Characterization of Drosophila melanogaster JmjC+N histone demethylases

In this article, we characterize histone demethylase activity of the entire family of JmjC+N proteins of Drosophila melanogaster. Our results show that Lid (little imaginal discs), which is structurally homologous to JARID1, demethylates H3K4me3. However, contrary to what would be inferred from its demethylase activity, lid contributes to the establishment of transcriptionally competent chromatin states as: (i) is required for histone H3 acetylation; (ii) contributes to expression of the homoeotic gene Ultrabithorax (Ubx); and (iii) antagonizes heterochromatin-mediated gene silencing (PEV). These results, which are consistent with the identification of lid as a trithorax group (trxG) gene, are discussed in the context of current models for the contribution of H3K4me3 to the regulation of gene expression. Here, we also show that the two Drosophila JMJD2 homologues, dJMJD2(1)/CG15835 and dJMJD2(2)/CG33182, are capable of demethylating both H3K9me3 and H3K36me3. dJMJD2(1)/CG15835 regulates heterochromatin organization, as its over-expression induces spreading of HP1, out of heterochromatin, into euchromatin, without affecting the actual pattern of histone modifications of heterochromatin. dJMJD2(1)/CG15835 is excluded from heterochromatin and localizes to multiple euchromatic sites, where it regulates H3K36 methylation. These results indicate that dJMJD2(1)/CG15835 contributes to delimit hetero- and euchromatic territories through the regulation of H3K36 methylation in euchromatin. On the other hand, dJARID2/CG3654 shows no demethylase activity on H3K4me3, H3K9me3, H3K27me3, H3K36me3 and H4K20me3

Functional analysis of JmjC+N histone demethylases in Drosophila melanogaster

La metilació de les lisines de les histones està implicada en les funcions associades a la cromatina, com l’expressió gènica o la formació d’heterocromatina. És una modificació covalent afegida per metiltransferases d’histones i eliminada per desmetilases d’histones, que han estat descobertes recentment. Hem caracteritzat els grups de desmetilases que contenen dominis Jumonji C i Jumonji N a l’organisme model Drosophila melanogaster. Observem que les dues dKDM4 actuen sobre H3K36me3 i H3K9me3 i que LID/dKDM5 desmetila H3K4me3. La distribució d’HP1a es veu afectada per la sobreexpressió de dKDM4A. A més, hem analitzat la localització de LID/dKDM5 als discos imaginals d’ala i quins efectes té LID sobre l’expressió gènica i la trimetilació de H3K4 en aquest teixit. Hem observat que LID es troba als llocs d’inici de la transcripció de gens actius relacionats amb diferenciació i desenvolupament. Els gens diana de LID contenen H3K4me3 i H3K36me3 i RNAPII fosforilada a la serina 5 i a la serina 2. Una disminució de lid provoca una lleu baixada en l’expressió dels seus gens diana, la qual cosa suggereix que la desmetilasa té un paper en l’ajust dels nivells d’expressió.Histone lysine methylation is involved in chromatin related cell functions, such as gene expression or heterochromatin formation. It is a covalent modification added by histone methyltransferases and removed by histone demethylases, discovered in the recent years. We characterized the groups of demethylases that contain both Jumonji C and Jumonji N domains in the model organism 2 Drosophila melanogaster. We show that dKDM4s act on H3K36me3 and H3K9me3 and LID/dKDM5 targets H3K4me3. HP1a distribution is affected by dKDM4A overexpression. In addition, we analyzed LID/dKDM5 localization in wing imaginal discs and how LID affects gene expression and trimethylation of H3K4 in this tissue. We observed that LID localizes at the transcription start sites of active genes related to development and differentiation. LID target genes contain H3K4me3 and H3K36me3 and RNAPII, phosphorylated at serine 5 and serine 2. Downregulation of lid produces a weak decrease in the expression of LID targets, suggesting a role of the demethylase in fine-tuning expression levels

dKDM5/LID regulates H3K4me3 dynamics at the transcription-start site (TSS) of actively transcribed developmental genes

H3K4me3 is a histone modification that accumulates at the transcription-start site (TSS) of active genes and is known to be important for transcription activation. The way in which H3K4me3 is regulated at TSS and the actual molecular basis of its contribution to transcription remain largely unanswered. To address these questions, we have analyzed the contribution of dKDM5/LID, the main H3K4me3 demethylase in Drosophila, to the regulation of the pattern of H3K4me3. ChIP-seq results show that, at developmental genes, dKDM5/LID localizes at TSS and regulates H3K4me3. dKDM5/LID target genes are highly transcribed and enriched in active RNApol II and H3K36me3, suggesting a positive contribution to transcription. Expression-profiling show that, though weakly, dKDM5/LID target genes are significantly downregulated upon dKDM5/LID depletion. Furthermore, dKDM5/LID depletion results in decreased RNApol II occupancy, particularly by the promoter-proximal Pol lloser5 form. Our results also show that ASH2, an evolutionarily conserved factor that locates at TSS and is required for H3K4me3, binds and positively regulates dKDM5/LID target genes. However, dKDM5/LID and ASH2 do not bind simultaneously and recognize different chromatin states, enriched in H3K4me3 and not, respectively. These results indicate that, at developmental genes, dKDM5/LID and ASH2 coordinately regulate H3K4me3 at TSS and that this dynamic regulation contributes to transcription

dKDM5/LID regulates H3K4me3 dynamics at the transcription-start site (TSS) of actively transcribed developmental genes

H3K4me3 is a histone modification that accumulates at the transcription-start site (TSS) of active genes and is known to be important for transcription activation. The way in which H3K4me3 is regulated at TSS and the actual molecular basis of its contribution to transcription remain largely unanswered. To address these questions, we have analyzed the contribution of dKDM5/LID, the main H3K4me3 demethylase in Drosophila, to the regulation of the pattern of H3K4me3. ChIP-seq results show that, at developmental genes, dKDM5/LID localizes at TSS and regulates H3K4me3. dKDM5/LID target genes are highly transcribed and enriched in active RNApol II and H3K36me3, suggesting a positive contribution to transcription. Expression-profiling show that, though weakly, dKDM5/LID target genes are significantly downregulated upon dKDM5/LID depletion. Furthermore, dKDM5/LID depletion results in decreased RNApol II occupancy, particularly by the promoter-proximal Pol lloser5 form. Our results also show that ASH2, an evolutionarily conserved factor that locates at TSS and is required for H3K4me3, binds and positively regulates dKDM5/LID target genes. However, dKDM5/LID and ASH2 do not bind simultaneously and recognize different chromatin states, enriched in H3K4me3 and not, respectively. These results indicate that, at developmental genes, dKDM5/LID and ASH2 coordinately regulate H3K4me3 at TSS and that this dynamic regulation contributes to transcription