Biology subjects

Schirmeisen, K.

Publications and source records attributed to Schirmeisen, K..

3 recordsLinked to original sources

bioRxiv2024

The fission yeast SUMO-targeted Ubiquitin Ligase Slx8 functionally associates with clustered centromeres and the silent mating type region at the nuclear periphery

The SUMO-targeted Ubiquitin ligase (STUbL) family is involved in multiple cellular processes via a wide range of mechanisms to maintain genome stability. One of the evolutionarily conserved functions of STUbL is to promote changes in the nuclear positioning of DNA lesions, targeting them to the nuclear periphery. In Schizossacharomyces pombe, the STUbL Slx8 is a regulator of SUMOylated proteins and promotes replication stress tolerance by counteracting the toxicity of SUMO conjugates. In order to study the dynamic dialectic between Ubiquitinylation and SUMOylation in the nuclear space of the S. pombe genome, we analyzed Slx8 localization. Unexpectedly, we did not detect replication stress-induced Slx8 foci. However, we discovered that Slx8 forms a single nuclear focus, enriched at the nuclear periphery, which marks both clustered centromeres at the spindle pole body and the silent mating type region. The formation of this single Slx8 focus requires the E3 SUMO ligase Pli1, poly-SUMOylation and the histone methyl transferase Clr4 that is responsible for the heterochromatin histone mark H3-K9 methylation. Finally, we established that Slx8 promotes centromere clustering and gene silencing at heterochromatin domains. Altogether, our data highlight evolutionarily conserved and functional relationships between STUbL and heterochromatin domains to promote gene silencing and nuclear organization. HighlightsO_LIThe S. pombe STUbL Slx8 forms a single nuclear focus enriched at the nuclear periphery in a SUMO-chain-dependent manner. C_LIO_LISlx8 foci mark clustered centromeres and the silenced mating type region but not telomeres. C_LIO_LIH3-K9 methylation by Crl4 promotes the single nuclear Slx8 focus C_LIO_LISlx8 promotes centromere clustering and gene silencing. C_LI

cell biology↗

bioRxiv2023

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

Nuclear pores complexes (NPCs) are genome organizers, defining a particular nuclear compartment enriched for SUMO protease and proteasome activities, and acting 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 progression of restarted DNA polymerase. In contrast to Ulp1-dependent events, 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 RDR dynamics in distinct ways. Our work probes the mechanisms by which the NPC environment ensures optimal RDR. Highlights[bullet] Ulp1-associated NPCs ensure efficient initiation of restarted DNA synthesis, in a SUMO chain-dependent manner [bullet]Proteasome-associated NPCs foster the progression of restarted DNA synthesis, in a SUMO chain-independent manner [bullet]The nucleoporin Nup60 promotes the spatial sequestration of Ulp1 at the nuclear periphery [bullet]Ulp1 and proteasome activities are differently required for optimal recombination-mediated fork restart.

molecular biology↗

bioRxiv2019

S. pombe DNA translocases Rrp1 and Rrp2 have distinct roles at centromeres and telomeres that ensure genome stability.

Homologous recombination (HR) is a DNA repair mechanism that ensures, together with heterochromatin machinery, the proper replication, structure and function of telomeres and centromeres that is essential for the maintenance of genome integrity. Schizosaccharomyces pombe Rrp1 and Rrp2 participate in HR and are orthologues of Saccharomyces cerevisiae Uls1, a SWI2/SNF2 DNA translocase and SUMO-Targeted Ubiquitin Ligase. We show that Rrp1 or Rrp2 upregulation leads to chromosome instability and growth defects. These phenotypes depend on putative DNA translocase activities of Rrp1 and Rrp2. Either Rrp1 or Rrp2 overproduction results in a reduction in global histone levels, suggesting that Rrp1 and Rrp2 may modulate nucleosome dynamics. In addition we show that Rrp2, but not Rrp1, acts at telomeres. We propose that this role depends on the previously described interaction between Rrp2 and Top2. We conclude that Rrp1 and Rrp2 have important roles for centromere and telomere function and maintenance, contributing to the preservation of genome stability during vegetative cell growth.\n\nSUMMARY STATEMENTSchizosaccharomyces pombe DNA translocases Rrp1 and Rrp2 modulate centromere and telomere maintenance pathways and dysregulation of their activity leads to genome instability.

cell biology↗