MORC and MOM1 spatially constrain RNA Polymerase V chromatin positioning to shape DNA methylation landscapes
Plant-specific RNA Polymerase V (Pol V) transcribes noncoding RNAs in the RNA-directed DNA methylation pathway, thereby influencing gene expression and genome stability by controlling de novo DNA methylation. However, the mechanisms governing precise chromatin localization and transcriptional activities of Pol V remain elusive. Here we show that Pol V localization is spatially constrained by the…
RNA Polymerase V (Pol V), a plant-specific enzyme, plays a crucial role in transcribing noncoding RNAs within the RNA-directed DNA methylation pathway. This process influences gene expression and genome stability by regulating de novo DNA methylation. Nonetheless, the precise mechanisms controlling Pol V chromatin localization and its transcriptional activities have remained unclear.
In a recent study, researchers discovered that Pol V localization is spatially constrained by two chromatin regulators: microrchidia (MORC) and MORPHEUS MOLECULE 1 (MOM1). Both MORC and MOM1 facilitate Pol V occupancy at sites near active chromatin. Conversely, the absence of these regulators causes Pol V to redistribute into CMT3-enriched heterochromatin, resulting in noncoding RNA transcription, small RNA production, and DNA methylation.
The researchers propose a combinatorial model in which recruitment, spatial constraint, and DNA methylation feedback work together to define Pol V chromatin distribution and its epigenetic functions. These findings shed light on the intricate mechanisms governing Pol V's role in regulating DNA methylation landscapes in plants.
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