Tap /Nxf1 N -Terminal Domain Mediates Homotypic Complex Assembly and Is Necessary for Nuclear RNA Export

Tap/NXF1 is the metazoan nuclear export receptor for both poly (A+) RNA as well as cellular and viral RNAs containing the constitutive transport element (CTE). Tap is a multi-domain protein that interacts directly with nucleoporin proteins of Nuclear Pore Complexes (NPCs) as well as messenger RNA cargo. It has been long understood that the NXF family is unique from the Karyopherin transport receptor family and that RNA export functions independently of the nuclear Ran-GTP gradient. Until now the mechanistic basis for Tap-mediated export has remained elusive; the work herein provides analysis of Tap homotypic complex formation and demonstrates that Tap-mediated export relies on the regulated formation of a Tap homotypic complex. Tap complex formation is mediated by the Tap N-terminal domain, the same region required for Tap-RNP interactions. To observe the functional significance of the Tap complex, constitutively monomeric mutants were generated and found to interact with the components necessary for export: nucleoporins, the export cofactor Nxt1, and RNA. Multimeric Tap is capable of forming interactions with the factors necessary for export but does not prefer binding RNA in the multimeric form, suggesting that multimeric Tap is not actively exporting cargo. Despite this apparent reliance on the Tap monomer for export, constitutively monomeric Tap mutants localize to the nucleus but lack the ability to export RNA. The requirement of the Tap complex for successful export implies that nuclear regulation of Tap complex association and dissociation is necessary prior to exit with cargo. This body of work contains a systematic characterization of the biochemical properties of the Tap protein complex, the basis for Tap complex-RNA interaction and its functional significance in vivo.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Cell and Developmental Biology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Matzat, Leah Helen

Contributors dc:contributor

• Lyne Levesque

• Biology, Molecular

Language dc:language

eng

Identifier

(MiAaPQ)AAI3347446

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/86321