Interaction of HIV-1 Tat with purα in nuclei of human glial cells: Characterization of RNA-mediated protein-protein binding

Margaret J. Wortman, Chavdar P. Krachmarov, Julie H. Kim, Ronald G. Gordon, Lara G. Chepenik, John N. Brady, Gary L. Gallia, Kamel Khalili, Edward M. Johnson

Research output: Contribution to journalArticlepeer-review

Abstract

A complex between the Tat protein, encoded by human immunodeficiency virus type 1 (HIV-1), and the cellular protein, Purα, has been implicated in activation of the late promoter of JC virus (JCV) and in enhancement of JCV DNA replication. JCV is the causative agent of progressive multifocal leukoencephalopathy (PML), an acquired immunodeficiency syndrome (AIDS) opportunistic infection of the brain. Purα also binds the HIV-1 TAR RNA element and activates HIV-1 transcription, suggesting a role for RNA binding in the action of this protein. Using immunoelectron microscopy, we find that in human glial cells expressing both proteins, Tat and Purα are colocalized in extranucleolar chromatin structural elements. The colocalized Purα and Tat are nearly exclusively nuclear, although individual proteins can be seen in both nucleus and cytoplasm, suggesting a preferential tropism of the complex for the nucleus. Analysis of the interaction between purified proteins indicates that the Tat-Purα interaction is strongly enhanced by the presence of RNA. Tat amino acids from 37-48 are essential for Tat binding. Residues 49-72, including the TAR RNA-binding domain, are critical for binding to Purα, while Cys22, in the Tat transactivation domain, is responsible for an important global effect. Purα repeat II domains are involved in the interaction, and a polypeptide based on one such sequence inhibits binding. After RNase treatment of Purα enhancement of Tat binding can be partially restored by addition of a single-stranded JCV DNA PUR element, to which Tat does not bind. The results indicate that the Tat-Purα interaction is direct, rather than through an RNA link, and that RNA binding configures Purα for optimal interaction with Tat. (C) 2000 Wiley-Liss, Inc.

Original languageEnglish (US)
Pages (from-to)65-74
Number of pages10
JournalJournal of cellular biochemistry
Volume77
Issue number1
DOIs
StatePublished - 2000
Externally publishedYes

Keywords

  • AIDS
  • JC virus
  • JCV
  • PML
  • Progressive multifocal leukoencephalopathy

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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