Telomeres and Their Biology
In contrast to prokaryotic chromosomes and plasmids, which are usually circular, most eukaryotic chromosomes are composed of linear DNA. The organisation of genomes into linear chromosomes poses two major challenges for chromosome metabolism. First, conve
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Telomeres and Their Biology Maria F. Siomos and Karel Riha
Contents
5.1
5.1
A Historical Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
5.2 5.2.1 5.2.2 5.2.3 5.2.4 5.2.5
Telomere Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Telomeric DNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Secondary Structure of Telomeric DNA . . . . . . . . . . . . . . . . . . . Telomere Binding Proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DNA Repair Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Telomeric Chromatin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
72 72 73 74 76 77
5.3 5.3.1 5.3.2 5.3.3 5.3.4
Telomere Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The End Replication Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Telomerase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Telomere Replication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Telomerase Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
77 77 78 78 79
5.4
Telomere Dysfunction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
K. Riha (*) Austrian Academy of Sciences, Gregor Mendel Institute of Molecular Plant Biology, Dr. Bohr-Gasse 3, 1030 Vienna, Austria e-mail: [email protected] J.F. Wendel et al. (eds.), Plant Genome Diversity Volume 1, DOI 10.1007/978-3-7091-1130-7_5, # Springer-Verlag Wien 2012
A Historical Perspective
In contrast to prokaryotic chromosomes and plasmids, which are usually circular, most eukaryotic chromosomes are composed of linear DNA. The organisation of genomes into linear chromosomes poses two major challenges for chromosome metabolism. First, conventional DNA replication processes are unable to completely replicate the 30 ends of linear chromosomes (known as the ‘end replication problem’) and second, the natural ends of linear chromosomes must be distinguished from DNA double-strand breaks. This is necessary so that they are protected from being recognised as DNA damage and being inappropriately repaired by, for example, the formation of chromosome fusions. To overcome these problems, eukaryotes have evolved specialised nucleoprotein complexes at the ends of linear chromosomes called telomeres. Telomeres have their own replication mechanism and serve as a protective chromosome end capping structure. The notion that chromosome ends have special properties that set them apart from other chromosomal regions stems from experiments undertaken by Hermann J. M€uller and Barbara McClintock in the 1920s and 1930s. When observing chromosomes of the fruit fly Dros
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