We demonstrated that MxB represses NUP358-mediated PIC nuclear import and HIV-1 replication. Moreover, MxB\'s effects on PIC nuclear import and HIV-1 replication depend critically on cofactor cleavage and polyadenylation specificity factor subunit 6 (CPSF6). MxB binds nucleoporin NUP358, blocks NUP358-CA interaction, thereby impeding the nuclear import of HIV-1 PIC with CPSF6 binding to PIC. More intriguingly, CPSF6\'s role in nuclear import depends on MxB, being a facilitator of HIV-1 nuclear import on its own, but becoming an inhibitor when MxB is present.
Our work establishes that MxB impedes the NUP358-mediated HIV-1 nuclear import and viral replication cooperatively with CPSF6.