Project description:Cells are often exposed to physical or chemical stresses that can damage the structures of essential biomolecules. Stress-induced cellular damage can become deleterious if not managed appropriately. Rapid and adaptive responses to stresses are therefore crucial for cell survival. In eukaryotic cells, different stresses trigger post-translational modification of proteins with the small ubiquitin-like modifier SUMO. However, the specific regulatory roles of sumoylation in each stress response are not well understood. Here, we examined the sumoylation events that occur in budding yeast after exposure to hyperosmotic stress. We discovered by proteomic and biochemical analyses that hyperosmotic stress incurs the rapid and transient sumoylation of Cyc8 and Tup1, which together form a conserved transcription corepressor complex that regulates hundreds of genes. Gene expression and cell biological analyses revealed that sumoylation of each protein directs distinct outcomes. In particular, we discovered that Cyc8 sumoylation prevents the persistence of hyperosmotic stress-induced Cyc8-Tup1 inclusions, which involves a glutamine-rich prion domain in Cyc8. We propose that sumoylation protects against persistent inclusion formation during hyperosmotic stress, allowing optimal transcriptional function of the Cyc8-Tup1 complex.
Project description:Nuclear Argonaute proteins, guided by small RNAs, mediate sequence-specific heterochromatin formation. The molecular principles that link Argonaute–small RNA complexes, once bound to a nascent target RNA, to general heterochromatin effectors are poorly understood. Here, we uncover the mechanistic basis of how the PIWI interacting RNA (piRNA) pathway engages the heterochromatin machinery in Drosophila. Piwi-mediated recruitment of the corepressor complex SFiNX to chromatin leads to SUMOylation of its Panoramix subunit. SUMOylation, together with a hydrophobic LxxLL motif in the intrinsically disordered repressor domain of Panoramix, are necessary and sufficient to recruit Small ovary (Sov), a multi-zinc finger protein essential for general heterochromatin formation and viability. Structure-guided mutations that abrogate the Panoramix-Sov interaction or that prevent Panoramix SUMOylation uncouple Sov from the piRNA pathway, resulting in viable but sterile flies that exhibit de-repression of Piwi-targeted transposons. Thus, coupling the piRNA-guided recruitment of a corepressor to chromatin with its SUMOylation underlies sequence-specific heterochromatin formation.
Project description:Nuclear Argonaute proteins, guided by small RNAs, mediate sequence-specific heterochromatin formation. The molecular principles that link Argonaute–small RNA complexes, once bound to a nascent target RNA, to general heterochromatin effectors are poorly understood. Here, we uncover the mechanistic basis of how the PIWI interacting RNA (piRNA) pathway engages the heterochromatin machinery in Drosophila. Piwi-mediated recruitment of the corepressor complex SFiNX to chromatin leads to SUMOylation of its Panoramix subunit. SUMOylation, together with a hydrophobic LxxLL motif in the intrinsically disordered repressor domain of Panoramix, are necessary and sufficient to recruit Small ovary (Sov), a multi-zinc finger protein essential for general heterochromatin formation and viability. Structure-guided mutations that abrogate the Panoramix-Sov interaction or that prevent Panoramix SUMOylation uncouple Sov from the piRNA pathway, resulting in viable but sterile flies that exhibit de-repression of Piwi-targeted transposons. Thus, coupling the piRNA-guided recruitment of a corepressor to chromatin with its SUMOylation underlies sequence-specific heterochromatin formation.
Project description:Nuclear Argonaute proteins, guided by small RNAs, mediate sequence-specific heterochromatin formation. The molecular principles that link Argonaute–small RNA complexes, once bound to a nascent target RNA, to general heterochromatin effectors are poorly understood. Here, we uncover the mechanistic basis of how the PIWI interacting RNA (piRNA) pathway engages the heterochromatin machinery in Drosophila. Piwi-mediated recruitment of the corepressor complex SFiNX to chromatin leads to SUMOylation of its Panoramix subunit. SUMOylation, together with a hydrophobic LxxLL motif in the intrinsically disordered repressor domain of Panoramix, are necessary and sufficient to recruit Small ovary (Sov), a multi-zinc finger protein essential for general heterochromatin formation and viability. Structure-guided mutations that abrogate the Panoramix-Sov interaction or that prevent Panoramix SUMOylation uncouple Sov from the piRNA pathway, resulting in viable but sterile flies that exhibit de-repression of Piwi-targeted transposons. Thus, coupling the piRNA-guided recruitment of a corepressor to chromatin with its SUMOylation underlies sequence-specific heterochromatin formation.
Project description:Nuclear Argonaute proteins, guided by small RNAs, mediate sequence-specific heterochromatin formation. The molecular principles that link Argonaute–small RNA complexes, once bound to a nascent target RNA, to general heterochromatin effectors are poorly understood. Here, we uncover the mechanistic basis of how the PIWI interacting RNA (piRNA) pathway engages the heterochromatin machinery in Drosophila. Piwi-mediated recruitment of the corepressor complex SFiNX to chromatin leads to SUMOylation of its Panoramix subunit. SUMOylation, together with a hydrophobic LxxLL motif in the intrinsically disordered repressor domain of Panoramix, are necessary and sufficient to recruit Small ovary (Sov), a multi-zinc finger protein essential for general heterochromatin formation and viability. Structure-guided mutations that abrogate the Panoramix-Sov interaction or that prevent Panoramix SUMOylation uncouple Sov from the piRNA pathway, resulting in viable but sterile flies that exhibit de-repression of Piwi-targeted transposons. Thus, coupling the piRNA-guided recruitment of a corepressor to chromatin with its SUMOylation underlies sequence-specific heterochromatin formation.
Project description:During meiosis, crossover recombination is essential to link homologous chromosomes and drive faithful chromosome segregation. Crossover recombination is non-random across the genome, and centromere-proximal crossovers are associated with an increased risk of aneuploidy, including Trisomy 21 in humans. Here, we identify the conserved Ctf19/CCAN kinetochore sub-complex as a major factor that minimizes potentially deleterious centromere-proximal crossovers in budding yeast. We uncover multi-layered suppression of pericentromeric recombination by the Ctf19 complex, operating across distinct chromosomal distances. The Ctf19 complex prevents meiotic DNA break formation, the initiating event of recombination, proximal to the centromere. The Ctf19 complex independently drives the enrichment of cohesin throughout the broader pericentromere to suppress crossovers, but not DNA breaks. This non-canonical role of the kinetochore in defining a chromosome domain that is refractory to crossovers adds a new layer of functionality by which the kinetochore prevents the incidence of chromosome segregation errors that generate aneuploid gametes. Two samples total: two biological replicate Spo11-oligo maps of S. cerevisiae SK1 mcm21 null mutant
Project description:During meiosis, crossover recombination is essential to link homologous chromosomes and drive faithful chromosome segregation. Crossover recombination is non-random across the genome, and centromere-proximal crossovers are associated with an increased risk of aneuploidy, including Trisomy 21 in humans. Here, we identify the conserved Ctf19/CCAN kinetochore sub-complex as a major factor that minimizes potentially deleterious centromere-proximal crossovers in budding yeast. We uncover multi-layered suppression of pericentromeric recombination by the Ctf19 complex, operating across distinct chromosomal distances. The Ctf19 complex prevents meiotic DNA break formation, the initiating event of recombination, proximal to the centromere. The Ctf19 complex independently drives the enrichment of cohesin throughout the broader pericentromere to suppress crossovers, but not DNA breaks. This non-canonical role of the kinetochore in defining a chromosome domain that is refractory to crossovers adds a new layer of functionality by which the kinetochore prevents the incidence of chromosome segregation errors that generate aneuploid gametes.
Project description:SUMOylation is an essential and highly dynamic post-translational modification that regulates developmental processes and stress adaptations in plants to environmental cues. The global SUMOylation is quickly induced by dehydration and hyperosmotic stresses in plants, while the detailed mechanism underlying such SUMOylation dynamics is largely unknown. Herein, we report key components in osmotic stress and abscisic acid signaling, SNF1-related protein kinase 2s (SnRK2s), phosphorylate SUMO E3 ligase SAP and MIZ1-1 (SIZ1) to stabilize SIZ1 protein under stress conditions. The Ser820 residue is a functional SnRK2 phosphosite and non-phosphorylatable SIZ1S820A is unstable in vivo and in vitro. Under osmotic stress, the rapidly activated protein kinases SnRK2.4 and SnRK2.6 can phosphorylate SIZ1, which enhances the stability of SIZ1, and participates in the response to osmotic stress. However, the instability of SIZ1S820A protein was independent of COP1, indicating that there might be a new degradation mechanism for SIZ1. Our studies suggest that SnRK2s induced phosphorylation regulates SIZ1 stability to precisely modulates SUMOylation dynamics upon osmotic stresses. Additionally, such a reciprocal regulation by SnRK2 and COP1 might be a general regulation machinery that controls the stability of dozens of proteins.