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| Identifier |
uch.biology.phd//2003spilianakis |
| Title |
Μελέτη μηχανισμών μεταγραφικής ενεργοποίησης από το συνεργοποιητή MHC των τάξης ΙΙ γονιδίων, CIITA |
| Alternative Title |
Transcriptional vegulation of MHC class II genes from the class II transactivator, CIITA |
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Author
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Σπηλιανάκης, Χαράλαμπος Γ
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Thesis advisor
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Παπαματθαιάκης, Ι.
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| Abstract |
During my PhD studies I worked on the mechanisms regulating the expression of Major Histocompatibility Complex class II genes. MHC class II antigens are dimeric membrane glycoproteins that recognize and present antigenic peptides to T-lymphocytes. Their expression is highly regulated in transcriptional level and their stimulation needs the existence of an enhanceosome, which is composed on highly conserved sequences (HXY) of the proximal promoter, as well as the expression of CIITA, which is the major transcriptional regulator of the MHC class II genes. CIITA can positively regulate the expression of MHC class II genes upon its recruitment through its carboxy-terminal domain onto the class II enhanceosome and with its amino-terminal domain interacting with various other transcriptional coactivators. We showed that transcriptional coactivators such as CBP, pCAF and GCN5 interact physically with CIITA in vitro and in vivo and positively regulate the expression of class II antigens. CIITA not only interacts with these coactivators but it is being acetylated in discrete lysine residues that reside in an amino-terminal nuclear localization signal. Acetylation of CIITA results in increased nuclear accumulation of the protein and enhancement of transcriptional initiation. The subcellular localization of CIITA is also affected from its self-association. Self association of CIITA results in subcellular redistribution of the protein and its functional complementation. Its the first time, in the constraints of this study that the MHC class II enhanceosome was characterized using recombinant in vitro expressed proteins and not whole-cell extracts and it was shown the cooperative binding of all complexes onto the class II proximal promoter as well as the specificity in binding. We showed that the in vitro reconstituted enhanceosome can specifically recruit CIITA on the proximal promoter as well as other components of the basal transcription machinery. Using the technique of chromatin immunoprecipitation we showed the order of recruitment of all the factors needed for the induction of an MHC class II gene-DRA after the induction of cells with IFN-γ. It is an important result that a transcriptional transactivator such as CIITA can regulate the initiation and elongation of transcription regulating the levels of phosphorylation of specific serine residues of RNA polymerase II. This induction of DRA from IFN-γ is an inducible system of transcription that resembles the order of recruitment and induction of IFN-β gene upon virus induction, in that they both need an enhanceosome, preassembled for class II or inducible in IFN-β. Someone can take information concerning transcriptional regulation of genes in general, from the comparison of the two systems. It is more important trying to understand the transcription of class II genes and induction of expression in solid tumors where they are not normally expressed.
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| Language |
Greek |
| Subject |
Κύριο σύμπλοκο ιστοσυμβατότητας; Μεταγραφή; Συνενεργοποιητής τάξης ΙΙ; Σύνδρομο γυμνών λεμφοκυττάρων; Ανοσοκατακρήμνιση χρωματίνης; Πολυμεράση ΙΙ; Φωσφορυτίωση |
| Issue date |
2003-07-08 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Biology--Doctoral theses
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Type of Work--Doctoral theses
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| Views |
572 |
Μελέτη μηχανισμών μεταγραφικής ενεργοποίησης από το συνεργοποιητή MHC των τάξης ΙΙ γονιδίων, CIITA
