Hippocampal Knockout of p300 Affects Learning and Memory in Mice

Aging has been associated with cognitive decline, as seen in various learning and memory processes. Specifically, p300, a lysine acetyltransferase, has been shown to decrease with age, which could have an effect on cognition. In a series of behavioral tests, the effect of the knockout of p300 was studied in mice. In the water T maze test and the object recognition test, the results conveyed that the mice’s learning skills had not been impacted by the knockout of p300. But the water T maze test results further showed that the p300 knockout mice had a decline in their cognitive flexibility to new information. These findings suggest that the knockout of p300 has a negative impact on cognition. We expect that the overexpression of p300 in older mice will restore the cognition that might have been lost with aging.

Hydroxylation of the Acetyltransferase NAA10 Trp38 Is Not an Enzyme-Switch in Human Cells

NAA10 is a major N-terminal acetyltransferase (NAT) that catalyzes the cotranslational N-terminal (Nt-) acetylation of 40% of the human proteome. Several reports of lysine acetyltransferase (KAT) activity by NAA10 exist, but others have not been able to find any NAA10-derived KAT activity, the latter of which is supported by structural studies. The KAT activity of NAA10 towards hypoxia-inducible factor 1α (HIF-1α) was recently found to depend on the hydroxylation at Trp38 of NAA10 by factor inhibiting HIF-1α (FIH). In contrast, we could not detect hydroxylation of Trp38 of NAA10 in several human cell lines and found no evidence that NAA10 interacts with or is regulated by FIH. Our data suggest that NAA10 Trp38 hydroxylation is not a switch in human cells and that it alters its catalytic activity from a NAT to a KAT.

Differential expression of KAT6A in cancer of the vulva.

In these brief notes we document work using published microarray data (1, 2) to pioneer integrative transcriptome analysis comparing vulvar carcinoma to its tissue of origin, the vulva. We report the differential expression of lysine acetyltransferase 6A, encoded by KAT6A, in cancer of the vulva. KAT6A may be of pertinence to understanding transformation and disease progression in vulvar cancer (3).

Transcriptional variability accelerates pre-leukemia by cell diversification and perturbation of protein synthesis

Transcriptional variability facilitates stochastic cell diversification and can in turn underpin adaptation to stress or injury. We hypothesize that it may analogously facilitate progression of pre-malignancy to cancer. To investigate this, we initiated pre-leukemia in mouse cells with enhanced transcriptional variability due to conditional disruption of the histone lysine acetyltransferase gene Kat2a. By combining single-cell RNA-sequencing of pre-leukemia with functional analysis of transformation, we show that Kat2a loss results in global variegation of cell identity and accumulation of pre-leukemic cells. Leukemia progression is subsequently facilitated by destabilization of ribosome biogenesis and protein synthesis, which confer a transient transformation advantage. The contribution of transcriptional variability to early cancer evolution reflects a generic role in promoting cell fate transitions, which, in the case of well-adapted malignancies, contrastingly differentiates and depletes cancer stem cells. In other words, transcriptional variability confers forward momentum to cell fate systems, with differential multi-stage impact throughout cancer evolution.

A Budding Yeast Model and Screen to Define the Functional Consequences of Oncogenic Histone Missense Mutations

Somatic missense mutations in histone genes turn these essential proteins into oncohistones, which can drive oncogenesis. Understanding how missense mutations alter histone function is challenging in mammals as the changes occur in a single histone gene. For example, described oncohistone mutations predominantly occur in the histone H3.3 gene, despite the human genome encoding 15 H3 genes. To understand how oncogenic histone missense mutations alter histone function, we leverage the budding yeast model, which encodes only two H3 genes, to explore the functional consequences of oncohistones H3K36M, H3G34W, H3G34L, H3G34R, and H3G34V. An analysis of cells that express each of these variants as the sole copy of H3 reveals that H3K36-mutants show different drug sensitivities compared to H3G34 mutants. This finding suggests that changes to proximal amino acids in the H3 N-terminal tail alter distinct biological pathways. We exploited the caffeine sensitive growth of H3K36 mutant cells to perform a high copy suppressor screen. This screen identified genes linked to histone function and transcriptional regulation, the histone H4/H2A acetyltransferase, Esa1, a forkhead-associated domain-containing gene expression regulator, Tos4, an m6A RNA binding protein, Pho92, and a cyclin-dependent kinase, Sgv1/Bur1. We show that the Esa1 lysine acetyltransferase activity is critical for suppression of the caffeine sensitive growth of H3K36R mutant cells while neither of the characterized binding interactions of Tos4 nor Pho92 are required for suppression. Finally, Sgv1/Bur1-mediated suppression may occur through a dominant negative mechanism. This screen identifies pathways that could be altered by oncohistone mutations and highlights the value of yeast genetics to identify pathways altered by such mutations.

EP300 (p300) mediated histone butyrylation is critical for adipogenesis

The master epigenetic enzyme EP300 (p300) besides having lysine acetyltransferase activity can also catalyse other acylation modifications (propionylation, butyrylation, crotonylation etc.), the physiological implications of which are yet to be established. Here we report that lysine butyrylation concomittantly increases during adipogenesis, along with increased butyryl CoA levels due to upregulated fatty acid metabolic pathways. To delineate the role of p300 catalysed butyrylation in adipogenesis, we have identified a semi-synthetic derivative (LTK-14A) of garcinol which specifically inhibited histone butyrylation without affecting acetylation. Treatment of 3T3L1 cells with LTK-14A significantly abolished adipogenesis by downregulation of genes related to adipogenesis presumably through the inhibition of H4K5 butyrylation. Administering the specific inhibitor to high fat diet fed C57BL6/J mice as well as genetically obese db/db mice led to an attenuation/decrease in their weight gain respectively. The reduced obesity could be at least partially attributed to the targeted inhibition of H4K5 butyrylation, as observed by immunofluorescence staining of the inhibitor treated mice liver sections and immunoblotting with histones extracted from epididymal fat pads. This report therefore not only for the first time causally links histone butyrylation with adipogenesis but also presents a novel small molecule modulator that could be developed for anti-obesity therapeutics.

Targeted Protein Acetylation in Cells Using Heterobifunctional Molecules

Protein acetylation is a central event in orchestrating diverse cellular processes. However, current strategies to investigate protein acetylation in cells are often non-specific or lack temporal and magnitude control. Here, we developed an acetylation tagging system, AceTAG, to induce acetylation of targeted proteins. The AceTAG system utilizes bifunctional molecules to direct the lysine acetyltransferase p300/CBP to proteins fused with the small protein tag FKBP12F36V, resulting in their induced acetylation. Using AceTAG, we induced targeted acetylation of a diverse array of proteins in cells, specifically histone H3.3, the NF-kB subunit p65/RelA, and the tumor suppressor p53. We demonstrate that targeted acetylation with the AceTAG system is rapid, selective, reversible, and can be controlled in a dose-dependent fashion. AceTAG represents a useful strategy to modulate protein acetylation and will enable the exploration of targeted acetylation in basic biological and therapeutic contexts.

Rubinstein-Taybi Syndrome: A Model of Epigenetic Disorder

The Rubinstein-Taybi syndrome (RSTS) is a rare congenital developmental disorder characterized by a typical facial dysmorphism, distal limb abnormalities, intellectual disability, and many additional phenotypical features. It occurs at between 1/100,000 and 1/125,000 births. Two genes are currently known to cause RSTS, CREBBP and EP300, mutated in around 55% and 8% of clinically diagnosed cases, respectively. To date, 500 pathogenic variants have been reported for the CREBBP gene and 118 for EP300. These two genes encode paralogs acting as lysine acetyltransferase involved in transcriptional regulation and chromatin remodeling with a key role in neuronal plasticity and cognition. Because of the clinical heterogeneity of this syndrome ranging from the typical clinical diagnosis to features overlapping with other Mendelian disorders of the epigenetic machinery, phenotype/genotype correlations remain difficult to establish. In this context, the deciphering of the patho-physiological process underlying these diseases and the definition of a specific episignature will likely improve the diagnostic efficiency but also open novel therapeutic perspectives. This review summarizes the current clinical and molecular knowledge and highlights the epigenetic regulation of RSTS as a model of chromatinopathy.

HBO1 overexpression is important for hepatocellular carcinoma cell growth

Hepatocellular carcinoma (HCC) is a common primary liver malignancy lacking effective molecularly-targeted therapies. HBO1 (lysine acetyltransferase 7/KAT7) is a member of MYST histone acetyltransferase family. Its expression and potential function in HCC are studied. We show that HBO1 mRNA and protein expression is elevated in human HCC tissues and HCC cells. HBO1 expression is however low in cancer-surrounding normal liver tissues and hepatocytes. In HepG2 and primary human HCC cells, shRNA-induced HBO1 silencing or CRISPR/Cas9-induced HBO1 knockout potently inhibited cell viability, proliferation, migration, and invasion, while provoking mitochondrial depolarization and apoptosis induction. Conversely, ectopic overexpression of HBO1 by a lentiviral construct augmented HCC cell proliferation, migration and invasion. In vivo, xenografts-bearing HBO1-KO HCC cells grew significantly slower than xenografts with control HCC cells in severe combined immunodeficient mice. These results suggest HBO1 overexpression is important for HCC cell progression.