ATR and Fanconi anemia: We assessed the importance of several reported targets for ALT cancer cells: FANCM (a protein of the Fanconi Anemia pathway that suppresses telomeric replication stress in ALT cells),10,13,14,19,25,26 HIRA (a modulator of histone H3.3 deposition contributing to recombination activities at ALT telomeres),5 and ATR (a regulator of recombination at ALT telomeres).4