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PSF acts through the human immunodeficiency virus type 1 mRNA instability elements to regulate virus expression

Andrei S Zolotukhin1, Daniel Michalowski, Jenifer Bear

  • 1Human Retrovirus Pathogenesis Section, Basic Research Laboratory, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, MD 21702-1201, USA.

Molecular and Cellular Biology
|August 29, 2003
PubMed

Insights

The HIV-1 Rev protein counteracts regulatory elements (INS) that hinder viral mRNA. We found that p54nrb/PSF binds INS RNA, inhibiting viral gene expression and revealing a novel regulatory pathway.

Area of Science:

  • Molecular Biology
  • Virology
  • Gene Regulation

Background:

  • Human immunodeficiency virus type 1 (HIV) utilizes cis-acting regulatory elements (INS) within gag/pol and env mRNAs.
  • These INS elements impair mRNA stability, nucleocytoplasmic transport, and translation through poorly understood mechanisms.
  • The viral Rev protein effectively counteracts this downregulation, promoting efficient mRNA export and expression.

Purpose of the Study:

  • To elucidate the molecular mechanism by which INS elements regulate HIV-1 mRNA.
  • To identify cellular factors that interact with INS elements and mediate their function.
  • To understand how the viral Rev protein overcomes INS-mediated repression.

Main Methods:

  • In vitro RNA binding assays to assess p54nrb/PSF interaction with INS RNA.
  • In vivo co-immunoprecipitation to detect p54nrb association with INS-containing mRNA.
  • Analysis of authentic HIV-1 mRNAs from infectious molecular clones to study PSF effects on viral transcripts.

Main Results:

  • The INS region of HIV-1 gag mRNA was identified as a high-affinity ligand for the heterodimeric transcription/splicing factor p54nrb/PSF.
  • Both p54nrb and PSF subunits demonstrated similar affinity and specificity for INS RNA in vitro.
  • In vivo, INS-containing subgenomic gag mRNA specifically associated with p54nrb, and PSF inhibited its expression via the INS element.
  • PSF was found to specifically affect INS-containing, Rev-dependent transcripts encoding Gag-Pol and Env from authentic HIV-1 mRNAs.
  • p54nrb exhibited continuous nuclear export and cytoplasmic association with INS-containing mRNA, suggesting a role in later mRNA metabolism stages.

Conclusions:

  • p54nrb/PSF acts as a key mediator of INS element function in HIV-1 mRNA regulation.
  • The interaction between p54nrb/PSF and INS RNA defines a novel mRNA regulatory pathway exploited by HIV-1.
  • This pathway involves both nuclear and cytoplasmic functions of p54nrb, impacting mRNA stability, transport, and translation.

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