Unique C. elegans telomeric overhang structures reveal the evolutionarily conserved properties of telomeric DNA.
Bottom Line: There are two basic mechanisms that are associated with the maintenance of the telomere length, which endows cancer cells with unlimited proliferative potential.We show that the telomeric DNA from C. elegans and humans forms fundamentally different secondary structures.The unique structural characteristics of C. elegans telomeric DNA that are distinct not only from those of humans but also from those of other multicellular eukaryotes allowed us to identify evolutionarily conserved properties of telomeric DNA.
Affiliation: Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Kralovopolska, 135, 612 65 Brno, Czech Republic.Show MeSH
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Mentions: Previous studies using short constructs based on four repeats of human telomeric DNA have demonstrated that both C- and G-rich strands can adopt intramolecular tetraplex structures (47). As shown by others for extended human telomeric G-rich sequences (53–56) (Figure 3A and B) and as demonstrated by our CD and NMR spectra (Figure 1), this property is preserved even for extended constructs of C-rich human telomeric DNA. In addition to vertebrate telomeric DNA, the simultaneous formation of tetraplex structures in both C- and G-rich strands was observed for telomeric DNA from evolutionarily distal eukaryotic species, such as plants, insects, or unicellular eukaryotes (22,57). However, whereas the C. elegans (nematode) G-rich telomeric DNA was previously shown to preferentially fold into a G-quadruplex structure (57), we find that the C-rich strand of the telomeric C. elegans DNA adopts duplex-based motif. While these observations on one hand support idea of the G-quadruplex in the G-rich strand as an evolutionarily conserved property of telomeric DNA, they argue against evolutionary conservation of the i-motif in the C-rich strand of telomeric DNA.
Affiliation: Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Kralovopolska, 135, 612 65 Brno, Czech Republic.