Selective nuclear export of specific classes of mRNA from mammalian nuclei is promoted by GANP.

Vihandha O Wickramasinghe,John B Gurdon,Ronald A Laskey,Murray Stewart,Robert Andrews,Peter Ellis,Ashok R Venkitaraman,Cordelia Langford

doi:10.1093/nar/gku095

Vihandha O Wickramasinghe, John B Gurdon + Show 6 more

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https://doi.org/10.1093/nar/gku095

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Journal: Nucleic acids research	Publication Date: Feb 6, 2014
Citations: 64	License type: CC BY 3.0

Affiliation: University of Cambridge

Abstract

The nuclear phase of the gene expression pathway culminates in the export of mature messenger RNAs (mRNAs) to the cytoplasm through nuclear pore complexes. GANP (germinal- centre associated nuclear protein) promotes the transfer of mRNAs bound to the transport factor NXF1 to nuclear pore complexes. Here, we demonstrate that GANP, subunit of the TRanscription-EXport-2 (TREX-2) mRNA export complex, promotes selective nuclear export of a specific subset of mRNAs whose transport depends on NXF1. Genome-wide gene expression profiling showed that half of the transcripts whose nuclear export was impaired following NXF1 depletion also showed reduced export when GANP was depleted. GANP-dependent transcripts were highly expressed, yet short-lived, and were highly enriched in those encoding central components of the gene expression machinery such as RNA synthesis and processing factors. After injection into Xenopus oocyte nuclei, representative GANP-dependent transcripts showed faster nuclear export kinetics than representative transcripts that were not influenced by GANP depletion. We propose that GANP promotes the nuclear export of specific classes of mRNAs that may facilitate rapid changes in gene expression.

Highlights

Nuclear export of messenger RNA is mediated by transport factors that bind to mature messenger RNAs (mRNAs) and enable them to overcome the barrier function within the nuclear pore complex (NPC) transport channel generated by nuclear pore proteins that have regions rich in phenylalanine-glycine repeats (FG-nucleoporins) [1,2,3,4,5,6]
When the nuclearcytoplasmic distribution of poly(A)+RNA following germinal- centre associated nuclear protein (GANP) or NXF1 depletion was examined using a Cy3labelled oligo-dT probe, an increase in the nuclear to cytoplasmic ratio of poly(A)+RNA compared with control siRNA-treated cells was observed in each case
The difference was more pronounced with NXF1 depletion and was observed 48 h following NXF1 depletion, whereas a similar defect was not observed until 72 h following GANP depletion (Figure 1B and Supplementary Figure S1)

Summary

Introduction

Nuclear export of messenger RNA (mRNA) is mediated by transport factors that bind to mature mRNAs and enable them to overcome the barrier function within the nuclear pore complex (NPC) transport channel generated by nuclear pore proteins that have regions rich in phenylalanine-glycine repeats (FG-nucleoporins) [1,2,3,4,5,6]. The export of some transcripts, such as those from the GAL genes, is tightly coupled to preceding steps in the gene expression pathway by the Sac3-containing TREX-2 complex [3,15,16] that localizes these actively transcribing genes to the NPCs [17,18]. Mammalian cells have an analogous complex, based on a scaffold of the Sac homologue germinal- centre associated nuclear protein (GANP), preliminary evidence suggested that this complex appears to function primarily to facilitate the movement of mature transcripts from processing centres deeper in the nucleus to the NPCs [19,20].

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