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The mobile nucleoporin Nup2p and chromatin-bound Prp20p function in endogenous NPC-mediated transcriptional control.

Dilworth DJ, Tackett AJ, Rogers RS, Yi EC, Christmas RH, Smith JJ, Siegel AF, Chait BT, Wozniak RW, Aitchison JD - J. Cell Biol. (2005)

Bottom Line: Nuclear pore complexes (NPCs) govern macromolecular transport between the nucleus and cytoplasm and serve as key positional markers within the nucleus.Among these, Nup2p is unique as it transiently associates with NPCs and, when artificially tethered to DNA, can prevent the spread of transcriptional activation or repression between flanking genes, a function termed boundary activity.These data combined with functional assays of boundary activity and epigenetic variegation suggest that Nup2p and the Ran guanylyl-nucleotide exchange factor, Prp20p, interact at specific chromatin regions and enable the NPC to play an active role in chromatin organization by facilitating the transition of chromatin between activity states.

View Article: PubMed Central - PubMed

Affiliation: Institute for Systems Biology, Seattle, WA 98103, USA.

ABSTRACT
Nuclear pore complexes (NPCs) govern macromolecular transport between the nucleus and cytoplasm and serve as key positional markers within the nucleus. Several protein components of yeast NPCs have been implicated in the epigenetic control of gene expression. Among these, Nup2p is unique as it transiently associates with NPCs and, when artificially tethered to DNA, can prevent the spread of transcriptional activation or repression between flanking genes, a function termed boundary activity. To understand this function of Nup2p, we investigated the interactions of Nup2p with other proteins and with DNA using immunopurifications coupled with mass spectrometry and microarray analyses. These data combined with functional assays of boundary activity and epigenetic variegation suggest that Nup2p and the Ran guanylyl-nucleotide exchange factor, Prp20p, interact at specific chromatin regions and enable the NPC to play an active role in chromatin organization by facilitating the transition of chromatin between activity states.

Show MeSH
Dynamic model of NPC-mediated BA. Boundaries (star), marked by Prp20p, are proposed to be mobile but spatially restricted within the nucleus due to their transient Nup2p-dependent association with NPCs. The complexation of DNA with the NPC represents an unstable reaction intermediate from which the DNA can either enter the perinuclear silencing region through Nup60p or detach from the NPC, free to enter the nuclear interior.
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fig7: Dynamic model of NPC-mediated BA. Boundaries (star), marked by Prp20p, are proposed to be mobile but spatially restricted within the nucleus due to their transient Nup2p-dependent association with NPCs. The complexation of DNA with the NPC represents an unstable reaction intermediate from which the DNA can either enter the perinuclear silencing region through Nup60p or detach from the NPC, free to enter the nuclear interior.

Mentions: Endogenous NPC-mediated BA also requires a mechanism for chromatin to associate with the NPC, and we have presented several lines of evidence indicating that the Prp20p–Nup2p interaction provides this critical link. In vitro binding data reveal a robust interaction between Prp20p and Nup2p, but immunopurification and localization data suggest that it is transient in vivo. Thus, we suggest that chromosomal regions interacting with Prp20p attain an equilibrium distribution between subnuclear regions that promote active and silent states, and that these transitions are facilitated through Nup2p-dependent associations with the NPC (Fig. 7). An alternative but not mutually exclusive interpretation of the data is that rather than recruit chromatin to the NPC, Nup2p targets factors important for boundary function from the NPC to specific chromatin sites, thus contributing to boundary maintenance without the requirement of NPC association.


The mobile nucleoporin Nup2p and chromatin-bound Prp20p function in endogenous NPC-mediated transcriptional control.

Dilworth DJ, Tackett AJ, Rogers RS, Yi EC, Christmas RH, Smith JJ, Siegel AF, Chait BT, Wozniak RW, Aitchison JD - J. Cell Biol. (2005)

Dynamic model of NPC-mediated BA. Boundaries (star), marked by Prp20p, are proposed to be mobile but spatially restricted within the nucleus due to their transient Nup2p-dependent association with NPCs. The complexation of DNA with the NPC represents an unstable reaction intermediate from which the DNA can either enter the perinuclear silencing region through Nup60p or detach from the NPC, free to enter the nuclear interior.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171315&req=5

fig7: Dynamic model of NPC-mediated BA. Boundaries (star), marked by Prp20p, are proposed to be mobile but spatially restricted within the nucleus due to their transient Nup2p-dependent association with NPCs. The complexation of DNA with the NPC represents an unstable reaction intermediate from which the DNA can either enter the perinuclear silencing region through Nup60p or detach from the NPC, free to enter the nuclear interior.
Mentions: Endogenous NPC-mediated BA also requires a mechanism for chromatin to associate with the NPC, and we have presented several lines of evidence indicating that the Prp20p–Nup2p interaction provides this critical link. In vitro binding data reveal a robust interaction between Prp20p and Nup2p, but immunopurification and localization data suggest that it is transient in vivo. Thus, we suggest that chromosomal regions interacting with Prp20p attain an equilibrium distribution between subnuclear regions that promote active and silent states, and that these transitions are facilitated through Nup2p-dependent associations with the NPC (Fig. 7). An alternative but not mutually exclusive interpretation of the data is that rather than recruit chromatin to the NPC, Nup2p targets factors important for boundary function from the NPC to specific chromatin sites, thus contributing to boundary maintenance without the requirement of NPC association.

Bottom Line: Nuclear pore complexes (NPCs) govern macromolecular transport between the nucleus and cytoplasm and serve as key positional markers within the nucleus.Among these, Nup2p is unique as it transiently associates with NPCs and, when artificially tethered to DNA, can prevent the spread of transcriptional activation or repression between flanking genes, a function termed boundary activity.These data combined with functional assays of boundary activity and epigenetic variegation suggest that Nup2p and the Ran guanylyl-nucleotide exchange factor, Prp20p, interact at specific chromatin regions and enable the NPC to play an active role in chromatin organization by facilitating the transition of chromatin between activity states.

View Article: PubMed Central - PubMed

Affiliation: Institute for Systems Biology, Seattle, WA 98103, USA.

ABSTRACT
Nuclear pore complexes (NPCs) govern macromolecular transport between the nucleus and cytoplasm and serve as key positional markers within the nucleus. Several protein components of yeast NPCs have been implicated in the epigenetic control of gene expression. Among these, Nup2p is unique as it transiently associates with NPCs and, when artificially tethered to DNA, can prevent the spread of transcriptional activation or repression between flanking genes, a function termed boundary activity. To understand this function of Nup2p, we investigated the interactions of Nup2p with other proteins and with DNA using immunopurifications coupled with mass spectrometry and microarray analyses. These data combined with functional assays of boundary activity and epigenetic variegation suggest that Nup2p and the Ran guanylyl-nucleotide exchange factor, Prp20p, interact at specific chromatin regions and enable the NPC to play an active role in chromatin organization by facilitating the transition of chromatin between activity states.

Show MeSH