Heinz, Kathrin (2018)
Effect of heterochromatin (com)position on DNA replication timing.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung
Kurzbeschreibung (Abstract)
The accurate replication of the genome prior to each cell division is of upmost importance as mistakes are potentially transferred to subsequent generations but can also lead to genetic mutations, karyotype aberrations or to diseases that may result in cancer or cell death. Therefore, the duplication of the genome is one of the most crucial processes in any living organism and thus essential for development and reproduction.\\ The process of DNA replication is a highly organized process, both spatially and temporally, where specific genomic regions undergo DNA replication at distinct times during S-phase (Synthesis-phase). During development of an organism, DNA replication is a flexible process and several chromatin properties have been proposed as potential regulators thereof. Although a lot is known on the composition of the basic DNA replication machinery, it is mostly unclear, how its activity is regulated.\\ In the context of the present thesis, I made use of different targeting and manipulation approaches to elucidate the impact of potential regulators that control DNA replication dynamics in mammalian cells. To this end, I established and validated a novel targeting strategy to manipulate and reposition subcellular structures and molecules.\\ I first took advantage of constitutive heterochromatin as a prominent and well-characterized structure within the mammalian nucleus and repositioned it to the nuclear lamina to assess the nuclear position of DNA as one potential regulator of DNA replication dynamics. Using time-lapse microscopy, I was able to observe that constitutive heterochromatin, known to replicate during late S-phase, was replicated during mid S-phase when repositioned to the nuclear periphery. For this reason, I proposed that constitutive heterochromatin was activated in \textit{trans} according to the domino model of origin activation by nearby (mid S) firing origins. This data provided a novel approach to reposition large genomic regions and to manipulate nuclear DNA position within the nucleus. Here, I established the nuclear position as a novel regulator of DNA replication timing.\\ Secondly, I made use of female \textit{Microtus cabrerae} cells, which are characterized by their very prominent giant sex chromosomes with large coupled heterochromatic blocks. Again, I made use of a well-defined structure within the nucleus and manipulated the histone acetylation level as another potential regulator of DNA replication timing. First, I manipulated the global acetylation level by HDAC inhibition via drug-treatment and secondly, I specifically targeted a histone acetyltransferase to the inactive and active X chromosome. I elucidated the impact of histone acetylation level on DNA replication dynamics in the vole genome. I was able to show that both manipulation assays, global and site-directed, were sufficient to significantly increase the histone acetylation level, resulting in a prolongation of total S-phase duration and substage duration. The DNA replication onset of facultative heterochromatin was shifted toward early S-phase, as DNA content was further increased in early S-phase in treated samples. I was able to detect a negative effect of histone hyperacetylation on DNA replication fork speed. Here, I assessed the validity and reproducibility of DNA replication regulation by histone acetylation level across species.
Typ des Eintrags: | Dissertation | ||||
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Erschienen: | 2018 | ||||
Autor(en): | Heinz, Kathrin | ||||
Art des Eintrags: | Erstveröffentlichung | ||||
Titel: | Effect of heterochromatin (com)position on DNA replication timing | ||||
Sprache: | Englisch | ||||
Referenten: | Cardoso, Prof. Dr. M. Cristina ; Laube, Prof. Dr. Bodo | ||||
Publikationsjahr: | 2018 | ||||
Ort: | Darmstadt | ||||
Datum der mündlichen Prüfung: | 26 Oktober 2018 | ||||
URL / URN: | https://tuprints.ulb.tu-darmstadt.de/8168 | ||||
Zugehörige Links: | |||||
Kurzbeschreibung (Abstract): | The accurate replication of the genome prior to each cell division is of upmost importance as mistakes are potentially transferred to subsequent generations but can also lead to genetic mutations, karyotype aberrations or to diseases that may result in cancer or cell death. Therefore, the duplication of the genome is one of the most crucial processes in any living organism and thus essential for development and reproduction.\\ The process of DNA replication is a highly organized process, both spatially and temporally, where specific genomic regions undergo DNA replication at distinct times during S-phase (Synthesis-phase). During development of an organism, DNA replication is a flexible process and several chromatin properties have been proposed as potential regulators thereof. Although a lot is known on the composition of the basic DNA replication machinery, it is mostly unclear, how its activity is regulated.\\ In the context of the present thesis, I made use of different targeting and manipulation approaches to elucidate the impact of potential regulators that control DNA replication dynamics in mammalian cells. To this end, I established and validated a novel targeting strategy to manipulate and reposition subcellular structures and molecules.\\ I first took advantage of constitutive heterochromatin as a prominent and well-characterized structure within the mammalian nucleus and repositioned it to the nuclear lamina to assess the nuclear position of DNA as one potential regulator of DNA replication dynamics. Using time-lapse microscopy, I was able to observe that constitutive heterochromatin, known to replicate during late S-phase, was replicated during mid S-phase when repositioned to the nuclear periphery. For this reason, I proposed that constitutive heterochromatin was activated in \textit{trans} according to the domino model of origin activation by nearby (mid S) firing origins. This data provided a novel approach to reposition large genomic regions and to manipulate nuclear DNA position within the nucleus. Here, I established the nuclear position as a novel regulator of DNA replication timing.\\ Secondly, I made use of female \textit{Microtus cabrerae} cells, which are characterized by their very prominent giant sex chromosomes with large coupled heterochromatic blocks. Again, I made use of a well-defined structure within the nucleus and manipulated the histone acetylation level as another potential regulator of DNA replication timing. First, I manipulated the global acetylation level by HDAC inhibition via drug-treatment and secondly, I specifically targeted a histone acetyltransferase to the inactive and active X chromosome. I elucidated the impact of histone acetylation level on DNA replication dynamics in the vole genome. I was able to show that both manipulation assays, global and site-directed, were sufficient to significantly increase the histone acetylation level, resulting in a prolongation of total S-phase duration and substage duration. The DNA replication onset of facultative heterochromatin was shifted toward early S-phase, as DNA content was further increased in early S-phase in treated samples. I was able to detect a negative effect of histone hyperacetylation on DNA replication fork speed. Here, I assessed the validity and reproducibility of DNA replication regulation by histone acetylation level across species. |
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Alternatives oder übersetztes Abstract: |
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URN: | urn:nbn:de:tuda-tuprints-81688 | ||||
Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 500 Naturwissenschaften und Mathematik > 570 Biowissenschaften, Biologie | ||||
Fachbereich(e)/-gebiet(e): | 10 Fachbereich Biologie 10 Fachbereich Biologie > Cell Biology and Epigenetics |
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Hinterlegungsdatum: | 18 Nov 2018 20:55 | ||||
Letzte Änderung: | 18 Nov 2018 20:55 | ||||
PPN: | |||||
Referenten: | Cardoso, Prof. Dr. M. Cristina ; Laube, Prof. Dr. Bodo | ||||
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: | 26 Oktober 2018 | ||||
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