TPP1 with ΔK170 mutation localizes to telomeres. (A) Western blot of WT or ΔK170 TPP1, overexpressed in 293T cells in the presence of siRNA against endogenous TPP1. Vector: empty plasmid transfection only. (B) Levels of endogenous TPP1 mRNA, measured by qRT-PCR using primers in the 5′ UTR of the ACD/TPP1 gene. 293T cells were transfected with plasmids encoding WT or ΔK170 TPP1, followed by transfection with siRNA targeting the 5′ UTR of ACD/TPP1 or control siRNA. Vector: empty plasmid transfection only. (C) Telomere ChIP of myc-tagged, siRNA-resistant TPP1, expressed in 293T cells in the presence of siRNA to reduce endogenous TPP1 levels. Shown are 5%, 10%, and 20% of the input chromatin used in each immunoprecipitation (top). Immunoprecipitation with an anti-myc antibody, in duplicate (bottom). Blot was probed for telomeric DNA. (D) Quantitation of the amount of telomeric DNA recovered as a percentage of input, in three independent transfections and ChIP experiments (data shown as mean ± standard error of the mean).