Biology subjects

Prinjha, R. K.

Publications and source records attributed to Prinjha, R. K..

4 recordsLinked to original sources

bioRxiv2022

Acute resistance to BET inhibitors remodels compensatory transcriptional programs via p300 co-activation

Initial clinical trials with drugs targeting epigenetic modulators - such as bromodomain and extraterminal (BET) inhibitors - demonstrate modest results in acute myeloid leukemia (AML). The main reason for this involves an increased transcriptional plasticity within AML, which allows cells to escape the therapeutic pressure. To study mechanisms of resistance, we investigated immediate epigenetic and transcriptional responses following BET inhibition, and could demonstrate that BET inhibitor-mediated release of BRD4 from chromatin is accompanied by an acute compensatory feedback loop that attenuates inhibition, or even increases expression, of specific transcriptional modules. This adaptation is most marked at key AML maintenance genes and is mediated by p300, suggesting a rational therapeutic opportunity by combining BET- and p300- inhibition. p300 activity is required during all steps of adaptation. However, the transcriptional programs that p300 regulates to induce resistance to BETi differ between AML subtypes. Remarkably, in some AMLs, p300 regulates a series of transitional transcriptional patterns that allow homeostatic adjustments during earlier stages of resistance to BET-inhibitors. In consequence, p300 remains crucial throughout all stages of resistance in sensitive AML-subtypes, although its importance declines following the development of chronic resistance to BET inhibitors in some other AMLs. Altogether, our study elucidates the mechanisms that underlie an "acute" state of resistance to BET inhibition, achieved through p300 activity, and how these mechanisms remodel to become "chronic". Importantly, however, our data also suggest that a sequential treatment with BET- and p300 inhibition may prevent resistance development, thereby improving outcomes. Key pointsO_LIA mechanistic feedback to p300 enables acute tolerance to BET inhibition. C_LIO_LIp300 regulates transcriptional networks that lead to chronic resistance to BET inhibition. C_LIO_LISequential BET-, followed by p300-inhibition, is synthetically lethal in AML, and is optimally deployed during earlier stages of resistance to BET inhibitors. C_LI

cancer biology↗

bioRxiv2020

Modulation of macrophage inflammatory function through selective inhibition of the epigenetic reader protein SP140

Speckled 140 KDa (SP140) is a nuclear body protein, mainly expressed in immune cells, which contains multiple domains suggestive of an epigenetic reader function; namely a bromodomain, a PHD domain and a SAND domain. Single nucleotide polymorphisms and epigenetic modifications in the SP140 locus have been linked to autoimmune and inflammatory diseases including Crohns disease (CD). However, little is known about the cellular function of SP140; this is due in part to the fact that, unlike for other many other epigenetic proteins, no small molecule inhibitors have been available to investigate the biological role of SP140. We report the discovery of the first small molecule SP140 inhibitor (GSK761) and utilize this to elucidate SP140 function in innate immune cells. We show that SP140 is highly expressed in CD68+ CD mucosal macrophages and in in vitro-generated inflammatory macrophages. SP140 inhibition through GSK761 reduced monocyte differentiation into inflammatory macrophages and lipopolysaccharide (LPS)-induced inflammatory activation, whilst inducing the generation of CD206+ regulatory macrophages that mark anti-TNF remission induction in CD patients. ChIP-seq analyses revealed that SP140 preferentially occupies transcriptional start sites (TSS) in inflammatory macrophages, with enrichment at gene loci encoding pro-inflammatory cytokines/chemokines and inflammatory pathways. GSK761 specifically reduced SP140 binding and thereby expression of SP140-dependent downstream inflammatory genes. Notably, in CD14+ macrophages isolated from CD intestinal-mucosa, GSK761 inhibited the spontaneous expression of cytokines, including TNF. Together, this study identifies SP140 as a druggable epigenetic reader and therapeutic target for CD.

immunology↗

bioRxiv2020

A histone-like motif in yellow fever virus contributes to viral replication

The mimicry of host proteins by viruses contributes to their ability to suppress antiviral immunity and hijack host biosynthetic machinery1. Host adaptation to evade this exploitation depends on host protein functional redundancy2. Non-redundant, essential host proteins have limited potential to adapt without severe consequences3. Histones, which are essential for genome architecture and control of gene expression, are among the most evolutionary conserved proteins4. Here we show that the capsid protein of the flavivirus yellow fever virus (YFV), mimics histone H4 and interferes with chromatin gene regulation by BRD4, a bromodomain and extraterminal domain (BET) protein. Two acetyl-lysine residues of YFV capsid are embedded in a histone-like motif that interacts with the BRD4 bromodomain, affecting gene expression and influencing YFV replication. These findings reveal histone mimicry as a strategy employed by an RNA virus that replicates in the cytosol5 and define convergent and distinct molecular determinants for motif recognition of the viral mimic versus histone H4.

microbiology↗

bioRxiv2019

Histone H3K27me3 demethylases regulate human Th17 cell development and effector functions by impacting on metabolism

T helper (Th) cells are CD4+ effector T cells that play an instrumental role in immunity by shaping the inflammatory cytokine environment in a variety of physiological and pathological situations. Using a combined chemico-genetic approach we identify histone H3K27 demethylases KDM6A and KDM6B as central regulators of human Th subsets. The prototypic KDM6 inhibitor GSK-J4 increases genome-wide levels of the repressive H3K27me3 chromatin mark and leads to suppression of the key transcription factor ROR{gamma}t during Th17 differentiation, whereas in mature Th17 cells an altered transcriptional program leads to a profound metabolic reprogramming with concomitant suppression of IL-17 cytokine levels and reduced proliferation. Single cell analysis reveals a specific shift from highly inflammatory cell subsets towards a resting state upon demethylase inhibition. The root cause of the observed anti-inflammatory phenotype in stimulated Th17 cells is reduced expression of key metabolic transcription factors, such as PPRC1 and c-myc. Overall, this leads to reduced mitochondrial biogenesis resulting in a metabolic switch with concomitant anti-inflammatory effects. These data are consistent with an opposing effect of GSK-J4 on Th17 T-cell differentiation pathways directly related to proliferation and effector cytokine profiles.

immunology↗