Sebastian Glatt

Bio: Sebastian Glatt is an academic researcher from Jagiellonian University. The author has contributed to research in topics: TRNA modification & Transfer RNA. The author has an hindex of 20, co-authored 39 publications receiving 1066 citations. Previous affiliations of Sebastian Glatt include Boehringer Ingelheim & European Bioinformatics Institute.

Molecular structures of unbound and transcribing RNA polymerase III

Abstract: Transcription of genes encoding small structured RNAs such as transfer RNAs, spliceosomal U6 small nuclear RNA and ribosomal 5S RNA is carried out by RNA polymerase III (Pol III), the largest yet structurally least characterized eukaryotic RNA polymerase. Here we present the cryo-electron microscopy structures of the Saccharomyces cerevisiae Pol III elongating complex at 3.9 A resolution and the apo Pol III enzyme in two different conformations at 4.6 and 4.7 A resolution, respectively, which allow the building of a 17-subunit atomic model of Pol III. The reconstructions reveal the precise orientation of the C82-C34-C31 heterotrimer in close proximity to the stalk. The C53-C37 heterodimer positions residues involved in transcription termination close to the non-template DNA strand. In the apo Pol III structures, the stalk adopts different orientations coupled with closed and open conformations of the clamp. Our results provide novel insights into Pol III-specific transcription and the adaptation of Pol III towards its small transcriptional targets.

The Elongator subcomplex Elp456 is a hexameric RecA-like ATPase

Abstract: Elongator was initially described as an RNA polymerase II-associated factor but has since been associated with a broad range of cellular activities. It has also attracted clinical attention because of its role in certain neurodegenerative diseases. Here we describe the crystal structure of the Saccharomyces cerevisiae subcomplex of Elongator proteins 4, 5 and 6 (Elp456). The subunits each show almost identical RecA folds that form a heterohexameric ring-like structure resembling hexameric RecA-like ATPases. This structural finding is supported by different complementary in vitro and in vivo approaches, including the specific binding of the hexameric Elp456 subcomplex to tRNAs in a manner regulated by ATP. Our results support a role of Elongator in tRNA modification, explain the importance of each of the Elp4, Elp5 and Elp6 subunits for complex integrity and suggest a model for the overall architecture of the holo-Elongator complex.

Architecture of the yeast Elongator complex.

Abstract: The highly conserved eukaryotic Elongator complex performs specific chemical modifications on wobble base uridines of tRNAs, which are essential for proteome stability and homeostasis. The complex is formed by six individual subunits (Elp1-6) that are all equally important for its tRNA modification activity. However, its overall architecture and the detailed reaction mechanism remain elusive. Here, we report the structures of the fully assembled yeast Elongator and the Elp123 sub-complex solved by an integrative structure determination approach showing that two copies of the Elp1, Elp2, and Elp3 subunits form a two-lobed scaffold, which binds Elp456 asymmetrically. Our topological models are consistent with previous studies on individual subunits and further validated by complementary biochemical analyses. Our study provides a structural framework on how the tRNA modification activity is carried out by Elongator.

Cardiac fibrosis in myocardial infarction—from repair and remodeling to regeneration

Abstract: Ischemic cell death during a myocardial infarction leads to a multiphase reparative response in which the damaged tissue is replaced with a fibrotic scar produced by fibroblasts and myofibroblasts. This also induces geometrical, biomechanical, and biochemical changes in the uninjured ventricular wall eliciting a reactive remodeling process that includes interstitial and perivascular fibrosis. Although the initial reparative fibrosis is crucial for preventing rupture of the ventricular wall, an exaggerated fibrotic response and reactive fibrosis outside the injured area are detrimental as they lead to progressive impairment of cardiac function and eventually to heart failure. In this review, we summarize current knowledge of the mechanisms of both reparative and reactive cardiac fibrosis in response to myocardial infarction, discuss the potential of inducing cardiac regeneration through direct reprogramming of fibroblasts and myofibroblasts into cardiomyocytes, and review the currently available and potential future therapeutic strategies to inhibit cardiac fibrosis. Graphical abstract Reparative response following a myocardial infarction. Hypoxia-induced cardiomyocyte death leads to the activation of myofibroblasts and a reparative fibrotic response in the injured area. Right top In adult mammals, the fibrotic scar formed at the infarcted area is permanent and promotes reactive fibrosis in the uninjured myocardium. Right bottom In teleost fish and newts and in embryonic and neonatal mammals, the initial formation of a fibrotic scar is followed by regeneration of the cardiac muscle tissue. Induction of post-infarction cardiac regeneration in adult mammals is currently the target of intensive research and drug discovery attempts.

Dynamic regulation of transcriptional states by chromatin and transcription factors

Abstract: The interaction of regulatory proteins with the complex nucleoprotein structures that are found in mammalian cells involves chromatin reorganization at multiple levels. Mechanisms that support these transitions are complex on many timescales, which range from milliseconds to minutes or hours. In this Review, we discuss emerging concepts regarding the function of regulatory elements in living cells. We also explore the involvement of these dynamic and stochastic processes in the evolution of fluctuating transcriptional activity states that are now commonly reported in eukaryotic systems.