Dataset Information

NXF1/p15 heterodimers are essential for mRNA nuclear export in Drosophila.

ABSTRACT: The conserved family of NXF proteins has been implicated in the export of messenger RNAs from the nucleus. In metazoans, NXFs heterodimerize with p15. The yeast genome encodes a single NXF protein (Mex67p), but there are multiple nxf genes in metazoans. Whether metazoan NXFs are functionally redundant, or their multiplication reflects an adaptation to a greater substrate complexity or to tissue-specific requirements has not been established. The Drosophila genome encodes one p15 homolog and four putative NXF proteins (NXF1 to NXF4). Here we show that depletion of the endogenous pools of NXF1 or p15 from Drosophila cells inhibits growth and results in a rapid and robust accumulation of polyadenylated RNAs within the nucleus. Fluorescence in situ hybridizations show that export of both heat-shock and non-heat-shock mRNAs, as well as intron-containing and intronless mRNAs is inhibited. Depleting endogenous NXF2 or NXF3 has no apparent phenotype. Moreover, NXF4 is not expressed at detectable levels in cultured Drosophila cells. We conclude that Dm NXF1/p15 heterodimers only (but not NXF2-NXF4) mediate the export of the majority of mRNAs in Drosophila cells and that the other members of the NXF family play more specialized or different roles.

SUBMITTER: Herold A

PROVIDER: S-EPMC1370216 | biostudies-other | 2001 Dec

REPOSITORIES: biostudies-other

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NXF1/p15 heterodimers are essential for mRNA nuclear export in Drosophila.

Herold A A Klymenko T T Izaurralde E E

RNA (New York, N.Y.) 20011201 12

The conserved family of NXF proteins has been implicated in the export of messenger RNAs from the nucleus. In metazoans, NXFs heterodimerize with p15. The yeast genome encodes a single NXF protein (Mex67p), but there are multiple nxf genes in metazoans. Whether metazoan NXFs are functionally redundant, or their multiplication reflects an adaptation to a greater substrate complexity or to tissue-specific requirements has not been established. The Drosophila genome encodes one p15 homolog and four ...[more]

PMID: 11780633

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Project description:In eukaryotic cells, different RNA species are exported from the nucleus via specialized pathways. The mRNA export machinery is highly integrated with mRNA processing, and includes a different set of nuclear transport adaptors as well as other mRNA binding proteins, RNA helicases, and NPC-associated proteins. The protozoan parasite Trypanosoma cruzi is the causative agent of Chagas disease, a widespread and neglected human disease which is endemic to Latin America. Gene expression in Trypanosoma has unique characteristics, such as constitutive polycistronic transcription of protein-encoding genes and mRNA processing by trans-splicing. In general, post-transcriptional events are the major points for regulation of gene expression in these parasites. However, the export pathway of mRNA from the nucleus is poorly understood. The present study investigated the function of TcSub2, which is a highly conserved protein ortholog to Sub2/ UAP56, a component of the Transcription/Export (TREX) multiprotein complex connecting transcription with mRNA export in yeast/human. Similar to its orthologs, TcSub2 is a nuclear protein, localized in dispersed foci all over the nuclei -except the fibrillar center of nucleolus- and at the interface between dense and non-dense chromatin areas, proposing the association of TcSub2 with transcription/processing sites. These findings were analyzed further by BrUTP incorporation assays and confirmed that TcSub2 is physically associated with active RNA polymerase II (RNA pol II), but not RNA polymerase I (RNA pol I) or Spliced Leader (SL) transcription, demonstrating participation particularly in nuclear mRNA metabolism in T. cruzi. The double knockout of the TcSub2 gene is lethal in T. cruzi, suggesting it has an essential function. Alternatively, RNA interference assays were performed in Trypanosoma brucei. It allowed demonstrating that besides being an essential protein, its knockdown causes mRNA accumulation in the nucleus and decrease of translation levels, reinforcing that Trypanosoma-Sub2 (Tryp-Sub2) is a component of mRNA transcription/export pathway in trypanosomes.

Dataset Information

NXF1/p15 heterodimers are essential for mRNA nuclear export in Drosophila.

Publications

NXF1/p15 heterodimers are essential for mRNA nuclear export in Drosophila.

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