Project description:The Piwi protein Mili and the Piwi-interacting RNA (piRNA) pathway are required to establish L1 DNA methylation during epigenetic reprogramming that accompanies male germ cell development. Although Mili is expressed throughout most of adult spermatogenesis, its function therein remains unknown. We find that Mili displays a hitherto unappreciated dynamic expression profile during spermatogenesis, expressed in the mitotic spermatogonia but absent at the early meiotic stages only to reappear in late zygotene spermatocytes. Here we show using conditional mutagenesis that Mili's endonuclease activity post-transcriptionally cleaves L1 transcripts commencing upon its reappearance in late zygotene spermatocytes even in the presence of normal L1 DNA methylation
Project description:This SuperSeries is composed of the following subset Series: GSE32180: MIWI catalysis is required for piRNA amplification-independent LINE1 transposon silencing [microarray] GSE32184: MIWI catalysis is required for piRNA amplification-independent LINE1 transposon silencing [deep sequencing] Refer to individual Series
Project description:The PIWI-interacting RNA (piRNA) pathway guides the DNA methylation of young active transposons during male mouse germline development. piRNAs tether the PIWI protein MIWI2 (PIWIL4) to the nascent transposon transcript that results in DNA methylation through SPOCD1. Transposon methylation requires exacting precision: all copies need to be methylated yet, at the same time, off-target methylation must be avoided. However, the underlying mechanisms that ensure this precision remain unknown. Here, we show that SPOCD1 directly interacts with SPIN1, a chromatin reader that primarily binds H3K4me3 and this association is augmented by H3K9me3. The prevailing assumption is that all molecular events required for piRNA-directed DNA methylation occur after the engagement of MIWI2. Interestingly, we find that SPIN1 expression precedes that of both SPOCD1 and MIWI2. Furthermore, we demonstrate that young LINE1s, but not old copies are marked by H3K4me3 and H3K9me3 prior to the initiation of piRNA-directed DNA methylation. We generated a Spocd1 separation-of-function allele in the mouse that encodes a SPOCD1 variant that no longer interacts with SPIN1. We found that the SPOCD1-SPIN1 interaction is essential for spermatogenesis and piRNA-directed DNA methylation of young LINE1 elements. We propose that young LINE1 elements require a two-factor authentication process for DNA methylation, the first being the recruitment of SPIN1-SPOCD1 to licence the locus and the second is MIWI2 engagement with the nascent transcript, which is the trigger for methylation. In summary, independent events that licence, and trigger methylation underpin the basis of precision.
Project description:The PIWI-interacting RNA (piRNA) pathway guides the DNA methylation of young active transposons during male mouse germline development. piRNAs tether the PIWI protein MIWI2 (PIWIL4) to the nascent transposon transcript that results in DNA methylation through SPOCD1. Transposon methylation requires exacting precision: all copies need to be methylated yet, at the same time, off-target methylation must be avoided. However, the underlying mechanisms that ensure this precision remain unknown. Here, we show that SPOCD1 directly interacts with SPIN1 (SPINDLIN1), a chromatin reader that primarily binds H3K4me3 K9me3. The prevailing assumption is that all molecular events required for piRNA-directed DNA methylation occur after the engagement of MIWI2. Interestingly, we find that SPIN1 expression precedes that of both SPOCD1 and MIWI2. Furthermore, we demonstrate that young LINE1s, but not old copies are marked by H3K4me3, H3K9me3 and SPIN1 prior to the initiation of piRNA-directed DNA methylation. We generated a Spocd1 separation-of-function allele in the mouse that encodes a SPOCD1 variant that no longer interacts with SPIN1. We found that the SPOCD1-SPIN1 interaction is essential for spermatogenesis and piRNA-directed DNA methylation of young LINE1 elements. We propose that young LINE1 elements require a two-factor authentication process for DNA methylation, the first being the recruitment of SPIN1-SPOCD1 to licence the locus and the second is MIWI2 engagement with the nascent transcript, which is also the trigger for methylation. In summary, independent events that licence, and trigger methylation underpin the basis of precision.
Project description:The PIWI-interacting RNA (piRNA) pathway guides the DNA methylation of young active transposons during male mouse germline development. piRNAs tether the PIWI protein MIWI2 (PIWIL4) to the nascent transposon transcript that results in DNA methylation through SPOCD1. Transposon methylation requires exacting precision: all copies need to be methylated yet, at the same time, off-target methylation must be avoided. However, the underlying mechanisms that ensure this precision remain unknown. Here, we show that SPOCD1 directly interacts with SPIN1, a chromatin reader that primarily binds H3K4me3 and this association is augmented by H3K9me3. The prevailing assumption is that all molecular events required for piRNA-directed DNA methylation occur after the engagement of MIWI2. Interestingly, we find that SPIN1 expression precedes that of both SPOCD1 and MIWI2. Furthermore, we demonstrate that young LINE1s, but not old copies are marked by H3K4me3 and H3K9me3 prior to the initiation of piRNA-directed DNA methylation. We generated a Spocd1 separation-of-function allele in the mouse that encodes a SPOCD1 variant that no longer interacts with SPIN1. We found that the SPOCD1-SPIN1 interaction is essential for spermatogenesis and piRNA-directed DNA methylation of young LINE1 elements. We propose that young LINE1 elements require a two-factor authentication process for DNA methylation, the first being the recruitment of SPIN1-SPOCD1 to licence the locus and the second is MIWI2 engagement with the nascent transcript, which is the trigger for methylation. In summary, independent events that licence, and trigger methylation underpin the basis of precision.
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.
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.
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.
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.