FEN1 and HIV-1 infection: Importantly, we found that productive HIV-1 infection is associated with an early activation of DNA replication components such as DNA polymerase subunits (POLA1, POLA2, POLD4 and POLE2), the origin replication complex protein ORC6L, the DNA primase PRIM1, the flap endonuclease FEN1, the DNA helicase and the DNA ligase LIG1 (Fig. 5, panel I).