TERF1 and carcinoma: Furthermore, co-immunofluorescence staining of γH2AX foci with RAP1, another shelterin component localized at telomeres, showed increased number of DNA damage foci at telomeres in Trf1Δ/ΔK-Ras+/G12Vp53−/− than in Trf1+/+K-Ras+/G12Vp53−/− carcinomas (Fig3B).