Human telomeric RNA r(UAGGGU) sequence forms parallel tetraplex structure with U-quartet.

Recent studies showed that telomere DNAs are transcribed into telomeric-repeat-containing RNAs in mammalian cells and these RNAs are associated with the chromosome ends. Therefore, they may be key components of telomere machinery. We have reported that the human telomeric RNA sequence forms parallel G-quadruplex structure in the presence of Na(+) ions. In the current study, using a combination of CD and NMR experiments, we found that the human telomeric RNA r(UAGGGU) sequence can form parallel tetraplex structure with U-quartet in the presence of K(+) or Na(+) ions. These results provide valuable information to allow understanding of the molecular basis of human telomeric RNA structure.