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| Identifier |
uch.biology.phd//2001syntichaki |
| Title |
Μηχανισμός αναδιαμόρφωσης της χρωματίνης μέσω της ακετυλίωσης των ιστονών |
| Alternative Title |
Mechanism of chromatin remodeling through the histone acetylation |
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Author
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Συντυχάκη, Καλλιόπη
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| Abstract |
The Gcn5 histone acetyltransferase (HAT) is part of a large multimeric complex (SAGA) that is required for transcriptional activation in yeast. This complex can acetylate in vitro and in a Gcn5-dependent manner both nucleosomal and core free histones. One major question is whether the HAT activity of Gcn5 is necessary and sufficient for its in vivo function as transcriptional coactivator. In the first part of this study, mutated Gcn5 proteins with severely attenuated in vitro HAT activities were generated. Despite their apparent loss in enzymatic activity, these GCN5 derivatives complemented all the defects of a gcn5 strain. This was due to the potentiation of their HAT activity when assembled into native complexes, as revealed by measuring the activities of the mutated proteins produced in yeast cells in the presence or absence of another SAGA component, Ada2. This potentiation was best elaborated on polynucleosomal substrates, which are the physiological substrates for the complex. Kinetic enzymatic analyses showed that the assembly of Gcn5 derivatives within their native complexes enhanced the rate of catalysis suggesting a regulatory role for other subunits of SAGA. In the second part of the study a synthetic promoter was generated with known nucleosomal organization and dependent of the function of Gcn5. The existence of positioned nucleosomes allowed the in vivo studies of chromatin remodeling. It was revealed that transcription driven by this promoter required the coordinated function of both SAGA and the ATP-dependent chromatin remodeling complex SWI/SNF. Both complexes were recruited independently by the Gcn4 activator but histone acetylation by SAGA did not require the function of SWI/SNF. Yet, acetylation per se was not sufficient for nucleosome remodeling and transcriptional activation. Remodeling was accomplished by the function of SWI/SNF on acetylated substrates, in a manner independent of transcription. Finally, it was shown that the functional coordination of SAGA and SWI/SNF was mediated from the function of bromodomains of the Gcn5 and Swi2/Snf2.
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| Language |
Greek |
| Subject |
Ιστόνες; Ακετυλίωση; Μηχανισμός αναδιαμόρφωσης; Χρωματίνη; Σύμπλοκα; Μεταγραφική ενεργοποίηση |
| Issue date |
2001-04-26 |
| 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 |
2791 |
Μηχανισμός αναδιαμόρφωσης της χρωματίνης μέσω της ακετυλίωσης των ιστονών
