Maria Contreras - Academia.edu (original) (raw)
Uploads
Papers by Maria Contreras
Nature Reviews Genetics, 2005
The ends of chromosomes are formed by telomeres -special chromatin structures that are essential ... more The ends of chromosomes are formed by telomeres -special chromatin structures that are essential to protect these regions from recombination and degradation activities 1 . In vertebrates, telomeres are composed of tandem repeats of the TTAGGG sequence that are bound by specific proteins 1 . They are also the substrate for telomerase, a DNA polymerase that can elongate them in those cell types in which it is expressed 2,3 . Interestingly, telomeres continuously lose TTAGGG repeats in a way that is coupled to cell division, owing to the incomplete replication of linear chromosomes by conventional DNA polymerases -the so-called 'end-replication problem' . This progressive telomere shortening is proposed to represent a 'molecular clock' that underlies organismal ageing 2,3 . In particular, telomere shortening to a critical length results in loss of telomere protection, which leads to chromosomal instability and loss of cell viability. As an exception, germ cells and some cancer cells express high levels of telomerase, which prevents critical telomere shortening and maintains cell viability 3 .
Nature Reviews Genetics, 2005
The ends of chromosomes are formed by telomeres -special chromatin structures that are essential ... more The ends of chromosomes are formed by telomeres -special chromatin structures that are essential to protect these regions from recombination and degradation activities 1 . In vertebrates, telomeres are composed of tandem repeats of the TTAGGG sequence that are bound by specific proteins 1 . They are also the substrate for telomerase, a DNA polymerase that can elongate them in those cell types in which it is expressed 2,3 . Interestingly, telomeres continuously lose TTAGGG repeats in a way that is coupled to cell division, owing to the incomplete replication of linear chromosomes by conventional DNA polymerases -the so-called 'end-replication problem' . This progressive telomere shortening is proposed to represent a 'molecular clock' that underlies organismal ageing 2,3 . In particular, telomere shortening to a critical length results in loss of telomere protection, which leads to chromosomal instability and loss of cell viability. As an exception, germ cells and some cancer cells express high levels of telomerase, which prevents critical telomere shortening and maintains cell viability 3 .