SAFB and cancer: By using specific RT-qPCR primers targeting the aforementioned L1HS-Ta at Chr22-q12.1 (Fig. 2e), the most active RC-L1 in human cancers,22 we examined its expression upon depleting SAFB, METTL3 and YTHDC1 in MCF7 cells where this L1HS-Ta is active.68 This experiment revealed reduction of this single live L1 (Fig. 4e), in a manner similar to pan-L1HS (the entirety of all L1HS in the genome) or other dead L1s.