Unveiling RCOR1 as a rheostat at transcriptionally permissive chromatin

The classical neuronal-gene corepressor RCOR1/CoREST is paradoxically enriched in transcriptionally active chromatin. Here the authors show RCOR1 is recruited during promoter-proximal pausing and negatively regulates the nascent-transcript synthesis. They also show that an RCOR1-LSD1- HDAC1 complex removes lysine acetylation from RNA polymerase II to repress transcription. RCOR1 is a known transcription repressor that recruits and positions LSD1 and HDAC1/2 on chromatin to erase histone methylation and acetylation. However, there is currently an incomplete understanding of RCOR1's range of localization and function. Here, we probe RCOR1's distribution on a genome-wide scale and unexpectedly find that RCOR1 is predominantly associated with transcriptionally active genes. Biochemical analysis reveals that RCOR1 associates with RNA Polymerase II (POL-II) during transcription and deacetylates its carboxy-terminal domain (CTD) at lysine 7. We provide evidence that this non-canonical RCOR1 activity is linked to dampening of POL-II productive elongation at actively transcribing genes. Thus, RCOR1 represses transcription in two ways-first, via a canonical mechanism by erasing transcriptionally permissive histone modifications through associating with HDACs and, second, via a non-canonical mechanism that deacetylates RNA POL-II's CTD to inhibit productive elongation. We conclude that RCOR1 is a transcription rheostat.

Automated summary

RCOR1 is paradoxically enriched in transcriptionally active chromatin and represses transcription through two mechanisms.