Formation of Tap/NXT1 heterodimers activates Tap-dependent nuclear mRNA export by enhancing recruitment to nuclear pore complexes.

Journal Article (Journal Article)

The Tap protein has been shown to activate the nuclear export of mRNA species bearing retroviral constitutive transport elements and is also believed to play an essential role in the sequence nonspecific export of cellular mRNAs. However, it has remained unclear how Tap activity is regulated in vivo. Here, we report that the small NXT1/p15-1 protein functions as a critical cofactor for Tap-mediated mRNA export in both human and invertebrate cells. In the absence of NXT1 binding, the Tap protein is unable to effectively interact with components of the nuclear pore complex and both Tap nucleocytoplasmic shuttling and the nuclear export of mRNA molecules tethered to Tap are therefore severely attenuated. Formation of a Tap/NXT1 heterodimer enhances nucleoporin binding both in vitro and in vivo and induces the formation of a Tap/NXT1/nucleoporin ternary complex that is likely to be a key intermediate in the process of nuclear mRNA export. The critical importance of NXT1 for the nuclear export of poly(A)(+) RNA is emphasized by the finding that specific inhibition of the expression of the Drosophila homolog of human NXT1, by using RNA interference, results in the nuclear accumulation of poly(A)(+) RNA in cultured insect cells. These data suggest that NXT1 may act as a molecular switch that regulates the ability of Tap to mediate nuclear mRNA export by controlling the interaction of Tap with components of the nuclear pore.

Full Text

Duke Authors

Cited Authors

  • Wiegand, HL; Coburn, GA; Zeng, Y; Kang, Y; Bogerd, HP; Cullen, BR

Published Date

  • January 2002

Published In

Volume / Issue

  • 22 / 1

Start / End Page

  • 245 - 256

PubMed ID

  • 11739738

Pubmed Central ID

  • PMC134221

International Standard Serial Number (ISSN)

  • 0270-7306

Digital Object Identifier (DOI)

  • 10.1128/MCB.22.1.245-256.2002


  • eng

Conference Location

  • United States