Intergenic Polycomb target sites are dynamically marked by non-coding transcription during lineage commitment

Area of Science:

• Epigenetics
• Molecular Biology
• Developmental Biology

Background:

• Non-coding RNAs (ncRNAs) play roles in Polycomb protein recruitment and gene activation.
• The dynamic interplay between ncRNA transcription and Polycomb group (PcG) protein recruitment during differentiation is not fully understood.

Purpose of the Study:

• To investigate dynamic changes in the relationship between ncRNA transcription and PcG protein recruitment during differentiation.
• To identify and characterize novel PcG-recruiting elements.

Main Methods:

• Profiling of purified cell populations during murine in vitro neural differentiation.
• Reporter assays to assess gene repression by transcribed TIP sites.
• Knockdown experiments to determine the functional role of TIP ncRNAs.

Main Results:

• Over 50% of regulated intergenic non-coding transcripts correspond to PcG target sites, designated Transcribed Intergenic Polycomb (TIP) sites.
• The relationship between TIP transcription and PcG recruitment dynamically switches during differentiation, with states of mutual exclusion or co-occurrence.
• Transcribed TIP sites can repress flanking genes, and TIP ncRNAs are required for gene repression in cis and trans.

Conclusions:

• TIP transcription ensures coordinated gene network regulation through dynamic switching and PcG protein recruitment during lineage commitment.
• TIP sites represent a novel class of regulatory elements involved in epigenetic control during development.