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Caenorhabditis elegans nucleoporins Nup93 and Nup205 determine the limit of nuclear pore complex size exclusion in vivo.

ABSTRACT: Nuclear pore complexes (NPCs) span the nuclear envelope and mediate communication between the nucleus and the cytoplasm. To obtain insight into the structure and function of NPCs of multicellular organisms, we have initiated an extensive analysis of Caenorhabditis elegans nucleoporins. Of 20 assigned C. elegans nucleoporin genes, 17 were found to be essential for embryonic development either alone or in combination. In several cases, depletion of nucleoporins by RNAi caused severe defects in nuclear appearance. More specifically, the C. elegans homologs of vertebrate Nup93 and Nup205 were each found to be required for normal NPC distribution in the nuclear envelope in vivo. Depletion of Nup93 or Nup205 caused a failure in nuclear exclusion of nonnuclear macromolecules of approximately 70 kDa without preventing active nuclear protein import or the assembly of the nuclear envelope. The defects in NPC exclusion were accompanied by abnormal chromatin condensation and early embryonic arrest. Thus, the contribution to NPC structure of Nup93 and Nup205 is essential for establishment of normal NPC function and for cell viability.

SUBMITTER: Galy V

PROVIDER: S-EPMC284812 | biostudies-literature | 2003 Dec

REPOSITORIES: biostudies-literature

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Caenorhabditis elegans nucleoporins Nup93 and Nup205 determine the limit of nuclear pore complex size exclusion in vivo.

Galy Vincent V Mattaj Iain W IW Askjaer Peter P

Molecular biology of the cell 20030822 12

Nuclear pore complexes (NPCs) span the nuclear envelope and mediate communication between the nucleus and the cytoplasm. To obtain insight into the structure and function of NPCs of multicellular organisms, we have initiated an extensive analysis of Caenorhabditis elegans nucleoporins. Of 20 assigned C. elegans nucleoporin genes, 17 were found to be essential for embryonic development either alone or in combination. In several cases, depletion of nucleoporins by RNAi caused severe defects in nuc ...[more]

PMID: 12937276

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Project description:BackgroundThe nuclear pore complex (NPC) mediates nuclear transport of RNA and proteins into and out of the nucleus. Certain nucleoporins have additional functions in chromatin organization and transcription regulation. Nup93 is a scaffold nucleoporin at the nuclear pore complex which is associated with human chromosomes 5, 7 and 16 and with the promoters of the HOXA gene as revealed by ChIP-on-chip studies using tiling microarrays for these chromosomes. However, the functional consequences of the association of Nup93 with HOXA is unknown.ResultsHere, we examined the association of Nup93 with the HOXA gene cluster and its consequences on HOXA gene expression in diploid colorectal cancer cells (DLD1). Nup93 showed a specific enrichment ~1 Kb upstream of the transcription start site of each of the HOXA1, HOXA3 and HOXA5 promoters, respectively. Furthermore, the association of Nup93 with HOXA was assisted by its interacting partners Nup188 and Nup205. The depletion of the Nup93 sub-complex significantly upregulated HOXA gene expression levels. However, expression levels of a control gene locus (GLCCI1) on human chromosome 7 were unaffected. Three-dimensional fluorescence in situ hybridization (3D-FISH) analyses revealed that the depletion of the Nup93 sub-complex (but not Nup98) disengages the HOXA gene locus from the nuclear periphery, suggesting a potential role for Nup93 in tethering and repressing the HOXA gene cluster. Consistently, Nup93 knockdown increased active histone marks (H3K9ac), decreased repressive histone marks (H3K27me3) on the HOXA1 promoter and increased transcription elongation marks (H3K36me3) within the HOXA1 gene. Moreover, the combined depletion of Nup93 and CTCF (a known organizer of HOXA gene cluster) but not Nup93 alone, significantly increased GLCCI1 gene expression levels. Taken together, this suggests a novel role for Nup93 and its interactors in repressing the HOXA gene cluster.ConclusionsThis study reveals that the nucleoporin Nup93 assisted by its interactors Nup188 and Nup205 mediates the repression of HOXA gene expression.

Dataset Information

Caenorhabditis elegans nucleoporins Nup93 and Nup205 determine the limit of nuclear pore complex size exclusion in vivo.

Publications

Caenorhabditis elegans nucleoporins Nup93 and Nup205 determine the limit of nuclear pore complex size exclusion in vivo.

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