A non-canonical BRD9-containing BAF chromatin remodeling complex regulates naïve pluripotency in mouse embryonic stem cells

ABSTRACT: The mammalian BRG1-associated factors (BAF) complex is a multi-subunit chromatin remodeling complex that is an important component of the embryonic stem cell (ESC) transcriptional regulatory network. However, the role of individual subunits in BAF complex targeting and function needs to be elucidated. Here, we find that the Bromodomain containing protein 9 (BRD9) defines a smaller, non-canonical BAF complex in mouse ESCs that is distinct from the canonical embryonic stem cell BAF (esBAF) and the polybromo-associated BAF (PBAF) complexes. This BRD9-containing BAF complex, or BBAF complex, uniquely incorporates the BRD4-interacting chromatin remodeling associated protein-like (BICRAL) or its paralog BICRA and lacks several esBAF subunits including BAF47, ARID1A and BAF57. We demonstrate that BBAF and esBAF complexes are targeted to different features of the genome and are co-bound with different sets of pluripotency transcription factors. Specifically, BBAF complexes co-localize with key regulators of naïve pluripotency, KLF4 and Sp5, on the genome. Consistent with this, we provide evidence that BBAF’s specific function is to regulate the transcription of genes involved in the maintenance of naïve pluripotency, including Nanog and Prdm14. Additionally, we show that BRD9 is displaced from chromatin by the selective BRD9 bromodomain inhibitor, I-BRD9, and that this leads to changes in target gene expression. Together, our results provide evidence for the identification of a new BAF complex, and demonstrate functionally specific roles for BAF complex assemblies in maintaining the transcriptional network of pluripotency.

INSTRUMENT(S): Orbitrap Fusion

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Embryonic Stem Cell

DISEASE(S): Disease Free

SUBMITTER: James Moresco  

LAB HEAD: Diana C Hargreaves

PROVIDER: PXD010670 | Pride | 2018-10-18

REPOSITORIES: Pride