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Publié par | ludwig-maximilians-universitat_munchen |
Publié le | 01 janvier 2010 |
Nombre de lectures | 19 |
Poids de l'ouvrage | 13 Mo |
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STUDIES OF MECHANISMS CONTROLLING
DNA METHYLTRANSFERASE 1
CARINA FRAUER
MÜNCHEN 2010
STUDIES OF MECHANISMS CONTROLLING
DNA METHYLTRANSFERASE 1
CARINA FRAUER
Dissertation
an der Fakultät für Biologie
der Ludwig‐Maximilians‐Universität
München
vorgelegt von
Carina Frauer
aus Worms
München, den 14. Juni 2010
Erstgutachter: Prof. Dr. Heinrich Leonhardt
Zweitgutachter: Prof. Dr. Peter Becker
Tag der mündlichen Prüfung: 01.10.2010
CONTENT
CONTENT
Summary _________________________________________________________________________________________________ 1
1 Introduction _____________________________________________________________________________________ 3
1.1 DNA methylation in eukaryotes 3
1.1.1 Epigenetic gene regulation 3
1.1.2 Discovery of 5‐methylcytosine in DNA 4
1.1.3 Eukaryotic DNA methyltransferases 6
1.1.4 Distribution of 5‐methylcytosine in the mammalian genome 9
1.1.5 Regulation of gene expression by DNA methylation 14
1.1.6 DNA methylation dynamics 19
1.2 The Dnmt1 enzyme 23
1.2.1 Structure 23
1.2.2 Mechanism of the methyl transfer reaction 25
1.2.3 Substrate specificity 26
1.3 Regulation of Dnmt1 28
1.3.1 Transcriptional and translational Regulation 28
1.3.2 Regulation of Dnmt1 by post‐translational modifications 29
1.3.3 DNA binding and allosteric activation 29
1.3.4 Regulation by interaction with other factors 31
1.4 Aims of this work 33
2 Results ___________________________________________________________________________________________ 35
2.1 A versatile non‐radioactive assay for DNA methyltransferase activity and DNA binding 35
2.2 Modulation of protein properties in living cells using nanobodies 49
2.3 Different binding properties and functional relevance of CXXC zinc finger domains of enzymes
involved in cytosine modification 71
2.4 The multi‐domain protein Np95 connects DNA methylation and histone modification 101
2.5 Single molecule fluorescence spectroscopy of Dnmt1:DNA complexes 121
2.6 DNA methylation 133
I
CONTENT
3 Discussion _____________________________________________________________________________________ 135
3.1 Development of a versatile assay to measure DNA binding and methyltransferase activity 136
3.1.1 Potential of the developed assay 136
3.1.2 GBP binding enhances GFP fluorescence 138
3.1.3 Using the newly established tools for further applications 139
3.2 Maintenance methylation – a clear but demanding task 143
3.2.1 How Dnmt1 recognizes its substrate 143
3.2.2 The functional role of the Dnmt1 CXXC domain 145
3.2.3 The role of Uhrf1 in maintenance methylation and regulation of Dnmt1 148
3.2.4 Dnmt1:DNA complex stoichiometry 150
3.3 Outlook 152
3.3.1 Maintenance methylation ‐ more than a copy process? 152
3.3.2 On the role of Uhrf1 in maintenance methylation 153
3.3.3 The need for a three‐dimensional Dnmt1 structure 155
4 Annex __________________________________________________________________________________________ 157
4.1 References 157
4.2 Contributions 172
4.3 Declaration 174
4.4 Acknowledgements 175
5 Curriculum Vitae _____________________________________________________________________________ 177
II