Extended Data Fig. 2: Characterization of TERC-null 293T cells.

a, Schematic of TERC genotypes in TERC-null 293T cells generated by genome-editing, including a deletion of the essential box H domain on one allele, and an 821-bp TERC locus deletion that encompasses 74 bp from the 3’ end of TERC on the other allele. b, Ethidium bromide stained agarose gel of PCR of 293T or 293T TERC-null genomic DNA using primers flanking the deletions indicated in a. c, Sanger sequencing of gel-purified PCR products from the (1) higher molecular weight bands in b, indicating that the non-deleted allele lacks the box H domain, and (2) the ∆821 bp deleted band from b, with trace file showing the deletion junction in a genomic context. d, RT-qPCR of TERC expression relative to GAPDH in wild-type 293T and TERC-null 293T cells, performed in technical triplicate. P value calculated by unpaired t test. Data are shown are means and error bars indicate standard deviation. e, Telomerase activity measured via the TRAP assay, performed on 5-fold serial dilutions of lysates. HI indicates heat-inactivated lysate. IC indicates the internal control product. f, TRF of wild-type and TERC-null 293T cells. Days of culture were recorded beginning approximately two months after gene editing. Telomere length gradually declines with passage until cells universally senesce. g, Quantification of f, line fit using simple linear regression. Data presented in this figure are the results of single experiments unless otherwise indicated.