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. Author manuscript; available in PMC: 2012 Jun 1.
Published in final edited form as: Nat Struct Mol Biol. 2011 Nov 20;18(12):1371–1375. doi: 10.1038/nsmb.2174

Figure 1.

Figure 1

The RNA accordion model for primer positioning and translocation. (a) Secondary structure of T. thermophila TER, with the inset showing the sequence of the template, the TBE and the TRE. The template is boxed; the alignment region is white and the sequence that is reverse transcribed is yellow; (b) Accordion model for template progression and translocation of telomerase. Left, in wild-type (WT) TER, primer extension is accompanied by compaction of the TRE and extension of the TBE. Right, deletion of nucleotides in the TRE (delta symbol) prevents bound primer 1 from reaching the active site, giving No reaction. Primer 2, which pairs near the 5′ end of the template, is able to undergo one round of extension. The active site of TERT is represented as a grey circle. Distances d and d′ represent our assumption that the position of the active site remains constant relative to an anchored TRE and TBE, respectively. The template sequence is represented as boxes, colored as in panel a. Primers are in black, newly added nucleotides in red. A maximum of seven base pairs forms between the primer and template30,31.