We found that after IFN-α pretreatment and wild-type HIV-1 infection, 2-LTR circles were reduced in parental THP-1 cells ∼30-fold, and only ~10-fold in MX2g2-4 cells, corroborating the role for MX2 in blocking nuclear import (Fig. 4D). Here, IFNA1 is linked to HIV-1 infection.