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Human immunodeficiency virus type 1 Vpr-binding protein VprBP, a WD40 protein associated with the DDB1-CUL4 E3

Chad M McCall1, Paula L Miliani de Marval, Paul D Chastain

  • 1Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA.

Molecular and Cellular Biology
|July 9, 2008
PubMed

Insights

VprBP is crucial for DNA replication and cell cycle progression. Its disruption leads to S-phase defects, embryonic lethality, and suggests HIV-1 Vpr may hijack this process for viral replication.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Virology

Background:

  • Damaged DNA binding protein 1 (DDB1) forms E3 ligase complexes with WD40 repeat proteins (DWDs).
  • Vpr-binding protein (VprBP) is a DWD protein implicated in HIV-1 Vpr-induced G2 cell cycle arrest, but its cellular function is unknown.

Purpose of the Study:

  • To characterize the cellular function of VprBP.
  • To investigate the role of VprBP in DNA replication and cell cycle progression.
  • To explore the potential link between VprBP function and HIV-1 replication.

Main Methods:

  • Co-immunoprecipitation assays to determine protein interactions.
  • Western blotting to analyze protein levels during the cell cycle.
  • Chromatin immunoprecipitation to assess DNA binding.
  • siRNA-mediated silencing and gene deletion in cell lines and mouse models.
  • Flow cytometry to analyze cell cycle progression.

Main Results:

  • VprBP interacts with DDB1, CUL4A, and other components of the COP9/signalsome.
  • VprBP levels fluctuate during the cell cycle, decreasing during mitosis.
  • VprBP binds to chromatin in a cell cycle-dependent manner, peaking in G2.
  • VprBP depletion impairs DNA replication, causes S-phase arrest, inhibits proliferation, and leads to embryonic lethality in mice.
  • Conditional deletion in mouse embryonic fibroblasts results in S-phase defects and apoptosis.

Conclusions:

  • VprBP plays a critical, previously unrecognized role in S-phase progression and DNA replication.
  • HIV-1 Vpr may exploit VprBP's function in chromosomal replication to enhance viral replication.
  • VprBP is essential for embryonic development and cell proliferation.

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