме того, присутствие в геноме повторяющихся последовательностей связано с высокой частотой мутаций, эпигенетическими изменениями и модификациями в профиле экспрессии генов, что потенциально может привести к различным патологиям. Таким образом, изучение сателлитной ДНК будет полезно при разработке терапии, направленной на лечение заболеваний, таких как мышечная дистрофия FSHD, неврологические патологии, болезни, обусловленные нарушениями развития, и онкологические заболевания.

PCAF is a histone acetyltransferase that associates with p300/CBP and competes with E1A for access to them. While exogenous expression of PCAF potentiates both MyoD-directed transcription and myogenic differentiation, PCAF inactivation by anti-PCAF antibody microinjection prevents differentiation. MyoD interacts directly with both p300/CBP and PCAF, forming a multimeric protein complex on the promoter elements. Viral transforming factors that interfere with muscle differentiation disrupt this complex without affecting the MyoD–DNA interaction, indicating functional significance of the complex formation. Exogenous expression of PCAF or p300 promotes p21 expression and terminal cell-cycle arrest. Both of these activities are dependent on the histone acetyltransferase activity of PCAF, but not on that of p300. These results indicate that recruitment of histone acetyltransferase activity of PCAF by MyoD, through p300/CBP, is crucial for activation of the myogenic program.

Histone acetylation is thought to have a role in transcription. To gain insight into the role of histone acetylation in retinoid-dependent transcription, we studied the effects of trichostatin A (TSA), a specific inhibitor of histone deacetylase, on P19 embryonal carcinoma cells. We show that coaddition of TSA and retinoic acid (RA) markedly enhances neuronal differentiation in these cells, although TSA alone does not induce differentiation but causes extensive apoptosis. Consistent with the cooperative effect of TSA and RA, coaddition of the two agents synergistically enhanced transcription from stably integrated RA-responsive promoters. The transcriptional synergy by TSA and RA required the RA-responsive element and a functional retinoid X receptor (RXR)/retinoic acid receptor (RAR) heterodimer, both obligatory for RA-dependent transcription. Furthermore, TSA led to promoter activation by an RXR-selective ligand that was otherwise inactive in transcription. In addition, TSA enhanced transcription from a minimum basal promoter, independently of the RA-responsive element. Finally, we show that TSA alone or in combination with RA increases in vivo endonuclease sensitivity within the RA-responsive promoter, suggesting that TSA treatment might alter a local chromatin environment to enhance RXR/RAR heterodimer action. Thus, these results indicate that histone acetylation influences activity of the heterodimer, which is in line with the observed interaction between the RXR/RAR heterodimer and a histone acetylase presented elsewhere.

The p21(WAF1/CIP1/sdi1) gene product (WAF1) inhibits DNA replication in vitro (J. Chen, P. Jackson, M. Kirschner, and A. Dutta, Nature 374:386-388, 1995; S. Waga, G. Hannon, D. Beach, and B. Stillman, Nature 369:574-578, 1994), but in vivo studies on the antiproliferative activity of WAF1 have not resolved G1-phase arrest from potential inhibition of S-phase progression. Here, we demonstrate that elevated WAF1 expression can retard replicative DNA synthesis in vivo. The WAF1-mediated inhibitory effect could be antagonized by cyclin A, cyclin E, or the simian virus 40 small-t antigen with no decrease in the levels of WAF1 protein in transfected cells. Proliferating-cell nuclear antigen (PCNA) overexpression was neither necessary nor sufficient to antagonize WAF1 action. Expression of the N-terminal domain of WAF1, responsible for cyclin-dependent kinase (CDK) interaction, had the same effect as full-length WAF1, while the PCNA binding C terminus exhibited modest activity. We conclude that S-phase progression in mammalian cells is dependent on continuing cyclin and CDK activity and that WAF1 affects S phase primarily through cyclin- and CDK-dependent pathways.

In a recent publication, ‘A model of epigenetic evolution based on theory of open quantum systems’ (2013), the authors state: “We call our model quantum-like (QL) to distinguish it from really quantum models in cell biology: reducing cell’s behavior to quantum particles inside a cell, e.g., (Ogryzko 2008, 1997), McFadden and Al-Khalili (McFadden and Al-Khalili 1999), McFadden (McFadden 2000).”

p300/CBP is a transcriptional adaptor that integrates signals from many sequence-specific activators via direct interactions. Various cellular and viral factors target p300/CBP to modulate transcription and/or cell cycle progression. One such factor, the cellular p300/CBP associated factor (PCAF), possesses intrinsic histone acetyltransferase activity. Here, we demonstrate that p300/CBP is not only a transcriptional adaptor but also a histone acetyltransferase. p300/CBP represents a novel class of acetyltransferases in that it does not have the conserved motif found among various other acetyltransferases. p300/CBP acetylates all four core histones in nucleosomes. These observations suggest that p300/CBP acetylates nucleosomes in concert with PCAF.

Retinoids cause differentiation in embryonal carcinoma (EC) cells, thus mimicking events in mammalian development. Here, we show that retinoids also cause apoptosis in P19 EC cells. Characteristic DNA fragmentation was observed within 36 h after addition of retinoic acid (RA). Synthetic retinoids that are selective for RA receptors (RAR) were also effective in inducing apoptosis, whereas RXR selective ligands were without effect. The combination of RAR and RXR ligands resulted in a synergistic increase in apoptotic cell death. As with apoptosis, neuronal differentiation of P19 cells was synergistically induced by the combination of RAR and RXR ligands. Data obtained with an RAR antagonist and with P19 cells carrying a dominant negative RXR indicate that the two processes are receptor mediated. Together, our results indicate that retinoid-induced apoptosis and neuronal differentiation are closely coupled, and that both RAR and RXR play a role in these processes as active receptors for their respective ligands.

International audience; We have developed an approach termed PUB-NChIP (proximity utilizing biotinylation with native ChIP) to purify and study the protein composition of chromatin in proximity to a nuclear protein of interest. It is based on coexpression of (1) a protein of interest, fused with the bacterial biotin ligase BirA, together with (2) a histone fused to a biotin acceptor peptide (BAP), which is specifically biotinylated by BirA-fusion in the proximity of the protein of interest. Using the RAD18 protein as a model, we demonstrate that the RAD18-proximal chromatin is enriched in some H4 acetylated species. Moreover, the RAD18-proximal chromatin containing a replacement histone H2AZ has a different pattern of H4 acetylation. Finally, biotin pulse-chase experiments show that the H4 acetylation pattern starts to resemble the acetylation pattern of total H4 after the proximity of chromatin to RAD18 has been lost.