FIGURE 1.

Diagram of TER secondary structures highlighting functional motifs. The template, pseudoknot, TBE, and STE are common to ciliate, yeast, and vertebrate TERs. The STE is distal stem–loop IV in T. thermophila, conserved region 4/5 (CR4/5) in human, and a three-way helix junction in yeasts. Species-specific RNP stability elements recruit p65 in T. thermophila, H/ACA proteins in human, and Sm proteins in yeasts (also Ku in Saccharomyces). The binding sites for holoenzyme proteins that do not affect RNA stability, namely Est1 in yeasts and the CAB box-binding protein WDR79/TCAB1 in humans, are indicated. T. thermophila TER also contains a template recognition element (TRE) that contributes to template utilization.