To apply the KI approach to a functional analysis in the context of HIV-1 infection in resting CD4+ T cells, we introduced the eGFP gene upstream of the SAMHD1 locus to generate a GFP-SAMHD1 fusion protein (Fig. 5a), which is a Vpx-degradable (Extended Data Fig. 9) and enzymatically active analog of non-tagged SAMHD1. Here, PSME3 is linked to HIV-1 infection.