SMAD2 and infection: To address whether A83-mediated reprogramming enhancement is attributed to the unexpected increase of p-SMAD2/3, we performed reprogramming after knocking out both Smad2 and Smad3 in dox-inducible MKOS MEFs with constitutive Cas9 expression by infection of lentiviral guide RNA (gRNA) expression vectors (Figure S3D) (Tzelepis et al., 2016).