Jung, I. | Search bioRxiv

bioRxiv2017

Histone H3 Lysine 4 methyltransferases MLL3 and MLL4 Modulate Long-range Chromatin Interactions at Enhancers

Regulation of gene expression in mammalian cells depends on long-range chromatin interactions between enhancers and promoters. Currently, the exact mechanisms that connect distal enhancers to their specific target promoters remain to be fully elucidated. Here we show that the histone H3 Lysine 4 monomethylation (H3K4me1) writer proteins MLL3 and MLL4 (MLL3/4) play an active role in this process. We demonstrate that in differentiating mouse embryonic stem cells, MLL3/4-dependent deposition of H3K4me1 at enhancers correlates with increased levels of chromatin interactions, whereas loss of MLL3/4 leads to greatly reduced frequencies of chromatin interactions and failure of lineage-specific gene expression programs. We further show that H3K4me1 facilitates recruitment of the Cohesin complex to chromatin in vitro and in vivo, providing a potential mechanism for MLL3/4 to promote chromatin looping. Taken together, our results support an active role for MLL3/4 in modulating chromatin organization at enhancers in mammalian cells.

genomics↗

bioRxiv2016

The human functional genome defined by genetic diversity

Large scale efforts to sequence whole human genomes provide extensive data on the non-coding portion of the genome. We used variation information from 11,257 human genomes to describe the spectrum of sequence conservation in the population. We established the genome-wide variability for each nucleotide in the context of the surrounding sequence in order to identify departure from expectation at the population level (context-dependent conservation). We characterized the population diversity for functional elements in the genome and identified the coordination of conserved sequences of distal and cis enhancers, chromatin marks, promoters, coding and intronic regions. The most context-dependent conserved regions of the genome are associated with unique functional annotations and a genomic organization that spreads up to one megabase. Importantly, these regions are enriched by over 100-fold of non-coding pathogenic variants. This analysis of human genetic diversity thus provides a detailed view of sequence conservation, functional constraint and genomic organization of the human genome. Specifically, it identifies highly conserved non-coding sequences that are not captured by analysis of interspecies conservation and are greatly enriched in disease variants.

genomics↗