A hallmark of HIV type 1 and other lentiviruses is their ability to infect and replicate in nondividing cells by commandeering host nuclear transport factors. During the early stages of infection, this is expected to permit the safe passage of viral preintegration complexes (PICs) through nuclear pores. Numerous nuclear transport factors have been identified as essential for HIV-1 infection by genome-wide small interfering RNA screens, and many of these are currently under investigation. Here, using knockdown studies, Matreyek and Engelman further characterize the importance of transportin-3 and nuclear pore complex component nucleoporin 153 for the early stages of HIV-1 infection and show that these two proteins operate synergistically. Also, as was previously observed for transportin-3, they show that the requirement of nucleoporin 153 for PIC nuclear entry is determined by the HIV-1 Capsid protein. The refinement of the list of key nuclear pore complex and transport proteins required for PIC entry, along with a better understanding of the specific mechanisms employed, will undoubtedly lead to the development of future antiretroviral therapies that will have the potential to block HIV-1 viral DNA integration.