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: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:The Piwi-interacting RNA (piRNA) pathway is a small RNA-based innate immune system that defends germ cell genomes against transposons. In Drosophila ovaries, the nuclear Piwi protein is required for transcriptional silencing of transposons, though the precise mechanisms by which this occurs are unknown. Here we show that CG9754 is a component of Piwi complexes that functions downstream of Piwi and its binding partner, Asterix, in transcriptional silencing. Enforced tethering of CG9754 protein to nascent mRNA transcripts causes co-transcriptional silencing of the source locus and the deposition of repressive chromatin marks. We have named CG9754 Panoramix, and propose that this protein could act as an adaptor, scaffolding interactions between the piRNA pathway and the general silencing machinery that it recruits to enforce transcriptional repression.