BioProject

Transcription of genes residing within constitutive heterochromatin is paradoxical to the tenets of epigenetic code. More...

Transcription of genes residing within constitutive heterochromatin is paradoxical to the tenets of epigenetic code. Regulatory mechanisms of Drosophila melanogaster heterochromatic gene transcription remain largely unknown. We investigated the contribution of pericentromeric genome organization and heterochromatic factors in orchestrating heterochromatic gene expression. Using 5C-seq, we characterized the pericentromeric TADs in Drosophila melanogaster. Het TAD borders are enriched in nuclear matrix attachment regions while the intra-TAD interactions are mediated by various insulator binding proteins. Heterochromatic genes of similar expression levels cluster into Het TADs, indicating transcriptional co-regulation. HP1a or Su(var)3-9 RNAi results in perturbation of global pericentromeric TAD organization but the expression of the heterochromatic genes is minimally affected. A subset of active heterochromatic genes has been shown to have combination of HP1a/H3K9me3 with H3K36me3 at their exons. Consequently, knock-down of dMES-4 (H3K36 methyl transferase) downregulates expression of the heterochromatic genes. Furthermore, dADD1, present near the TSS of the active heterochromatic genes, is likely to regulate the heterochromatic gene expression in the presence of HP1a or H3K9me3 marks. Therefore, our findings provide mechanistic insights into the interplay of chromatin interactions and the combination of heterochromatic factors (HP1a, H3K9me3, dMES-4 and dADD1) in regulating heterochromatic gene expression. Overall design: 5C analysis of pericentromeric heterochromatin in untreated and RNAi knockdown of HP1a and Su(Var)3-9 in Drosophila S2 cells. Less...