Biology subjects

Singer, D. S.

Publications and source records attributed to Singer, D. S..

4 recordsLinked to original sources

bioRxiv2024

BRD4 expression in microglia supports recruitment of T cells into the CNS and exacerbates EAE

In EAE, a mouse model of multiple sclerosis, immunization with MOG autoantigen results in the generation of Th1/Th17 T cells in the periphery. MOG-specific T cells then invade into the central nervous system (CNS), resulting in neuronal demyelination. Microglia, innate immune cells in the CNS are known to regulate various neuronal diseases. However, the role of microglia in EAE has remained elusive. BRD4 is a BET protein expressed in microglia, whether BRD4 in microglia contributes to EAE has not been determined. We show that EAE pathology was markedly reduced with microglia-specific Brd4 conditional knockout (cKO). In these mice, microglia- T cell interactions were greatly reduced, leading to the lack of T cell reactivation. Microglia specific transcriptome data showed downregulation of genes required for interaction with and reactivation of T cells in Brd4 cKO samples. In summary, BRD4 plays a critical role in regulating microglia function in normal and EAE CNS. SummaryThis study demonstrates that in a EAE model, microglia-specific Brd4 conditional knockout mice were defective in expressing genes required for microglia- T cells interaction and those involved in neuroinflammation, and demyelination resulting in fewer CNS T cell invasion and display marked reduction in EAE pathology.

neuroscience↗

bioRxiv2024

The ESCRT protein CHMP5 promotes T cell leukemia by controlling BRD4-p300-dependent transcription

Oncogene activity rewires cellular transcription, creating new transcription networks to which cancer cells become addicted, by mechanisms that are still poorly understood. Using human and mouse models of T cell acute lymphoblastic leukemia (T-ALL), we identify an essential nuclear role for CHMP5, a cytoplasmic endosomal sorting complex required for transport (ESCRT) protein, in establishing and maintaining the T-ALL transcriptional program. Nuclear CHMP5 promoted the T-ALL gene program by augmenting recruitment of the co-activator BRD4 by the histone acetyl transferase p300 selectively at enhancers and super-enhancers, an interaction that potentiated H3K27 acetylation at these regulatory enhancers. Consequently, loss of CHMP5 diminished BRD4 occupancy at enhancers and super-enhancers and impaired RNA polymerase II pause release, which resulted in downregulation of key T-ALL genes, notably MYC. Reinforcing its importance in T-ALL pathogenesis, CHMP5 deficiency mitigated chemoresistance in human T-ALL cells and abrogated T-ALL induction by oncogenic NOTCH1 in vivo. Thus, the ESCRT protein CHMP5 is an essential positive regulator of the transcriptional machinery promoting T-ALL disease. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/577409v1_ufig1.gif" ALT="Figure 1"> View larger version (59K): org.highwire.dtl.DTLVardef@191e10dorg.highwire.dtl.DTLVardef@4e5093org.highwire.dtl.DTLVardef@18c0a08org.highwire.dtl.DTLVardef@e6a887_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIIdentification of a nuclear role for the cytosolic ESCRT protein CHMP5 in transcription C_LIO_LICHMP5 mediates BRD4-dependent Pol II pause release and transcription of T-ALL genes C_LIO_LIP300-BRD4 induced enhancer and super-enhancer H3K27 acetylation requires CHMP5 C_LIO_LICHMP5 depletion mitigates chemoresistance and abrogates T-ALL initiation in vivo C_LI

cancer biology↗

bioRxiv2021

BET Bromodomain Inhibitors Target the NEUROD1-subtype SCLC by Blocking NEUROD1 Transactivation

Small cell lung cancer (SCLC) is a recalcitrant malignancy that urgently needs new therapies. Four master transcription factors (ASCL1, NEUROD1, POU2F3, and YAP1) are identified in SCLC, and each defines the transcriptome landscape of one molecular subtype. These master factors have not been directly druggable, and targeting their transcriptional coactivator(s) could provide an alternative approach. Here, we identify that BET bromodomain proteins physically interact with NEUROD1 and function as its transcriptional coactivators. Using CRISPR knockout and ChIP-seq, we demonstrate that NEUROD1 plays a critical role in defining the landscapes of BET bromodomain proteins in the SCLC genome. Targeting BET bromodomain proteins by BET inhibitors leads to broad suppression of the NEUROD1-target genes, especially those associated with superenhancers, and reduces SCLC growth in vitro and in vivo. LSAMP, a membrane protein in the IgLON family, was identified as one of the NEUROD1-target genes mediating BET inhibitor sensitivity in SCLC. Altogether, our study reveals that targeting transcriptional coactivators could be a novel approach to blocking the master transcription factors in SCLC for therapeutic purposes. SignificanceSmall cell lung cancer (SCLC) is the most aggressive form of lung malignancies, and little progress has been made to improve its outcome in the past two decades. It is now recognized that SCLC is not a single disease but has at least four molecular subtypes, and each subtype features the expression of one master transcription factor. Unfortunately, these master transcription factors are not directly druggable. Here, we identified BET bromodomain proteins as the transcriptional coactivators of NEUROD1, one of the master transcription factors in SCLC. Blocking BET bromodomain proteins with inhibitors suppresses NEUROD1-target genes and reduces tumor growth. Our results demonstrate that blocking transcriptional coactivators could be an alternative approach to targeting the master transcription factors in SCLC.

cancer biology↗

bioRxiv2018

Bromodomain Protein, BRD4, Contributes to the Regulation of Alternative Splicing

Bromodomain protein 4 (BRD4) is an atypical kinase and a histone acetyl transferase (HAT) which plays an important role in chromatin remodeling and early transcriptional elongation. During transcription elongation, BRD4 travels with the elongation complex. Since most of the alternative splicing events take place co-transcriptionally, we asked if BRD4 plays a role in regulation of alternative splicing. We find that distinct patterns of alternative splicing are associated with conditional deletion of BRD4 during thymocyte differentiation in vivo. Similarly, depletion of BRD4 in T-ALL cells alters patterns of splicing. Most of the alternatively spliced events affected by BRD4 are usage of exon skipping. In an established insulin receptor minigene model of splicing, BRD4 over expression modulates alternative splicing. Importantly, as assessed by both immunoprecipitation (IP) and proximity ligation (PLA) assays, BRD4 interacts with components of the splicing machinery. BRD4 also co-localizes on chromatin with one of the splicing regulators. We propose that BRD4 contributes to patterns of alternative splicing through its interaction with the splicing machinery during transcription elongation.\n\nSignificance StatementThe bromodomain protein, BRD4, is a transcriptional and epigenetic regulator that plays a critical role in both cancer and inflammation. It has pleiotropic activities, including chromatin organization, transcriptional pause release and initiation. We now report that it also contributes to the regulation of alternative splicing. Taken together, these findings indicate that BRD4 functions to coordinate the various steps in gene expression.

molecular biology↗