Dynamic Polycomb-CBC crosstalk orchestrates mRNA production at transcriptionally active loci in plants [RIP-seq]

Active histone modifications and efficient cotranscriptional mRNA processing act in concert to promote transcription, whereas repressive histone marks are normally depleted from active genes. However, the localization of repressive histone marks at transcribing genes and the regulatory mechanism in mRNA transcription are largely unclear.

Here, we show that in Arabidopsis thaliana, the chromodomain (CD) H3K27me3 reader LIKE HETEROCHROMATIN PROTEIN1 (LHP1) binds nascent precursor mRNA (pre-mRNA) through its middle intrinsically disordered region (IDR) at H3K27me3-coated chromatin loci, thereby attenuating transcription efficiency. This interaction is subsequently disrupted by mRNA cap-binding complex (CBC) to complete transcription. We illustrate how this interplay fine-tunes WUSCHEL (WUS) transcription in shoot apical meristem region to maintain stem cell homeostasis.