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Mol Cell. 2017 Oct 19;68(2):398-413.e6. doi: 10.1016/j.molcel.2017.09.016. Epub 2017 Oct 12.

The Elongation Factor Spt6 Maintains ESC Pluripotency by Controlling Super-Enhancers and Counteracting Polycomb Proteins.

Author information

1
Laboratory of Muscle Stem Cells and Gene Regulation, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), NIH, Bethesda, MD 20829, USA.
2
High-Throughput Sequencing Unit, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), NIH, Bethesda, MD 20829, USA.
3
Laboratory of Muscle Stem Cells and Gene Regulation, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), NIH, Bethesda, MD 20829, USA. Electronic address: sartorev@mail.nih.gov.

Abstract

Spt6 coordinates nucleosome dis- and re-assembly, transcriptional elongation, and mRNA processing. Here, we report that depleting Spt6 in embryonic stem cells (ESCs) reduced expression of pluripotency factors, increased expression of cell-lineage-affiliated developmental regulators, and induced cell morphological and biochemical changes indicative of ESC differentiation. Selective downregulation of pluripotency factors upon Spt6 depletion may be mechanistically explained by its enrichment at ESC super-enhancers, where Spt6 controls histone H3K27 acetylation and methylation and super-enhancer RNA transcription. In ESCs, Spt6 interacted with the PRC2 core subunit Suz12 and prevented H3K27me3 accumulation at ESC super-enhancers and associated promoters. Biochemical as well as functional experiments revealed that Spt6 could compete for binding of the PRC2 methyltransferase Ezh2 to Suz12 and reduce PRC2 chromatin engagement. Thus, in addition to serving as a histone chaperone and transcription elongation factor, Spt6 counteracts repression by opposing H3K27me3 deposition at critical genomic regulatory regions.

KEYWORDS:

Spt6; embryonic stem cells; polycomb proteins; super-enhancers

PMID:
29033324
PMCID:
PMC5659763
DOI:
10.1016/j.molcel.2017.09.016
[Indexed for MEDLINE]
Free PMC Article

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