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RNA polymerase: The "meeting point" of regulatory networks
Wiedermannová, Jana ; Krásný, Libor (advisor) ; Pospíšek, Martin (referee) ; Valášek, Leoš (referee)
Bacterial RNA polymerase (RNAP) is a multisubunit complex essential for transcription of DNA into RNA. As a key enzyme responsible for regulation of gene expression it interprets regulatory signals from the cell and based on these cues RNAP adjusts transcription level of particular genes. This process is affected both by the regular subunits of RNAP as well as other transcription factors (TFs) directly or indirectly interacting with RNAP. The general focus of this Thesis was to extend the knowledge about the complex transcriptional regulatory networks and about the connections between individual pathways. The main specific topic and the main publication of the thesis are focused on the HelD protein, a novel binding partner of RNAP in Bacillus subtilis. We showed that HelD binds between the secondary channel of RNAP and alpha subunits of the core form of the enzyme. We proved that HelD stimulates transcription in an ATP dependent manner by enhancing transcriptional cycling and elongation. We revealed a new connection in the transcription regulatory machinery when we demonstrated that the stimulatory effect of HelD can be amplified by delta, a small subunit of RNAP specific for gram positive (G+) bacteria. Two other publications of the thesis are dealing with the delta subunit. We solved the 3D...
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Regulation of transcription in mycobacteria.
Páleníková, Petra ; Krásný, Libor (advisor) ; Mrvová, Silvia (referee)
The bacterial cell has to be able to cope with environmental changes. Adaptation to these changes is achieved by changes in gene expression. Gene expression is regulated mostly at the level or transcription initiation. Transcription initiation depends on the sequence of promoters and is regulated by alternative sigma factors and many transcription factors acting either as activators or repressors. This work describes various ways of transcription regulation in the bacterial genus Mycobacterium that includes deathly pathogens such as M. tuberculosis and M. leprae. The typical characteristics of this genus are poorly conserved promoters, a high number of sigma and transcription factors, the presence of two-component systems and a lot of small RNAs that have not been characterized in detail so far.
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Factors interacting with bacterial RNA polymerase
Sudzinová, Petra ; Krásný, Libor (advisor) ; Fišer, Radovan (referee)
The bacterial cell must be able to rapidly change its gene expression to survive unstable external conditions. Transcription is the key level that affects gene expression. The pivotal enzyme of transcription is RNA polymerase (RNAP). Activity of RNAP is tightly regulated by transcription factors (TFs). These factors affect RNAP in different ways. This work presents an overview of various proteins and others factors, description of their effects on transcription and also mechanisms of their actions. TFs could be divided according to various criteria. In this work, TFs are divided according to how they interact with RNAP: TFs interacting only with RNAP; TFs binding simultaneously DNA and RNAP; TFs interacting with RNA and RNAP. This work presents a comprehensive overview of various TFs that are involved in the bacterial cell's reprogramming of gene expression that is required to withstand the changes in the environment.
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Factors affecting gene expression in Bacillus subtilis
Sudzinová, Petra ; Krásný, Libor (advisor) ; Vopálenský, Václav (referee) ; Vohradský, Jiří (referee)
Bacterial DNA-dependent RNA polymerase (RNAP) is a key enzyme of bacterial transcription. Its activity must be tightly regulated. This could be done on the level of promoter DNA topology recognition, by changing the intracellular levels of metabolites, or by binding proteins, known as transcription factors. Even though the RNAP regulatory network has been intensively studied for decades, new regulators are still being described. The main focus of this Thesis is to characterize some of them: i) HelD, a novel RNAP interacting factor, with so far unknown protein 3D structure; ii) RNase J1, an enzyme with a unique mechanism of functioning; iii) Spx, a major regulator of gene expression in Bacillus subtilis, with still new roles to be defined and iv) the effect of the topological state of promoters on transcription. We identified HelD as an interacting protein of RNAP in Bacillus subtilis and described its biochemical properties. It stimulates transcription in an ATP-dependent manner, by enhancing recycling of RNAP molecules (Publication I). We published the first insight into the HelD structure by SAXS (small angle X-ray scattering) and deepened the understanding of HelD domain composition (Publication III). And finally, we were able to solve the cryo-EM structure of HelD:RNAP complexes from...
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Function of sigma factors in strains of genus Rhodococcus
Nový, David ; Štěpánek, Václav (advisor) ; Sudzinová, Petra (referee)
Thanks to their large genome sizes, rhodococci share considerable biotechnological potential, however, there is still little known about the regulation of gene expression during the initiation of transcription process. The knowledge of this process might help to optimize biotechnological application. A large number of sigma factors are involved in the transcriptional regulation of rhodococci and this number often positively correlates with their genome sizes. Sigma factors can be potentially divided into two groups: the first, conserved factors that may in some variants occur in many different species among bacteria, and the second, specific sigma factors, that have been evolutionarily selected in individual strains due to environmental and lifestyle conditions. All sigma factors present in rhodococci belong to the σ70 family and can also be divided into four groups according to the presence of conserved structural domains (groups 1 to 4). A special type of sigma factors with extracytoplasmic function (ECF, group 4) are factors carrying specific domains at their C-terminus, namely NTF- 2-like or TPR, whose functions are still not fully understood. Very little information about the physiological functions of individual sigma factors in rhodococci has been published but it can be supplemented by...
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SigN from Bacillus subtilis: Functional characterization.
Kambová, Milada ; Krásný, Libor (advisor) ; Nešvera, Jan (referee)
Bacillus subtilis strain 3610 is an ancestral undomesticated strain. It diers from the laboratory strain 168 in many aspects. One dierence in strain 3610 is the presence of plasmid pBS32 encoding the sigma factor N (σN). This σ factor is activated when DNA damage occurs and induces the bacteria's cell death. The aim of the Thesis was a systematic characterisation of σN-dependent transcription. First, I showed that plasmid-borne but not chromosome-borne predicted σN-dependent promoters were ac- tive in transcription in vitro. Next, the anities of RNAP with σN for DNA, initiating NTP (iNTP) were determined for both relaxed and supercoiled DNA templates. Sur- prisingly, the activity of RNAP on relaxed σN-dependent promoters was higher than on their supercoiled versions, an opposite trend than displayed by RNAP associated with other σ factors. This property of σN-dependent promoters was not encoded by the core promoter sequence. In summary, this Thesis contributed to our understanding of the bacterial transcription apparatus. 1
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Factors interacting with bacterial RNA polymerase and their effect on the regulation of transcription initiation
Ramaniuk, Volha
(ENGLISH) The bacterial cell needs to regulate its gene expression in response to changing environmental conditions. RNA polymerase (RNAP) is the pivotal enzyme of this process and its activity is controlled by a number of auxiliary factors. Here I focus on RNAP-associating factors involved in regulation of transcription in G+ bacteria: factors, initiating nucleoside triphosphates (iNTPs), HelD, δ and small RNA Ms1. The main emphasis is on σ factors from Bacillus subtilis. σ factors allow RNAP to specifically recognize promoter DNA. In my first project I set up in vitro transcription systems with purified alternative σ factors, σB , σD , σH , σI from B. subtilis. Using these systems, I studied the effect of initiating NTP concentration ([iNTP]) on transcription initiation. I showed that promoters of alternative factors are often regulated by [iNTP]. In the next project I comprehensively characterized one of the least explored alternative factors from B. subtilis, I . I identified ~130 genes affected by I , though only 16 of them were directly affected. Moreover, I discovered that I is involved in iron metabolism. Finally, I showed that I binding requires not only the conserved -35 and -10 hexamers, but also extended -35 and -10 elements located in the spacer region. In collaboration with...
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Overlaps of sigma factors regulons of RNA polymerase in Corynebacterium glutamicum
Zíková, Jaroslava ; Pátek, Miroslav (advisor) ; Sudzinová, Petra (referee)
Sigma factor (σ) is a part of the RNA polymerase enzyme complex. This complex (referred to as a holoenzyme) ensures the recognition of the consensus promoter sequences of the individual genes and the initiation of transcription. Seven sigma factors were found in Corynebacterium glutamicum. The genome of this bacterium encodes one primary factor σA and another six alternative sigma factors: σB , σC , σD , σE , σH a σM . These alternative sigma factors are expressed in response to changes in the internal and external environment and ensure the adaption of the bacterium to growth conditions. They are also one of many ways to regulate gene expression at the transcriptional level. In specific cases, the regulation of gene expression is caused by alternative sigma factors that recognize corresponding dual (recognized alternatively by two sigma factors) or overlapping promoters. Thus, the genes controlled by these promoters are classified into overlapping regulons. Key words: Corynebacterium glutamicum, sigma factor, RNA polymerase, transcription, promoter, regulons, RNA-seq, in vitro transcription, in vivo two-plasmid system
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Factors affecting gene expression in Bacillus subtilis
Sudzinová, Petra ; Krásný, Libor (advisor) ; Vopálenský, Václav (referee) ; Vohradský, Jiří (referee)
Bacterial DNA-dependent RNA polymerase (RNAP) is a key enzyme of bacterial transcription. Its activity must be tightly regulated. This could be done on the level of promoter DNA topology recognition, by changing the intracellular levels of metabolites, or by binding proteins, known as transcription factors. Even though the RNAP regulatory network has been intensively studied for decades, new regulators are still being described. The main focus of this Thesis is to characterize some of them: i) HelD, a novel RNAP interacting factor, with so far unknown protein 3D structure; ii) RNase J1, an enzyme with a unique mechanism of functioning; iii) Spx, a major regulator of gene expression in Bacillus subtilis, with still new roles to be defined and iv) the effect of the topological state of promoters on transcription. We identified HelD as an interacting protein of RNAP in Bacillus subtilis and described its biochemical properties. It stimulates transcription in an ATP-dependent manner, by enhancing recycling of RNAP molecules (Publication I). We published the first insight into the HelD structure by SAXS (small angle X-ray scattering) and deepened the understanding of HelD domain composition (Publication III). And finally, we were able to solve the cryo-EM structure of HelD:RNAP complexes from...
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Intracellular and intercellular regulation of gene expression in Gram-positive bacteria.
Pospíšil, Jiří ; Krásný, Libor (advisor) ; Lichá, Irena (referee) ; Malínský, Jan (referee)
Bacteria, the most dominant organisms on Earth, are an everyday presence in our lives. Symbiotic bacteria, which are present in the digestive tract of animals, usually have a beneficial effect on the body. On the opposite side of the spectrum are pathogenic species that cause more or less serious diseases around the world. In order to fight pathogens effectively, it is necessary to learn as much as possible about the molecular mechanisms by which bacteria respond to their environment, and also about the types of communication within bacterial populations that allow them to react to environmental changes as "multicellular" organisms. This Thesis consists of two main parts. In the first part, selected aspects of bacterial gene expression are characterized, using Bacillus subtilis and Mycobacterium smegmatis as model organisms. DNA-dependent RNA polymerase (RNAP) is the enzyme that is responsible for transcription of DNA into RNA, and thus plays a key role in gene expression. This Thesis deals with the structure of bacterial RNAP and important auxiliary factors (proteins and RNA) that associate with this enzyme and modulate its function. In the second part, the focus is on cell-to-cell communication, revealing which factors/mechanisms, including gene expression, affect this process in B. subtilis....
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