library_construction_protocol: Viable splenic hCD45+ cells from leukemic mice were sorted after continuous treatment with imetelstat or vehicle control. RNA was isolated from a maximum of 0.5 x 106 cells using the Qiagen RNeasy Micro kit according to the manufacturer's instructions. Replicates were taken from at least 2 different experiments. RNA samples were quantitated using the Nanodrop Spectrophotometer (Thermo Fischer Scientific) and the Qubit Fluorometer using the Qubit RNA HS Assay Kit (Molecular Probes) according to the manufacturer's recommendations. RNA integrity was confirmed using the RNA 6000 PICO Kit (Agilent Technologies) with analysis using the Agilent 2100 Bioanalyser (Agilent Technologies). Total RNA (100 _g) was used for NGS and prepared according to the NEBNext Ultra II RNA Library Prep Kit for Illumina (New England Biolabs, NEB; Cat# E7770S). Briefly, following mRNA isolation, fragmentation and priming, first and second strand cDNA were synthesised. The double-stranded cDNA was purified, A-tailed and ligated to adaptors. Following purification, the adaptor ligated DNA was enriched by PCR, purified and assessed for quality using the High Sensitivity DNA Kit (Agilent) on the Agilent 2100 Bioanalyser. Libraries were sequenced using a High output, single-end, 75 cycle (version 2) sequencing kit on the Illumina Nextseq 550 platform.