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HIV-1 Gag Forms Ribonucleoprotein Complexes with Unspliced Viral RNA at Transcription Sites.
Kevin M Tuffy1, Rebecca J Kaddis Maldonado1, Jordan Chang1
1Division of Infectious Diseases and Epidemiology, Department of Medicine, Penn State College of Medicine, Hershey, PA 17033, USA.
Viruses
|November 13, 2020
Summary
Human immunodeficiency virus type 1 (HIV-1) Gag protein forms nuclear ribonucleoprotein complexes with unspliced viral RNA and Rev. This interaction occurs at viral transcriptional sites, facilitating HIV-1 replication.
Area of Science:
- Molecular Virology
- Cell Biology
- Retroviral Assembly
Background:
- Retroviral Gag proteins transiently traffic through the nucleus, a process implicated in genomic RNA packaging.
- While nuclear localization of Gag is observed in various retroviruses, its precise role, particularly in human immunodeficiency virus type 1 (HIV-1), remains unclear.
- HIV-1 Gag interacts with the Rev protein in nucleoli, which is crucial for genomic RNA export.
Purpose of the Study:
- To investigate the hypothesis that HIV-1 Gag interacts with Rev via viral RNA (vRNA) to form nuclear ribonucleoprotein (RNP) complexes.
- To determine the role of nuclear Gag-vRNA interactions in HIV-1 replication and assembly.
Main Methods:
- Utilized inducible HIV-1 proviral constructs in HeLa cells.
- Employed confocal microscopy for visualizing HIV-1 Gag and unspliced viral RNA (USvRNA) foci.
- Performed 2D co-localization studies and RNA-immunoprecipitation on fractionated cells.
- Analyzed 3D imaging and observed Gag localization in latently infected CD4+ T cells stimulated with prostratin.
Main Results:
- HIV-1 Gag and USvRNA were visualized in discrete nuclear foci, indicating specific interactions.
- Transcription inhibition increased Gag co-localization with USvRNA, suggesting accumulation on newly synthesized transcripts.
- HIV-1 Gag, USvRNA, and Rev formed a tripartite RNP complex in the perichromatin space.
- In CD4+ T cells, Gag localized to HIV-1 transcriptional burst sites, associating with USvRNA.
Conclusions:
- HIV-1 Gag binds to newly synthesized unspliced viral transcripts in the nucleus, forming viral RNPs.
- This nuclear RNP formation is a critical step in the HIV-1 life cycle, occurring at transcriptional sites.
- The findings elucidate a novel role for nuclear Gag trafficking in HIV-1 replication.
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