Maturation of human telomerase RNA component from an extended precursor

Here, we develop nascent RNAend-Seq, in which we isolate nascent RNA and sequence the 3' ends of RNA precursors. Using a pulse-chase experimental design, we follow extended precursors of the telomerase RNA component (hTR) and show that the mature telomerase RNA derives from these species with slow kinetics compared to other small non-coding RNAs. The human disease causing gene PARN further delays maturation of the hTR precursor in PARN- mutant cancer cell lines. Disruption of the poly(A)polymerase PAPD5 in PARN-mutant cells restores normal processing kinetics and levels of mature hTR. Unexpectedly, neither PARN nor PAPD5 is required for hTR processing. Instead, PAPD5 and PARN set the hTR maturation rate by controlling precursor adenylation. Overall design: Examination of hTR 3' ends in HeLa and hES cells and in nascent RNA. For all nascent RNA experiments, two replicates performed per time point.