Biology subjects

Yu, J.-R.

Publications and source records attributed to Yu, J.-R..

3 recordsLinked to original sources

bioRxiv2018

Multiple modes of PRC2 inhibition elicit global chromatin alterations in H3K27M pediatric glioma

A methionine substitution at lysine 27 on histone H3 variants (H3K27M) characterizes ~80% of diffuse intrinsic pontine gliomas (DIPG) and inhibits PRC2 in a dominant negative fashion. Yet, the mechanisms for this inhibition and abnormal epigenomic landscape have not been resolved. Using quantitative proteomics, we discovered that robust PRC2 inhibition requires levels of H3K27M greatly exceeding those of PRC2, seen in DIPG. While PRC2 inhibition requires interaction with H3K27M, we found this interaction on chromatin is transient with PRC2 largely being released from H3K27M. Unexpectedly, inhibition persisted even after PRC2 dissociated from H3K27M-chromatin suggesting a lasting impact on PRC2. Furthermore, allosterically activated PRC2 is particularly sensitive to K27M leading to a failure to spread H3K27me3 at distinct foci. In turn, levels of Polycomb antagonists such as H3K36me2 are elevated suggesting a more global, downstream effect on the epigenome. Together, these findings reveal the conditions required for H3K27M-mediated PRC2 inhibition and reconcile seemingly paradoxical effects of H3K27M on PRC2 recruitment and activity.

molecular biology↗

bioRxiv2018

Automethylation of PRC2 fine-tunes its catalytic activity on chromatin

The catalytic activity of PRC2 is central to maintain transcriptional repression by H3K27me3-decorated facultative heterochromatin in mammalian cells. To date, multiple factors have been reported to regulate PRC2 activity. Here, we demonstrate that PRC2 methylates itself on EZH1/2 and SUZ12 subunits, with EZH1/2-K514 being the major automethylation site in cells. The functional studies of automethylation on EZH2 indicate automethylation as a self-activating mechanism for PRC2 in the absence of stimulatory cofactors like AEBP2. Together, our study reveals PRC2 automethylation as a novel regulatory mechanism of PRC2 activity on chromatin.

biochemistry↗

bioRxiv2017

Allosteric activation dictates PRC2 activity independent of its recruitment to chromatin

PRC2 is a therapeutic target for several types of cancers currently undergoing clinical trials. Its activity is regulated by a positive feedback loop whereby its terminal enzymatic product, H3K27me3, is specifically recognized and bound by an aromatic cage present in its EED subunit. The ensuing allosteric activation of the complex stimulates H3K27me3 deposition on chromatin. Here, we report a step-wise feedback mechanism entailing key residues within distinctive interfacing motifs of EZH2 or EED that are found mutated in cancers and/or Weaver syndrome. PRC2 harboring these EZH2 or EED mutants manifest little activity in vivo but, unexpectedly, exhibited similar chromatin association as wild-type PRC2, indicating an uncoupling of PRC2 activity and recruitment. With genetic and chemical tools, we further demonstrated that targeting allosteric activation overrode the gain-of-function effect of EZH2Y646X oncogenic mutations. These results revealed critical implications to the regulation and biology of PRC2 and a novel vulnerability in tackling PRC2-addicted cancers.

biochemistry↗