title: Functions of BET proteins in erythroid gene expression.
abstract: Inhibitors of bromodomain and extraterminal motif proteins (BETs) are being evaluated for the treatment of cancer and other diseases, yet much remains to be learned about how BET proteins function during normal physiology. We used genomic and genetic approaches to examine BET function in a hematopoietic maturation system driven by GATA1, an acetylated transcription factor previously shown to interact with BETs. We found that BRD2, BRD3, and BRD4 were variably recruited to GATA1-regulated genes, with BRD3 binding the greatest number of GATA1-occupied sites. Pharmacologic BET inhibition impaired GATA1-mediated transcriptional activation, but not repression, genome-wide. Mechanistically, BETs promoted chromatin occupancy of GATA1 and subsequently supported transcriptional activation. Using a combination of CRISPR-Cas9-mediated genomic engineering and shRNA approaches, we observed that depletion of either BRD2 or BRD4 alone blunted erythroid gene activation. Surprisingly, depletion of BRD3 only affected erythroid transcription in the context of BRD2 deficiency. Consistent with functional overlap among BET proteins, forced BRD3 expression substantially rescued defects caused by BRD2 deficiency. These results suggest that pharmacologic BET inhibition should be interpreted in the context of distinct steps in transcriptional activation and overlapping functions among BET family members.
authors.affiliation: Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA; Perelman School of Medicine, University of Pennsylvania, Philadelphia PA; and.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Stonestrom
authors.affiliation: Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA; Perelman School of Medicine, University of Pennsylvania, Philadelphia PA; and.
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Hsu
authors.affiliation: Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA;
authors.forename: Kristen S
authors.initials: KS
authors.lastname: Jahn
authors.affiliation: Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA;
authors.forename: Peng
authors.initials: P
authors.lastname: Huang
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA.
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Keller
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA.
authors.forename: Belinda M
authors.initials: BM
authors.lastname: Giardine
authors.affiliation: Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA; Perelman School of Medicine, University of Pennsylvania, Philadelphia PA; and.
authors.forename: Stephan
authors.initials: S
authors.lastname: Kadauke
authors.affiliation: Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA; Perelman School of Medicine, University of Pennsylvania, Philadelphia PA; and.
authors.forename: Amy E
authors.initials: AE
authors.lastname: Campbell
authors.affiliation: Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA;
authors.forename: Perry
authors.initials: P
authors.lastname: Evans
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA.
authors.forename: Ross C
authors.initials: RC
authors.lastname: Hardison
authors.affiliation: Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA; Perelman School of Medicine, University of Pennsylvania, Philadelphia PA; and.
authors.forename: Gerd A
authors.initials: GA
authors.lastname: Blobel
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D041905:Erythroid Cells / Q000378:metabolism*; D050982:GATA1 Transcription Factor / Q000235:genetics; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D006410:Hematopoiesis / Q000235:genetics*; D006801:Humans; D051379:Mice; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000502:physiology*; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000502:physiology*
chemical_list: D050982:GATA1 Transcription Factor; D016601:RNA-Binding Proteins; D017346:Protein Serine-Threonine Kinases