The transmembrane nucleoporin Nup210 weakens HIV-1 infection via modulating late events of viral nuclear import

OBJECTIVE: Nuclear import/export of HIV-1 is regulated by the nuclear pore complexes (NPCs), but the impact of many individual nucleoporins on viral infection is unclear. Here, we investigated the role of a transmembrane nucleoporin Nup210 in HIV-1 infection. DESIGN/METHODS: TZM-bl cells with Nup210-knockdown or overexpression were infected with either wildtype HIV-1 NL4-3 or VSV-G pseudotyped NL4-3-KFS. The efficiency of viral infection was assessed by measuring luciferase activity. The DNA levels of reverse transcription, nuclear entry, and proviral DNA integration were determined by qPCR. The levels of unspliced, singly spliced, and fully spliced mRNA were determined by RT-qPCR. The levels of viral key proteins were determined by western blotting. The viral DNA, mRNA, and protein assays were also performed in Raltegravir-treated Nup210-knockdown or overexpression cells. RESULTS: Generally, Nup210-knockdown promoted HIV-1 infection, whereas Nup210-overexpression had no significant effect on entire infection. Several findings were obtained in further investigations. First, Nup210-knockdown increased the accumulation of integrated proviral DNA, while the levels of reverse transcription (RT) products and 2-LTR circles remained unaffected by either Nup210-knockdown or overexpression. Second, Nup210 regulated viral mRNA alternative splicing, particularly, Nup210-knockdown resulted in the highest increase in singly spliced Vpr mRNA, whereas Nup210-overexpression led to the biggest rise in unspliced Gag mRNA. Third, Vpr expression was elevated by Nup210-knockdown, suggesting that Vpr may act as a viral antagonist of Nup210. Additionally, Raltegravir, together with Nup210, inhibit viral infection by interfering proviral DNA integration, subsequent transcription and translation. CONCLUSION: The endogenous Nup210 is sufficient to suppress HIV-1 infection by downregulating late steps of viral nuclear entry.