Fig. 1

hTERT alternative splicing is regulated by a network of RNA-binding proteins. a TERT minigene reporter construct and products. CMV: human cytomegalovirus immediate-early enhancer and promoter, Bp: base pair, B6: variable nucleotide repeat in intron 6 from ref. ¹³, DR6 and DR8: direct repeat 6 or 8, respectively, from ref. ¹³, BGH polyA: signal bovine growth hormone polyadenylation signal. b hTERT steady-state isoform/splicing profile in non-small cell lung cancer cell lines (n = 3). c Differential expression analysis of splicing factors that correlated with high hTERT full-length expression in six non-small cell lung cancer cell lines. Log2 fold change in gene expression between the cell lines. CLK3 and SNRPB appear twice in the heatmap because two different microarray probes were differentially expressed between the high hTERT and low hTERT lines. d Differential expression analysis of splicing factors related to hTERT full-length expression, telomerase activity, and NOVA1 mRNA expression in the seven non-small cell lung cancer cell lines. Log2 fold change in gene expression between the cell lines. e Expression of NOVA1 protein and histone H3 protein in normal (HBECs) and cancerous lung cell lines. Representative western blot images are shown (n = 3). f Expression of NOVA1 mRNA by RT-ddPCR in a panel of human fetal and adult tissues. RT reverse transcription, ddPCR droplet digital PCR (n = 3). g siRNA knockdown of NOVA1 in H1299 and H920 lung cancer lines shifts hTERT splice isoform proportions as determined using RT-ddPCR (n = 6). h siRNA knockdown of NOVA1 in H1299 and H920 lung cancer lines reduces telomerase activity per cell equivalent (50 cell equivalents, n = 6, Student’s t test set at *p < 0.05 for significance). Data are expressed as means and standard error of the mean where applicable. Supplementary data associated with this figure can be found in Supplementary Figure 1