BLM and Bloom syndrome: Mammalian TRF1 specifically mitigates lagging strand replication stress by promoting the recruitment of BLM (Bloom syndrome) (Martinez et al., 2009; Sfeir et al., 2009; Zimmermann et al., 2014), a RecQ family helicase which is capable of unwinding G4s which would impede replisome progression (Drosopoulos et al., 2015; Sun et al., 1998).