The arginine-rich domains present in human immunodeficiency virus type 1 Tat and Rev function as direct importin beta-dependent nuclear localization signals.

Journal Article

Protein nuclear import is generally mediated by basic nuclear localization signals (NLSs) that serve as targets for the importin alpha (Imp alpha) NLS receptor. Imp alpha is in turn bound by importin beta (Imp beta), which targets the resultant protein complex to the nucleus. Here, we report that the arginine-rich NLS sequences present in the human immunodeficiency virus type 1 regulatory proteins Tat and Rev fail to interact with Imp alpha and instead bind directly to Imp beta. Using in vitro nuclear import assays, we demonstrate that Imp alpha is entirely dispensable for Tat and Rev nuclear import. In contrast, Imp beta proved both sufficient and necessary, in that other beta-like import factors, such as transportin, were unable to support Tat or Rev nuclear import. Using in vitro competition assays, it was demonstrated that the target sites on Imp beta for Imp alpha, Tat, and Rev binding either are identical or at least overlap. The interaction of Tat and Rev with Imp beta is also similar to Imp alpha binding in that it is inhibited by RanGTP but not RanGDP, a finding that may in part explain why the interaction of the Rev nuclear RNA export factor with target RNA species is efficient in the cell nucleus yet is released in the cytoplasm. Together, these studies define a novel class of arginine-rich NLS sequences that are direct targets for Imp beta and that therefore function independently of Imp alpha.

Full Text

Duke Authors

Cited Authors

  • Truant, R; Cullen, BR

Published Date

  • February 1999

Published In

Volume / Issue

  • 19 / 2

Start / End Page

  • 1210 - 1217

PubMed ID

  • 9891055

International Standard Serial Number (ISSN)

  • 0270-7306

Language

  • eng

Conference Location

  • United States