Conserved Tertiary Structure of hTR: pseudoknot essential for function
Telomeres are the physical ends of eukaryotic chromosomes and are comprised of a DNA repeat sequence (TTAGGG). Telomeric DNA consists of thousands of copies of this G-rich repeat at the 3’ terminal end of the chromosome. (Theimer et al., 2005). Over successive rounds of DNA replication, the chromosome ends fail to get fully replicated and so are slowly degraded over time. Telomeres capping these ends protect the genetic information in the chromosomes because only non-coding telomeric DNA is lost through rounds of replication. This ensures that the entire DNA sequence is replicated without loss of genetic information due to chromosomal degradation or rearrangement.
Nucleotides 93-184 comprise this pseudoknot region. Stem 1 is highlighted in red
Stem 2 is highlighted in blue.
Loop 1 is highlighted in yellow.
This uridine rich loop lies in the major groove of stem 2
. Loop 2 is highlighted in green.
This adenine-rich loop lies in the minor groove of stem 1.
The Hoogsteen base pair
at the stem/loop junction positions the stems such that the major and minor grooves are
contiguous along the entire length of the structure.
The Hoogsteen base pair (A173-U99) at the stem/loop junction positions the stems such that the major and minor grooves are contiguous along the entire length of the structure.