Loss of Su(var)3-9 and SetDB1 disrupts late stages of larval development of Drosophila
Ontology highlight
ABSTRACT: Methylation of H3K9 histone residue is a marker of gene silencing in eukaryotes. Three enzymes responsible for adding this modification – G9a, SetDB1/Egg, and Su(var)3-9 – are known in Drosophila. To understand how simultaneous mutations of SetDB1 and Su(var)3-9, or all three proteins may affect the fly development, appropriate combinations were obtained. Double mutants egg; Su(var)3-9 displayed pronounced embryonic lethality, slower larval growth and died before or during metamorphosis. Analysis of transcription in larval salivary glands and wing imaginal disks indicated that the effect of double mutation is tissue-specific. In salivary gland chromosomes, affected genes display low H3K9me2 enrichment and are rarely bound by SetDB1 or Su(var)3-9. We suppose that each of these enzymes directly or indirectly controls its own set of gene targets in different organs, and double mutation results in an imbalanced developmental program. This also indicates that SetDB1 and Su(var)3-9 may affect transcription via H3K9-independent mechanisms. Unexpectedly, in double and triple mutants, amount of di-and tri-methylated H3K9 is drastically reduced, but not completely absent. We hypothesize that this residual methylation implies the existence of additional H3K9-specific methyltransferase in Drosophila.
Project description:Histone modifications are a class of epigenetic marks with prominent roles in gene regulation in eukaryotes. One such mark, predominantly inactivation-related, is methylation of histone H3 lysine 9 (H3K9). In the present study, we decipher the interplay between two evolutionary conserved Drosophila H3K9-specific histone methyltransferases, SU(VAR)3-9 and SETDB1. We asked whether SETDB1 is required for targeting of SU(VAR)3-9. Using DamID-seq, we obtained SU(VAR)3-9 binding profiles for the chromosomes from larval salivary glands and germline cells from adult females, and compared profiles between the wild type and SETDB1-mutant backgrounds. Our analyses indicate that the vast majority of single-copy genes in euchromatin are targeted by SU(VAR)3-9 only in the presence of SETDB1, whereas repeated sequences in heterochromatin is largely SETDB1-independent. Interestingly, piRNA clusters 42AB and 38C behave differently in terms of SU(VAR)3-9 binding in somatic and germline cells. Namely, SU(VAR)3-9 binding to these piRNA clusters is independent of SETDB1 in somatic cells, whereas it is SETDB1-dependent in the germline. In addition, we compared SU(VAR)3-9 profiles in female germline cells at different developmental stages (whole juvenile ovaries and mature nurse cells). It turned out that SU(VAR)3-9 binding is influenced both by the presence of SETDB1, as well as by the differentiation stage.
Project description:H3K9 methylation is a mark of inactive chromatin. In D.melanogaster, three enzymes (SU(VAR)3-9, EGG, and dG9A) are responsible for creating the H3K9 methyl mark. We have investigated the effects of loss of SU(VAR)3-9 and EGG on gene expression in adult heads using microarray analysis. Keywords: Expression profiling by microarray
Project description:Three distinct enzymes are known to be capable of methylating lysine 9 residue of the histone H3 in Drosophila melanogaster: Su(var)3-9, SetDB1, and G9a. Here, we explored functional specialization of the two of them: SetDB1 and Su(var)3-9. Using DamID approach, we generated the binding profile for SetDB1 in salivary gland chromosomes, and matched it to the previously published profile of Su(var)3-9. Unlike Su(var)3-9, SetDB1 is an euchromatic protein that is absent from repeated DNA compartment, and is largely restricted to TSSes and 5'UTRs of moderately active ubiquitously expressed genes. Significant SetDB1 association is also observed at or near insulator protein CP190 binding sites. Extensive, yet not exact colocalization SetDB1 with Su(var)3-9 occurs only along the chromosome 4. Importantly, SetDB1 and H3K9me2/3-enriched sites tend to display poor overlap. At the same time, SetDB1 has clear connection with the distribution of H3K27me3 mark. SetDB1 binds outside the domains possessing this modification, and about half of the borders of H3K27me3 domains are decorated by SetDB1 binding sites together with actively transcribed genes. Given that SetDB1 displays low correlation with H3K9 methylation and binds to the TSSes of active genes, that are usually nucleosome-poor, we speculate that in somatic cells, SetDB1 may contribute to the methylation of a broader set of chromosomal proteins than just H3K9. In addition, via association with insulator proteins and transcription machinery, SetDB1 can be expected to play a role in the establishment of chromatin functional domains.
Project description:Three distinct enzymes are known to be capable of methylating lysine 9 residue of the histone H3 in Drosophila melanogaster: Su(var)3-9, SetDB1, and G9a. Here, we explored functional specialization of the two of them: SetDB1 and Su(var)3-9. Using DamID approach, we generated the binding profile for SetDB1 in salivary gland chromosomes, and matched it to the previously published profile of Su(var)3-9. Unlike Su(var)3-9, SetDB1 is an euchromatic protein that is absent from repeated DNA compartment, and is largely restricted to TSSes and 5'UTRs of moderately active ubiquitously expressed genes. Significant SetDB1 association is also observed at or near insulator protein CP190 binding sites. Extensive, yet not exact colocalization SetDB1 with Su(var)3-9 occurs only along the chromosome 4. Importantly, SetDB1 and H3K9me2/3-enriched sites tend to display poor overlap. At the same time, SetDB1 has clear connection with the distribution of H3K27me3 mark. SetDB1 binds outside the domains possessing this modification, and about half of the borders of H3K27me3 domains are decorated by SetDB1 binding sites together with actively transcribed genes. Given that SetDB1 displays low correlation with H3K9 methylation and binds to the TSSes of active genes, that are usually nucleosome-poor, we speculate that in somatic cells, SetDB1 may contribute to the methylation of a broader set of chromosomal proteins than just H3K9. In addition, via association with insulator proteins and transcription machinery, SetDB1 can be expected to play a role in the establishment of chromatin functional domains.
Project description:Heterochromatin protein 1a (HP1a) is a chromatin associated protein that has been well studied in many model organisms, such as Drosophila, where it is a determining factor for classical heterochromatin. HP1a is associated with the two histone methyltransferases SETDB1 and Su(var)3-9, which mediate H3K9 methylation marks and participate in the establishment and spreading of HP1a enriched chromatin. While HP1a is generally regarded as a factor that represses gene transcription, several reports have linked HP1a binding to active genes, and in some cases, it has been shown to stimulate transcriptional activity. To clarify the function of HP1a in transcription regulation and its association with Su(var)3-9, SETDB1 and the chromosome 4 specific protein POF, we conducted genome-wide expression studies and combined the results with available binding data in Drosophila melanogaster. The results suggested that HP1a has a repressing function on chromosome 4, where it preferentially targets non-ubiquitously expressed genes (NUEGs), and a stimulating function in pericentromeric regions. Further, we showed that the effects of SETDB1 and Su(var)3-9 are similar to HP1a, and on chromosome 4, Su(var)3-9, SETDB1 and HP1a target the same genes. In contrast, transposons are repressed by HP1a and Su(var)3-9 but are un-affected by SETDB1 and POF. In addition, we found that the binding level and expression effects of HP1a are affected by gene length. Our results indicate that genes have adapted to be properly expressed in their local chromatin environment. We prepared total RNA from 1st instar larvae trans-heterozygous for HP1a04/HP1a05, trans-heterozygous Su(var)3-9evo/Su(var)3-906, homozygous Setdb110.1/ Setdb110.1 mutants and trans-heterozygous HP1a04 PofD119/HP1a05 PofD119 double mutants three biological replicates, as well as from six biological replicates of wildtype control 1st instar larvae.
Project description:In eukaryotes, trimethylation of lysine 9 on histone H3 (H3K9) is associated with transcriptional silencing of transposable elements (TEs). In drosophila ovaries, this heterochromatic repressive mark is thought to be deposited by SetDB1 on TE genomic loci after the initial recognition of nascent transcripts by PIWI-interacting RNAs (piRNAs) loaded on the Piwi protein. Here, we show that the nucleosome remodeler Mi-2, in complex with its partner MEP-1, forms a subunit that is transiently associated, in a MEP-1 C-terminus-dependent manner, with known Piwi interactors, including a recently reported SUMO ligase Su(var)2-10. Together with the histone deacetylase Rpd3, this module is involved in the piRNA-dependent TE silencing, correlated with H3K9 deacetylation and trimethylation. Therefore. drosophila piRNA-mediated transcriptional silencing involves three epigenetic effectors, a remodeler, Mi-2, an eraser, Rpd3 and a writer, SetDB1, in addition to the Su(var)2-10 SUMO ligase.
Project description:Heterochromatin protein 1a (HP1a) is a chromatin associated protein that has been well studied in many model organisms, such as Drosophila, where it is a determining factor for classical heterochromatin. HP1a is associated with the two histone methyltransferases SETDB1 and Su(var)3-9, which mediate H3K9 methylation marks and participate in the establishment and spreading of HP1a enriched chromatin. While HP1a is generally regarded as a factor that represses gene transcription, several reports have linked HP1a binding to active genes, and in some cases, it has been shown to stimulate transcriptional activity. To clarify the function of HP1a in transcription regulation and its association with Su(var)3-9, SETDB1 and the chromosome 4 specific protein POF, we conducted genome-wide expression studies and combined the results with available binding data in Drosophila melanogaster. The results suggested that HP1a has a repressing function on chromosome 4, where it preferentially targets non-ubiquitously expressed genes (NUEGs), and a stimulating function in pericentromeric regions. Further, we showed that the effects of SETDB1 and Su(var)3-9 are similar to HP1a, and on chromosome 4, Su(var)3-9, SETDB1 and HP1a target the same genes. In contrast, transposons are repressed by HP1a and Su(var)3-9 but are un-affected by SETDB1 and POF. In addition, we found that the binding level and expression effects of HP1a are affected by gene length. Our results indicate that genes have adapted to be properly expressed in their local chromatin environment.
Project description:In Drosophila, Piwi-induced transcriptional repression is associated with the establishment of repressive chromatin marks by the histone methyltrasferase SetDB1, however how the Piwi/piRNA complex recruits this effector to chromatin targets is poorly understood. We identified a new player in piRNA-guided transcriptional silencing encoded by the Su(var)2-10 gene. Su(var)2-10 is required for transcriptional silencing and deposition of repressive chromatin marks on transposons and it physically associates with the Piwi/piRNA target recognition complex. Recruitment of Su(var)2-10 to a target locus in a piRNA-independent fashion induces transcriptional repression and deposition of the H3K9 trimethyl mark by the histone methyltransferase dSetDB1/Eggless. Su(var)2-10 belongs to a conserved family of proteins that function as SUMO E3 ligases and we found that the SUMO pathway is essential for the repressive function of Su(var)2-10 and for transcriptional repression of transposons. Together, our data identifies Su(var)2-10 as an essential component of the piRNA-induced transcriptional silencing pathway that links the target recognition complex to the silencing effector and reveals a novel role of SUMO modification in the piRNA-induced repression.
Project description:In eukaryotes, trimethylation of lysine 9 on histone H3 (H3K9) is associated with transcriptional silencing of transposable elements (TEs). In drosophila ovaries, this heterochromatic repressive mark is thought to be deposited by SetDB1 on TE genomic loci after the initial recognition of nascent transcripts by PIWI-interacting RNAs (piRNAs) loaded on the Piwi protein. Here, we show that the nucleosome remodeler Mi-2, in complex with its partner MEP-1, forms a subunit that is transiently associated, in a MEP-1 C-terminus-dependent manner, with known Piwi interactors, including a recently reported SUMO ligase Su(var)2-10. Together with the histone deacetylase Rpd3, this module is involved in the piRNA-dependent TE silencing, correlated with H3K9 deacetylation and trimethylation. Therefore. drosophila piRNA-mediated transcriptional silencing involves three epigenetic effectors, a remodeler, Mi-2, an eraser, Rpd3 and a writer, SetDB1, in addition to the Su(var)2-10 SUMO ligase.
Project description:Heterochromatin protein 1 (HP1) proteins are important regulators of heterochromatin mediated gene silencing and chromosome structure and it is well known as the reader of the heterochromatin mark methylation of histone H3 lysine 9 (H3K9me). In Drosophila three different histone lysine methyl transferases (HKMTs) are associated with the methylation of H3K9; Su(var)3-9, Setdb1 and G9a. To gain insights on the dependence of HP1a on the three different HKMTs, the division of labor between these methyl transferases and the dependence of HP1a on H3K9me we have studied HP1a binding in relation to H3K9me in mutants of these HKMTs. We show that Su(var)3-9 is responsible for the HP1a H3K9me-dependent binding in pericentromeric regions while Setdb1 controls the HP1a H3K9me-dependent binding to cytological region 2L:31 and together with POF chromosome 4. HP1a binds to the promoters and within gene bodies of active genes in these three regions. More importantly, HP1a bound at promoters of active genes are independent of H3K9me and POF and is associated to heterochromatin protein 2 (HP2) and open chromatin. Our results supports a model where HP1a nucleates with high affinity independent of H3K9me in promoters of active genes and then spreads via H3K9 methylation and transient looping contacts with those H3K9me target sites. In total 44 samples; 2 replicates for each genotype and for each ChIP (HP1a, H3K9me2 and H3K9me3)