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SUMO protease and proteasome recruitment at the nuclear periphery differently affect replication dynamics at arrested forks.

ABSTRACT: Nuclear pores complexes (NPCs) are genome organizers, defining a particular nuclear compartment enriched for SUMO protease and proteasome activities, and act as docking sites for DNA repair. In fission yeast, the anchorage of perturbed replication forks to NPCs is an integral part of the recombination-dependent replication restart mechanism (RDR) that resumes DNA synthesis at terminally dysfunctional forks. By mapping DNA polymerase usage, we report that SUMO protease Ulp1-associated NPCs ensure efficient initiation of restarted DNA synthesis, whereas proteasome-associated NPCs sustain the speed of restarted DNA polymerase. In contrast to Ulp1, this last function occurs independently of SUMO chains formation. By analyzing the role of the nuclear basket, the nucleoplasmic extension of the NPC, we reveal that the activities of Ulp1 and the proteasome cannot compensate for each other and affect the dynamics of RDR in distinct ways. Our work probes the mechanisms by which the NPC environment ensures optimal RDR.

ORGANISM(S): Schizosaccharomyces pombe

PROVIDER: GSE247371 | GEO | 2023/11/13

REPOSITORIES: GEO

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A R-loop sensing pathway mediates the relocation of transcribed genes to nuclear pore complexes

Project description:Nuclear organization has emerged as a critical player in the control of genomic processes, including transcription. In this context, nuclear pore complexes (NPCs) have increasingly recognized interactions with the genome, as exemplified in yeast, where they bind inducible genes and damaged genomic regions, positively impacting their fate. To investigate the pathways fostering chromatin association with NPCs, we have combined genome-wide approaches with live imaging of individually-tagged model loci. Strikingly, ChIP-seq analyses of NPC-bound genes revealed a strong correlation between pore association and the propensity to accumulate co-transcriptional R-loops, which are genotoxic structures forming through hybridization of nascent RNAs with their DNA templates. Manipulating cis- or trans-acting regulators of hybrid formation further demonstrated that R-loop accumulation per se, rather than high transcription or R-loop-associated genetic instability, is the primary trigger for relocation to NPCs. Mechanistically, R-loop-dependent repositioning involves the recognition of displaced ssDNA moieties by the ssDNA-binding protein RPA, and SUMO-dependent interactions between RPA and NPC-associated factors. Preventing R-loop-dependent NPC localization leads to lethality, while permanent NPC tethering of a model hybrid-prone sequence attenuates R-loop-dependent genetic instability. Remarkably, this novel relocation pathway involves similar molecular factors as those required for the association of stalled replication forks or eroded telomeres with NPCs, suggesting the existence of convergent mechanisms for sensing transcriptional and genotoxic stresses.

2023-08-21 | GSE225324 | GEO

Nuclear transport surveillance of p53 by nuclear pores in glioblastoma

Project description:Nuclear pore complexes (NPCs) are the central apparatus of nucleocytoplasmic transport. Disease-specific alterations of NPCs contribute to the pathogenesis of many cancers; however, the roles of NPCs in glioblastoma (GBM) are unknown. In this study, we report genomic amplification of NUP107, a component of NPCs, in GBM and show that NUP107 is overexpressed simultaneously with MDM2, a critical E3 ligase that mediates p53 degradation. Depletion of NUP107 inhibits the growth of GBM cell lines through p53 protein stabilization. Mechanistically, NPCs establish a p53 degradation platform via an export pathway coupled with 26S proteasome tethering. NUP107 is the keystone for NPC assembly; the loss of NUP107 affects the integrity of the NPC structure, and thus the proportion of 26S proteasome in the vicinity of nuclear pores significantly decreases. Together, our findings establish roles of NPCs in transport surveillance and provide insights into p53 inactivation in GBM.

2023-08-19 | GSE216888 | GEO

Multifaceted down-regulation of the Srs2 helicase by the SUMO-like domain protein Esc2 promotes local recombination at sites of stalled replication

Project description:The SUMO-like domains-containing family of proteins to which Saccharomyces cerevisiae Esc2 belongs facilitates DNA damage tolerance (DDT) via elusive mechanisms. Here we report that Esc2 promotes recombination-mediated DDT by engaging in functional and physical interactions with Srs2 and Elg1, two readers of SUMOylated PCNA and modulators of DDT. These interactions depend on the SUMO Interacting Motifs of Elg1 and Srs2, and on the SUMO-like domains of Esc2. Mechanistically, Esc2 promotes Elg1 association to damaged and stalled forks and Srs2 turnover. Elg1 limits the levels of SUMOylated PCNA and subsequently of the anti-recombinase Srs2 at damaged sites, upholding local Rad51 binding. In conjunction with the SUMO–targeted ubiquitin ligase Slx5/Slx8, Esc2 also promotes proteasome-mediated Srs2 turnover, a process further enhanced by CDK-mediated Srs2 phosphorylation. Our results provide mechanistic insights into how SUMO- and DNA damage response-regulated pathways intersect to enable local error-free damage-bypass by recombination in the face of genotoxic stress. Proteins ChIP-chip analyses analysis were carried out as described (Bermejo et al., 2009). Labelled probes were hybridized to Affymetrix S.cerevisiae Tiling 1.0 (P/N 900645) arrays and processed with TAS software.

2015-02-16 | E-GEOD-65701 | biostudies-arrayexpress

Selective autophagy degrades nuclear pore complexes

Project description:Nuclear pore complexes (NPCs) are giant cylindrical structures embedded into the nuclear envelope and mediate nucleocytoplasmic exchange. NPC longevity has been linked to aging but since they appear to rarely turn over, the underlying mechanisms remain understudied. Here, we show that upon nitrogen starvation and genetic interference with NPC architecture, Nups are rapidly degraded in budding yeast. We demonstrate that NPC turnover involves 25 vacuolar proteases and the core autophagic machinery. Autophagic degradation is mediated by the cytoplasmically exposed Nup159 that serves as intrinsic cargo receptor and directly binds to the autophagic marker protein Atg8. The inducible manner of this mechanism might explain why NPCs are long-lived under specific conditions

2019-11-13 | PXD011571 | Pride

Replication dynamics of recombination-dependent replication forks: leading and lagging strand synthesis are not coupled

Project description:DNA replication fidelity is essential for maintaining genetic stability. Forks arrested at replication fork barriers can be stabilised by the intra-S phase checkpoint, subsequently being rescued by a converging fork, or resuming when the barrier is removed. However, some arrested forks cannot be stabilised and fork convergence cannot rescue in all situations. Thus, cells have developed homologous recombination-dependent mechanisms to restart persistently inactive forks. To understand the dynamics of HR-restart, we visualized in vivo replication dynamics at an S. pombe replication barrier, RTS1, using polymerase usage sequencing and model replication dynamics by Monte Carlo simulation. We confirm that HR-restarted forks synthesise both strands with Pol d and that Pol a is not used significantly on either strand: the lagging strand template remains as a gap that is filled in later. We further demonstrate that HR-restarted forks progress for >30 kb kilobases without maturing to a d/e configuration and can progress through a fork barrier that arrests canonical forks. Finally, by manipulating lagging strand resection during HR-restart by deleting pku70, we show that the leading strand initiates replication at the same position, demonstrating the stability of the 3' single strand in the context of increased resection.

2020-07-03 | GSE153731 | GEO

Nuclear pore complexes mediate subtelomeric gene silencing by regulating PCNA levels on chro atin

Project description:The nuclear pore complex (NPC) physically interacts with chromatin and regulates gene expression. The Saccharomyces cerevisiae inner ring nucleoporin Nup170 has been implicated in chromatin organization and the maintenance of gene silencing in subtelomeric regions. To gain insight into how Nup170 regulates this process, we used protein-protein interactions, genetic interactions, and transcriptome correlation analyses to identify the Ctf18-RFC complex, an alternative proliferating cell nuclear antigen (PCNA) loader, as a facilitator of the gene regulatory functions of Nup170. The Ctf18-RFC complex is recruited to a subpopulation of NPCs that lack the nuclear basket proteins Mlp1 and Mlp2. In the absence of Nup170, PCNA levels on DNA are reduced, resulting in the loss of silencing of subtelomeric genes. Increasing PCNA levels on DNA by removing Elg1, which is required for PCNA unloading, rescues subtelomeric silencing defects in nup170Δ. The NPC therefore mediates subtelomeric gene silencing by regulating PCNA levels on DNA.

2023-06-13 | PXD041496 | Pride

Pre-assembled Nuclear Pores Insert into the Nuclear Envelope During Early Development

Project description:Nuclear Pore Complexes (NPCs) span the nuclear envelope (NE) and mediate nucleocytoplasmic transport. In metazoan oocytes and early embryos, NPCs not only reside within the NE but also at some endoplasmatic reticulum (ER) membrane sheets, termed annulate lamellae (AL). Although a role for AL as NPC storage pools has been discussed, it remains controversial if and how they contribute to the NPC density at the NE. Here we show that AL insert into the NE as the ER feeds rapid nuclear expansion in Drosophila blastoderm embryos. We demonstrate that NPCs within AL resemble pore scaffolds that mature only upon insertion into the NE. We delineate a topological model in which NE openings are critical for AL uptake that nevertheless occurs without compromising the permeability barrier of the NE. We finally show that this unanticipated mode of pore insertion is developmentally regulated and operates prior to gastrulation.

2016-07-12 | PXD004120 | Pride

High-precision mapping of nuclear pore-chromatin interactions reveals new principles of genome organization at the nuclear envelope

Project description:The role of nuclear pore complexes (NPCs) in genome organization remains poorly characterized due to technical limitations in probing genome-wide protein-DNA interactions that are specific to the nuclear envelope. Here, we developed a sensitive method, NPC-DamID, which combines in vitro reconstitution of nuclear import and DamID technology. This fixation-free method specifically identifies genomic DNA interactions at the NPCs in intact nuclei. We found that NPCs are preferentially associated with common and hierarchically arranged super-enhancers (SEs) across multiple cells and tissue types. We also uncovered phase-separated condensates at NPCs that compartmentalize and concentrate transcriptional coactivators and structural proteins at SE-regulated genes. Our results support the idea that NPCs are sites of anchoring SE regulatory hubs through their interaction with CTCF and also maintains the conformation of SEs through interaction with structural proteins of SEs like Med1 and PolII.

2021-08-02 | GSE176106 | GEO

A role for the nucleoporin Nup170p in chromatin structure and gene silencing [Agilent ChIP-chip]

Project description:Embedded in the nuclear envelope, nuclear pore complexes (NPCs) not only regulate nuclear transport, but also interface with both transcriptionally active euchromatin and largely silenced heterochromatin, as well as the boundaries between these regions. It is unclear what functional role NPCs play in establishing or maintaining these distinct chromatin domains. Here we report that the yeast NPC protein Nup170p interacts with specific regions of the genome containing ribosomal protein and subtelomeric genes. At these locations, Nup170p functions to establish normal nucleosome positioning and as a repressor of transcription. We show that the function of Nup170p in subtelomeric gene silencing is linked to its association with the RSC chromatin-remodeling complex and the silencing factor Sir4p, and that the binding of Nup170p and Sir4p to subtelomeric chromatin is cooperative and necessary for the association of telomeres with the nuclear envelope. Our results establish the NPC as an active participant in the formation of peripheral heterochromatin. The genome-wide localization profiles of Nup170p and Nup157p were determined by chromatin immunoprecipitation and DNA microarray analysis using agilent whole genome Saccharomyces cerevisiae arrays. In addition, the localization profile of Nup170p was determined in sir4∆ and yku70∆ strains.

2013-02-28 | E-GEOD-36794 | biostudies-arrayexpress

DamID LaminB1 data in mouse MEFs, wild-type and POU2F1-/-. DamID LaminA data in mouse Neural Precursor Cells and Astrocytes.

Project description:DamID LaminB1 data were generated in POU2F1-/- MEFs to study the potential role of POU2F1/Oct1 in genome - nuclear lamina interactions. DamID LaminA data were generated in NPCs and Astrocytes to study similarities/differences between LaminA and LaminB1 binding. Comparison of MEF wt versus MEF POU2F1-/-. Comparison of LaminA (NPC & AC) with LaminB1 (NPC & AC data in GSE17051)

2012-10-10 | E-GEOD-36132 | biostudies-arrayexpress

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