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Función del gen dRYBP en "Drosophila melanogaster"

Autor González González, María Inmaculada
DirectorBusturia, Ana
Palabras clave Genes homeóticos
Fecha de publicación 2007
EditorUniversidad Autónoma de Madrid
ResumenThe Polycomb (PcG) and trithorax (trxG) groups of genes are involved in the mechanisms of maintenance of gene expression during development. The PcG genes are required for the maintenance of the repressed transcriptional state and the trxG genes are needed for the maintenance of the active transcriptional state. They were initially discovered in Drosophila as regulators of homeotic gene expression. However, it is now known that they are conserved from worms to mammals and that they regulate at least 100 genes of the fly genome. In order to understand the mechanism of action of the PcG/trxG proteins, it is necessary to know the factors therein involved. The aim of this Thesis work has been to study the role of the dRYBP ( Ring and YY1 Binding Protein) gene in the mechanisms of maintenance of gene expression mediated by the PcG/ trxG proteins. The conclusions of this work are the following: 1) There is only one dRYBP gene in Drosophila, philogenetically conserved, and coding for only one protein with a Zn Finger domain. 2) The expression of the dRYBP protein is ubiquitous and nuclear throughout development. The nuclear pattern of expression localizes with the “Polycomb bodies”. The pattern of expression during mitosis is dynamic, i.e dRYBP is associated to chromatin during anafase and dissociated of the chromatin at metafase. 3) Lack of function of dRYBP generates phenotypes with variable penetrance and expressitivity including a) lethality throughout development, b) developmental delay, c) defects in mitosis progression, d) production of melanizations in the larval tissue, e) decrease in the imaginal discs size, f) lack of apposition of the ventral and dorsal wing surfaces, and g) sterility 4) The GALDB-dRYBP protein behaves as a transcriptional repressor throughout development. This repression is dependent on PcG proteins 5) dRYBP interacts genetically with the Sex comb extra (PcG), and the trithorax (trxG) genes. Moreover, dRYBP protein interacts molecularly with SCE and PHO, both of the PcG. 6) Over expression of dRYBP generates: a) homeotic phenotypes dependent of PcG and trxG, and b) lack of transcriptional silencing mediated by the MCP138 of the homeotic Abdominal-B gene. 7) The mechanism involved in the generation of the homeotic phenotypes could be due to the “sequestration” of the PcG and trxG proteins mediated by dRYBP. If so, the dRYBP protein is able to recruit the PcG and the trxG protein complexes. Moreover, this recruitment is mediated by the C-terminal domain of the dRYBP protein. 8) Over expression of dRYBP activates apoptosis exclusively in the haltere and the wing imaginal discs. This activation requires the apoptotic factors and the dFADD and DREDD proteins. Also, the activation of the apoptosis seem to require the N terminal domain of the dRYBP protein 9) The dRYBP induced apoptosis is modulated by high levels of the TRX protein. Moreover, high levels of the TRX protein, but not of the PC and SCE proteins, activate apoptosis. 10) The dRYBP gene has properties of both the Polycomb and the trithorax genes, and therefore, can be included in the group of ETP (Enhancer of Trithorax and Polycomb) genes.
Descripción Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología Molecular. Fecha de lectura 23-03-2007
URI http://hdl.handle.net/10261/8342
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