Fig. 5: Reducing the expression level of LARP3 increases telomerase function and causes telomere elongation.

a Western blots of cell extracts prepared from K562 cells treated with shRNAs targeting luciferase or LARP3. Endogenous tubulin served as a loading control. b Total RNA from LARP3 knockdown K562 cells was subjected to qRT‒PCR to measure the levels of total hTR, 3′-extended hTR, GAPDH, ATP5β, and HPRT. Bar graph of the mean fold change for 3′-extended hTR relative to that of the control samples normalized to GAPDH, ATP5β, and HPRT. The mean values +/− SEM were calculated from triplicate qRT‒PCR experiments of three biological replicates. Dots represent data points from individual experiments. The significance of changes between samples was calculated with a two-sided Student’s t test; *p < 0.05, **p < 0.01, ***p < 0.005, ****p < 0.001. c An in vitro 3′ end processing assay with ³²P-labelled hTR fragments was carried out in the indicated cell extracts. RNA was resolved on a 6% polyacrylamide gel containing 8 M urea. Actin served as the loading control. The mean values +/− SD were calculated from triplicate experiments of three technical replicates. Dots represent data points from individual experiments. The significance was calculated with a two-sided Student’s t test; *p < 0.05, **p < 0.01, ***p < 0.005, ****p < 0.001. d Western blotting analysis of telomerase assembled on biotin-labelled hTR in the indicated extracts, followed by pulldown with streptavidin beads for the indicated times. e Endogenous DKC1 was immunoprecipitated and subjected to a telomerase activity assay. f Bar graph of the mean fold change in telomerase activity relative to the control group. The mean values +/− SEM were calculated from three biological replicates with a two-sided Student’s t test. g Telomere lengths determined by TRF analysis of gDNA prepared from K562 cells treated with shRNAs targeting luciferase or LARP3. Source data are provided as a Source data file.