Preparation of ACE2 293T cell line
ACE2 expressing human embryonic kidney cells (HEK293T) were generated by lentiviral transduction using pLENTI-hACE2-HygR (a gift from Raffaele De Francesco; Addgene plasmid#155296) (Notarbartolo et al., 2021). 72h after transduction the cells were FACS sorted based on the ACE2 expression detected with anti-hACE2 Alexa Fluor 488 conjugated antibodies (catalog #Fab9332G, clone#535919; R&D Systems). A CRE reporter was inserted into ACE2 293T cells using pLenti- V6.3 lox-dsRED-stop-lox-eGFP-blas (a gift from Ewa Snaar-Jagalska, Addgene plasmid #106171) (Heitzer et al., 2019). After selection with the Blasticidin, these cells were then FACS sorted based on their dsRED intensity.