FIG. 2.

At template position ⁴⁷⁰C, the reverse transcription can be continued (upper right) or aborted (bottom). With the ⁴⁶⁹A→U mutant telomerase, the different possibilities can be distinguished based on the incorporated telomere sequence (indicated below the TLC1 template sequence; newly incorporated nucleotides are highlighted). For reasons of simplicity, all 5′-TGGGTGTGGGT-3′ sequences were attributed to alignment at position ⁴⁷⁶C (bottom left). However, product dissociation at position ⁴⁷³C followed by realignment with ⁴⁷⁹C would also result in the incorporation of the same telomeric sequence. Therefore, the number given on the bottom left is probably an overestimate of the alignment frequency at ⁴⁷⁶C. The number of events indicated for alignment 3′ of position ⁴⁷⁹C (bottom right) comprises both position ⁴⁸³C and position ⁴⁸¹C. Only the latter is represented in the scheme. Repeats not listed in the figure resulted from product dissociation 3′ of position ⁴⁷⁰C.