Figure 1. A distal block of repeats in intron 6 is necessary for TERT alternative splicing.

(a) Splicing of TERT pre-mRNA (not to scale) without the block of repeats in intron 6 results in exclusively full-length splicing, where all exons are included in the final transcript. (b) Splicing of TERT pre-mRNA in the presence of the block of repeats in intron 6 produces both the full-length transcript and an alternatively splice transcript called minus beta as a result of the skipping of exons 7 and 8. The minus beta splice form is non-functional because exons 7 and 8 are in the reverse transcriptase domain and required for telomerase activity.