Beitrag der Histonacetylierung zur Signalintegration auf dem C 4-spezifischen Phosphoenolpyruvat-carboxylase Gen in Mais (Zea mays L.)

The expression of the C4-specific phosphoenolpyruvate carboxylase gene (C4-Pepc) in maize (Zea mays L.) is regulated by multiple internal and external stimuli. C4-Pepc gene expression is restricted to mesophyll cells within foliar leaves but its activity is further induced by light and modulated by the availability of nutrients and sugars. The aim of this thesis was to analyse the impact of histone acetylation on the integration of these signals on the C4-Pepc promoter. Three out of five tested lysine residues showed a high level of background acetylation in roots and coleoptiles although the C4-Pepc gene is constitutively repressed in these tissues. A similar acetylation pattern was observed in etiolated foliar leaves, where the gene is also inactive but can be activated by illumination. The difference between the constitutively inactive state and the inducible state is therefore not based on a different acetylation pattern but rather on the existence of a leaf-specific histone acetyltransferase (HAT) / histone deacetylase (HDAC) system. Upon illumination, specifically histone H4 lysine 5 and histone H3 lysine 9 on the promoter and the transcribed region were acetylated. These modifications were independent of transcriptional activity of the C4-Pepc gene and were furthermore completely reversed in the dark. In contrast to illumination, acetylation of all the lysines analysed was modulated by nutrient and sugar availability but this effect was limited to a distal promoter element. Here, the level of acetylation correlated linearly with the transcriptional activity of the C4-Pepc gene. Together with experiments in illuminated but transcriptionally inactive bundle sheaths it was shown that the light stimulus is necessary and sufficient to induce histone acetylation on the proximal promoter element. Inhibition of HDACs in etiolated foliar leaves was shown to be insufficient for transcriptional activation of the C4-Pepc promoter. Further studies with such inhibitors revealed that spatial distribution of histone acetylation on the gene region was regulated by either HAT or HDAC activity depending on the specific lysine tested. The light induced increase in histone acetylation was caused by reduced HDAC activity. In contrast, metabolic regulation of the distal promoter acetylation at least for histone H3K9 was brought about by modulation of HAT activity. Analysis of acetylation dynamics revealed a high turnover of acetyl groups on the distal promoter whereas on the proximal promoter reduced dynamics of acetylation were observed. Based on these findings a model was proposed with three independent control elements that collectively regulate the C4-Pepc promoter activity. The results argue for a simple charge neutralization model on the distal promoter and a more complex and stimulus dependent acetylation pattern on the proximal promoter that is independent of transcriptional activity of the C4-Pepc gene and that might be part of a more complex histone code.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2008

Author dc:creator

• Offermann, Sascha

Contributors dc:contributor

• Peterhänsel, Christoph

• info:eu-repo/classification/ddc/570
• Chromatin
• Transkription <Genetik>
• Histone
• Acetylierung
• Nucleosom
• Mais
• Phosphoenolpyruvatcarboxylase
• Histon-Acetyltransferase
• Biowissenschaften, Biologie
• ChIP
• Chromatinimmunopräzipitation
• Histonmodifikation
• Signalintegration
• Chromatinimmunoprecipitation
• histone code
• signal integration

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-112512%22

OAI record oai:identifier

https://publications.rwth-aachen.de/oai2d?verb=GetRecord&metadataPrefix=oai_dc&identifier=oai%3Apublications.rwth-aachen.de%3A49944