Vaillant, I. | bioRxiv Science

bioRxiv2023

Biallelic non-productive enhancer-promoter interaction precedes imprinted expression of Kcnk9 during mouse neural commitment

How constitutive allelic methylation at imprinting control regions (ICRs) interacts with other levels of regulation to drive timely parental allele-specific expression along large imprinted domains remains partially understood. To gain insight into the regulation of the Peg13-Kcnk9 domain, an imprinted domain with important brain functions, during neural commitment, we performed an integrative analysis of the epigenetic, transcriptomic and cis-spatial organisation in an allele-specific manner in a mouse stem cell-based model of corticogenesis that recapitulates the control of imprinted gene expression during neurodevelopment. We evidence that despite an allelic higher-order chromatin structure associated with the paternally CTCF-bound Peg13 ICR, the enhancer-Kcnk9 promoter contacts can occur on both alleles, although they are only productive on the maternal allele. This observation challenges the canonical model in which CTCF binding isolates the enhancer and its target gene on either side, and suggests a more nuanced role for allelic CTCF binding at some ICRs.

molecular biology↗

bioRxiv2018

Differential requirement of MED14 and UVH6 for heterochromatin transcription upon destabilization of silencing

Constitutive heterochromatin is commonly associated with high levels of repressive epigenetic marks and is stably maintained transcriptionally silent by the concerted action of different, yet convergent, silencing pathways. Reactivation of heterochromatin transcription is generally associated with alterations in levels of these epigenetic marks. However, in mutants for particular epigenetic regulators, or upon particular environmental changes such as heat stress, heterochromatin-associated silencing is destabilized without noticeable changes in epigenetic marks. This suggests that transcription can occur in a non-permissive chromatin context, yet the factors involved remain poorly known. Here, we show that heat stress-induced transcription of heterochromatin depends on the TFIIH component UVH6 and the Mediator subunit MED14. Mutants for these two factors exhibit hypersensitivity to heat stress, and under these conditions, UVH6 and MED14 are required for transcription of a high number of loci. We further show that MED14, but not UVH6, is required for transcription when heterochromatin silencing is destabilized in the absence of stress. In this case, MED14 requires proper chromatin patterns of repressive epigenetic marks for its function. We also uncover that MED14 regulates non-CG DNA methylation at a subset of RNA-directed DNA methylation target loci. These findings provide insight into the control of heterochromatin transcription upon silencing destabilization and identify MED14 as a regulator of DNA methylation.

plant biology↗