TERF2IP and breast carcinoma: The authors found that in breast cancer and osteosarcoma cell lines that maintain their telomere length through ALT, the telomere-associated protein SLX4IP promotes RAP1 SUMOylation by PIAS1, driving the detachment of RAP1 from telomeres and shuttling from the nucleus to the cytoplasm, which enhances its extratelomeric function.