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Role of methyltransferases in fungal development and secondary metabolite productionSarikaya Bayram, Özlem 17 January 2014 (has links)
Pilzentwicklung und Sekundärmetabolismus werden durch Einwirkung von
Umwelteinflüssen von Regulatorproteinen kontrolliert. Das VeA Protein repräsentiert die
velvet-Domänen-Familie der Pilzregulatoren. VeA passt die sexuelle Entwicklung und den
dazu gehörenden Sekundärmetabolismus von Aspergillus nidulans an die Lichtverhältnisse
an. VeA bindet im Dunkeln an VelB und bildet schließlich den trimeren VelB-VeA-LaeA
(velvet) Komplex. VeA dient als Brückenprotein für das velvet-Domänen-Protein VelB als
Regulator der Entwicklung und die Methyltransferase LaeA als Regulator des
Sekundärmetabolismus. VelB kann mit VosA einen zweiten licht-regulierten Komplex
bilden, der die asexuelle Entwicklung reprimiert. Auch VosA gehört zur Familie der Velvet-
Proteine. LaeA kontrolliert die Bildung der VelB-VosA und VelB-VeA-LaeA Komplexe
während der Entwicklung. laeA Nullmutationen können nicht mehr auf Licht reagieren, was
ihre Schlüsselrolle als Regulatoren der Entwicklung unterstreicht. Die Abwesenheit von LaeA
führt zur Bildung von wesentlich kleineren Fruchtkörpern. Grund hierfür ist das Fehlen
runder Hülle-Zellen, die den jungen Fruchtkörper ernähren und in seiner Entwicklung
unterstützen. LaeA spielt damit eine dynamische Rolle während der morphologischen und
biochemischen Entwicklung des Pilzes, indem die Expression, Interaktion und die
Modifikation der velvet Regulatoren kontrolliert werden. Im zweiten Teil der Arbeit wurde
die VeA-Plattform für Protein-Protein Interaktionen weiter untersucht. VeA interagierende
Proteine (Vips) identifiziert in einen „Yeast-two-hybrid“ System führten zu einem trimeren
Methyltransferase-Komplex, der Signaltransduktion mit epigenetischer Kontrolle verbindet.
Der neuartige Komplex enthält das Plasmamembran-assoziierte Trimer VapA-VipC-VapB.
Das Dimer VipC-VapB ist über das FYVE-ähnliche Zinkfinger Protein VapA an die
Plasmamembran gebunden und ermöglicht dem nuklearen VelB-VeA-LaeA Komplex die
Aktivierung der Transkription der sexuellen Entwicklung. Sobald die Abkopplung vom VapA
stattgefunden hat, wird VipC-VapB zum Kern transportiert. VipC-VapB interagiert
physikalisch mit VeA, vermindert dessen Transport zum Kern und die Stabilität. Folglich
wird der Anteil des VelB-VeA-LaeA Komplexes im Kern reduziert. Die nukleare VapB
Methyltransferase vermindert die Entstehung des fakultativen Chromatins indem es die
Histon 3 Lysin 9 Methylierung (H3K9 me3) vermindert. Dies begünstigt die Aktivierung der
frühen Regulatorgene flbA und flbC, die dann das asexuelle Programm im Licht vorantreiben.
Der VapA-VipC-VapB Methyltransferase-Weg vereinigt die Kontrolle des Kernimportes und
der Stabilität von Transkriptionsfaktoren mit der Modifikation von Histonen. Erst dieses
komplexe Zusammenspiel unterschiedlicher Mechanismen erlaubt eine angemessene Antwort
für die Differenzierung des Pilzes.
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Meaning in Small, Snyders and Pearce : an application of Lotman’s semiotics to ‘coloured’ literatureErnest, David Solomon Harold 17 October 2005 (has links)
In this study, a semiotic point of view of selected literature written by ‘coloured’ writers is examined, using some of the semiotic theories of Jurij M. Lotman, one of the leading Soviet semioticians of the school of Tartu. Selected theories of Lotman are applied to ‘coloured’ literature. These include an examination of poetic language (based on Lotman’s theory of a primary and secondary modelling system), the iconicity of the text, the aesthetics of identity and opposition, the distinction between text and extra-text, and the relationship that exists between the extra-text, culture and code. The literary texts chosen for analysis are works by three contemporary ‘coloured’ writers, namely Adam Small, Peter Snyders and Robert Pearce, who have all contributed poetry, prose and drama to Afrikaans literature in general, and original Afrikaans literature in particular. The selected dramas are Joanie Galant-hulle (Small 1978), Political Joke (Snyders 1983) and Die Laaste Supper in Marabastad (Pearce 1988b)*. These writers’ works span approximately three consecutive decades and their work can be examined for commonality and differences. The three chosen dramas were written five years apart respectively; yet they reveal thematic similarities. The dramas also feature a common ‘deviant’ language code used by ‘coloured’ people and discussed in this study as original Afrikaans. This code, which is juxtaposed with standard Afrikaans, is one of the basic areas of interest that motivated the choice of subject for this study. The primary objective of this study is to examine the differentiation that Lotman makes between the various sign systems that operate in natural language (the primary modelling system) and poetic language (a secondary modelling system), and to determine whether these sign systems can be detected and are functional in ‘coloured’ literature. In addition, an investigation is made of the iconicity that operates in poetic language (which, according to Lotman, is the basis for differentiation), and to ascertain whether iconicity occurs in these examples of ‘coloured’ literature and to what extent it influences meaning. In the process, intratextual relations within the poetic text were scrutinised to establish whether the manipulation of language, devices and codes raises any particular expectation in the poetic text, and also to detect whether oppositionally constituted code-systems which set up their own patterns of expectation within the syntactic and lexical levels of the poetic text clash with and contradict prior expectations. In addition, an analysis has been made to determine whether a new understanding of the texts can be reached, based on Lotman’s aesthetics of identity and opposition, and to what extent the reader is forced to collaborate in the modelling process of the texts when the reader’s expectations are undermined by an aesthetics of opposition. The study has successfully corroborated and substantiated all the selected aspects of Lotman’s theory. The differentiation that Lotman makes between the primary and secondary language model is demonstrated especially by the iconicity that operates in poetic language. Examples are abundant in the selected literature and are conspicuous, especially through the manipulation of the language, devices and codes employed by the authors to defamiliarise objects so that they transcend their familiar characteristics and perceptions, and sometimes signify a totally new concept. In this way, readers’ expectations are subverted and they are invited to collaborate in the modelling process of the texts. These techniques are also an integral part of both the text and the extra-text, and their presence justifies Lotman’s claims that the meaning of a literary text cannot be understood outside its cultural or historical context. In retrospect, it can be argued that this research has opened up some additional avenues for an analysis of meaning in ‘coloured’ literature. / Dissertation (MA (English))--University of Pretoria, 2004. / English / unrestricted
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