Transcriptional/epigenetic regulator CBP/p300 in tumorigenesis: structural and functional versatility in target recognition

Diagnosis and management in Rubinstein-Taybi syndrome: first international consensus statement

Rubinstein-Taybi syndrome (RTS) is an archetypical genetic syndrome that is characterised by intellectual disability, well-defined facial features, distal limb anomalies and atypical growth, among numerous other signs and symptoms. It is caused by variants in either of two genes (CREBBP, EP300) which encode for the proteins CBP and p300, which both have a function in transcription regulation and histone acetylation. As a group of international experts and national support groups dedicated to the syndrome, we realised that marked heterogeneity currently exists in clinical and molecular diagnostic approaches and care practices in various parts of the world. Here, we outline a series of recommendations that document the consensus of a group of international experts on clinical diagnostic criteria for types of RTS (RTS1: CREBBP; RTS2: EP300), molecular investigations, long-term management of various particular physical and behavioural issues and care planning. The recommendations as presented here will need to be evaluated for improvements to allow for continued optimisation of diagnostics and care.

CBP/P300 BRD Inhibition Reduces Neutrophil Accumulation and Activates Antitumor Immunity in TNBC

Tumor-associated neutrophils (TANs) have been shown to promote immunosuppression and tumor progression, and a high TAN frequency predicts poor prognosis in triple-negative breast cancer (TNBC). Dysregulation of CREB binding protein (CBP)/P300 function has been observed with multiple cancer types. The bromodomain (BRD) of CBP/P300 has been shown to regulate its activity. In this study, we found that IACS-70654, a novel and selective CBP/P300 BRD inhibitor, reduced TANs and inhibited the growth of neutrophil-enriched TNBC models. In the bone marrow, CBP/P300 BRD inhibition reduced the tumor-driven abnormal differentiation and proliferation of neutrophil progenitors. Inhibition of CBP/P300 BRD also stimulated the immune response by inducing an IFN response and MHCI expression in tumor cells and increasing tumor-infiltrated CTLs. Moreover, IACS-70654 improved the response of a neutrophil-enriched TNBC model to docetaxel and immune checkpoint blockade. This provides a rationale for combining a CBP/P300 BRD inhibitor with standard-of-care therapies in future clinical trials for neutrophil-enriched TNBC.

Summary

In neutrophil-enriched triple-negative breast cancer (TNBC) models, CREB binding protein (CBP)/P300 bromodomain (BRD) inhibition reduces tumor growth and systemic neutrophil accumulation while stimulating an antitumor immune response. This improves standard-of-care therapies, suggesting a potential therapeutic benefit of CBP/P300 BRD inhibitors for neutrophil-enriched TNBC.

Discovery of Highly Potent and Efficient CBP/p300 Degraders with Strong In Vivo Antitumor Activity

The transcriptional coactivator cAMP response element binding protein (CREB)-binding protein (CBP) and its homologue p300 have emerged as attractive therapeutic targets for human cancers such as acute myeloid leukemia (AML). Herein, we report the design, synthesis, and biological evaluation of a series of cereblon (CRBN)-recruiting CBP/p300 proteolysis targeting chimeras (PROTACs) based on the inhibitor CCS1477. The representative compounds 14g (XYD190) and 14h (XYD198) potently inhibited the growth of AML cells with low nanomolar IC50 values and effectively degraded CBP and p300 proteins in a concentration- and time-dependent manner. Mechanistic studies confirmed that 14g and 14h can selectively bind to CBP/p300 bromodomains and induce CBP and p300 degradation in bromodomain family proteins in a CRBN- and proteasome-dependent manner. 14g and 14h displayed remarkable antitumor efficacy in the MV4;11 xenograft model (TGI = 88% and 93%, respectively). Our findings demonstrated that 14g and 14h are useful lead compounds and deserve further optimization and activity evaluation for the treatment of human cancers.

The winged helix domain of MORF binds CpG islands and the TAZ2 domain of p300

Acetylation of histones by lysine acetyltransferases (KATs) provides a fundamental mechanism by which chromatin structure and transcriptional programs are regulated. Here, we describe a dual binding activity of the first winged helix domain of human MORF KAT (MORFWH1) that recognizes the TAZ2 domain of p300 KAT (p300TAZ2) and CpG rich DNA sequences. Structural and biochemical studies identified distinct DNA and p300TAZ2 binding sites, allowing MORFWH1 to independently engage either ligand. Genomic data show that MORF/MOZWH1 colocalizes with H3K18ac, a product of enzymatic activity of p300, on CpG rich promoters of target genes. Our findings suggest a functional cooperation of MORF and p300 KATs in transcriptional regulation.

Androgen receptor cofactors: A potential role in understanding prostate cancer

Prostate cancer (PCa) is witnessing a concerning rise in incidence annually, with the androgen receptor (AR) emerging as a pivotal contributor to its growth and progression. Mounting evidence underscores the AR's ability to recruit cofactors, influencing downstream gene transcription and thereby fueling the proliferation and metastasis of PCa cells. Although, clinical strategies involving AR antagonists provide some relief, managing castration resistant prostate cancer (CRPC) remains a formidable challenge. Thus, the need of the hour lies in unearthing new drugs or therapeutic targets to effectively combat PCa. This review encapsulates the pivotal roles played by coactivators and corepressors of AR, notably androgen receptor-associated protein (ARA) and steroid receptor Coactivators (SRC) in PCa. Our data unveils how these cofactors intricately modulate histone modifications, cell cycling, SUMOylation, and apoptosis through their interactions with AR. Among the array of cofactors scrutinised, such as ARA70β, ARA24, ARA160, ARA55, ARA54, PIAS1, PIAS3, SRC1, SRC2, SRC3, PCAF, p300/CBP, MED1, and CARM1, several exhibit upregulation in PCa. Conversely, other cofactors like ARA70α, PIASy, and NCoR/SMRT demonstrate downregulation. This duality underscores the complexity of AR cofactor dynamics in PCa. Based on our findings, we propose that manipulating cofactor regulation to modulate AR function holds promise as a novel therapeutic avenue against advanced PCa. This paradigm shift offers renewed hope in the quest for effective treatments in the face of CRPC's formidable challenges.

Near infrared-responsive quinacrine-gold hybrid nanoparticles deregulate HSP-70/P300-mediated H3K14 acetylation in ER/PR+ breast cancer stem cells

Aim: This study aimed to determine if quinacrine-gold hybrid nanoparticles (QAuNPs) + near-infrared (NIR) deregulate HSP-70/P300 complex-mediated H3K14 acetylation in estrogen receptor/progesterone receptor (ER/PR+) breast cancer stem cells (CSCs). Materials & methods: Various cells and mouse-based systems were used as models. Results: QAuNP + NIR treatment reduced the nuclear translocation of HSP-70, affected the histone acetyltransferase activity of P300 and specifically decreased H3K14 acetylation in ER/PR+ breast CSCs. Finally, HSP-70 knockdown showed a reduction in P300 histone acetyltransferase activity, decreased H3K14 acetylation and inhibited activation of the TGF-β gene. Conclusion: This study revealed that QAuNP + NIR irradiation inhibits oncogenic activation of the TGF-β gene by decreasing H3K14 acetylation mediated through the HSP-70/P300 nuclear complex in ER/PR+ breast CSCs.

Cell fate regulation governed by p53: Friends or reversible foes in cancer therapy

Cancer is a leading cause of death worldwide. Targeted therapies aimed at key oncogenic driver mutations in combination with chemotherapy and radiotherapy as well as immunotherapy have benefited cancer patients considerably. Tumor protein p53 (TP53), a crucial tumor suppressor gene encoding p53, regulates numerous downstream genes and cellular phenotypes in response to various stressors. The affected genes are involved in diverse processes, including cell cycle arrest, DNA repair, cellular senescence, metabolic homeostasis, apoptosis, and autophagy. However, accumulating recent studies have continued to reveal novel and unexpected functions of p53 in governing the fate of tumors, for example, functions in ferroptosis, immunity, the tumor microenvironment and microbiome metabolism. Among the possibilities, the evolutionary plasticity of p53 is the most controversial, partially due to the dizzying array of biological functions that have been attributed to different regulatory mechanisms of p53 signaling. Nearly 40 years after its discovery, this key tumor suppressor remains somewhat enigmatic. The intricate and diverse functions of p53 in regulating cell fate during cancer treatment are only the tip of the iceberg with respect to its equally complicated structural biology, which has been painstakingly revealed. Additionally, TP53 mutation is one of the most significant genetic alterations in cancer, contributing to rapid cancer cell growth and tumor progression. Here, we summarized recent advances that implicate altered p53 in modulating the response to various cancer therapies, including chemotherapy, radiotherapy, and immunotherapy. Furthermore, we also discussed potential strategies for targeting p53 as a therapeutic option for cancer.

p300 is an obligate integrator of combinatorial transcription factor inputs

Transcription coactivators are proteins or protein complexes that mediate transcription factor (TF) function. However, they lack DNA-binding capacity, prompting the question of how they engage target loci. Three non-exclusive hypotheses have been posited: coactivators are recruited by complexing with TFs, by binding histones through epigenetic reader domains, or by partitioning into condensates through their extensive intrinsically disordered regions. Using p300 as a prototypical coactivator, we systematically mutated its annotated domains and show by single-molecule tracking in live U2OS cells that coactivator-chromatin binding depends entirely on combinatorial binding of multiple TF-interaction domains. Furthermore, we demonstrate that acetyltransferase activity opposes p300-chromatin association and that the N-terminal TF-interaction domains regulate that activity. Single TF-interaction domains are insufficient for chromatin binding and regulation of catalytic activity, implying a principle that we speculate could broadly apply to eukaryotic gene regulation: a TF must act in coordination with other TFs to recruit coactivator activity.

In silico screening and identification of potential drug against p300 acetyltransferase activity in breast cancer via drug repurposing approach

Emerging evidence portray the involvement of epigenomic reprogramming in the onset and progression of several malignancies, including breast cancer. Histone acetyltransferase (HAT) p300 is a critical epigenetic regulator that acts as a transcription co-activator and regulates various cellular processes. p300 is overexpressed in breast cancer and promotes cellular invasion and survival, making it a promising druggable target. In this study, the relevance of p300 in different cancer pathways was established. Virtual screening of the FDA-approved drug library was carried out using molecular docking, and the top 10 potential repurposed drugs were identified. Further, recalculation of binding free energy of drug-p300 complexes was carried out using molecular mechanics Poisson-Boltzmann and surface area (MM-PBSA) method after molecular dynamic simulation. Based on molecular dynamic simulation parameters and binding free energy analysis, two drugs, namely Netarsudil (-305.068 kJ/mol) and Imatinib (-260.457 kJ/mol), were identified as potential repurposed drugs to inhibit the activity of p300. In conclusion, these findings suggest, Netarsudil and Imatinib might be a potential repurposed drug to combat breast cancer via p300 inhibition.Communicated by Ramaswamy H. Sarma.

Structural basis of CBP/p300 recruitment by the microphthalmia-associated transcription factor

The microphthalmia-associated transcription factor (MITF) is a master regulator of the melanocyte cell lineage. Aberrant MITF activity can lead to multiple malignancies including skin cancer, where it modulates the progression and invasiveness of melanoma. MITF-regulated gene expression requires recruitment of the transcriptional co-regulator CBP/p300, but details of this process are not fully defined. In this study, we investigate the structural and functional interaction between the MITF N-terminal transactivation domain (MITFTAD) and CBP/p300. Using pulldown assays and nuclear magnetic resonance spectroscopy we determined that MITFTAD is intrinsically disordered and binds to the TAZ1 and TAZ2 domains of CBP/p300 with moderate affinity. The solution-state structure of the MITFTAD:TAZ2 complex reveals that MITF interacts with a hydrophobic surface of TAZ2, while remaining somewhat dynamic. Peptide array and mutagenesis experiments determined that an acidic motif is integral to the MITFTAD:TAZ2 interaction and is necessary for transcriptional activity of MITF. Peptides that bind to the same surface of TAZ2 as MITFTAD, such as the adenoviral protein E1A, are capable of displacing MITF from TAZ2 and inhibiting transactivation. These findings provide insight into co-activator recruitment by MITF that are fundamental to our understanding of MITF targeted gene regulation and melanoma biology.

Fine tuning of the transcription juggernaut: A sweet and sour saga of acetylation and ubiquitination

Among post-translational modifications of proteins, acetylation, phosphorylation, and ubiquitination are most extensively studied over the last several decades. Owing to their different target residues for modifications, cross-talk between phosphorylation with that of acetylation and ubiquitination is relatively less pronounced. However, since canonical acetylation and ubiquitination happen only on the lysine residues, an overlap of the same lysine residue being targeted for both acetylation and ubiquitination happens quite frequently and thus plays key roles in overall functional regulation predominantly through modulation of protein stability. In this review, we discuss the cross-talk of acetylation and ubiquitination in the regulation of protein stability for the functional regulation of cellular processes with an emphasis on transcriptional regulation. Further, we emphasize our understanding of the functional regulation of Super Elongation Complex (SEC)-mediated transcription, through regulation of stabilization by acetylation, deacetylation and ubiquitination and associated enzymes and its implication in human diseases.

Mechanistic insights into the dual role of CCAR2/DBC1 in cancer

Cell cycle and apoptosis regulator 2 (CCAR2), also known as deleted in breast cancer 1 (DBC1), has been recently identified as a master regulator of transcriptional processes and plays diverse roles in physiology and pathophysiology, including as a regulator of apoptosis, DNA repair, metabolism, and tumorigenesis. CCAR2 functions as a coregulator of various transcription factors and a critical regulator of numerous epigenetic modifiers. Based on its ability to stimulate apoptosis by activating and stabilizing p53, CCAR2 was initially considered to be a tumor suppressor. However, an increasing number of studies have shown that CCAR2 also functions as a tumor-promoting coregulator by activating oncogenic transcription factors and regulating the enzymatic activity of epigenetic modifiers, indicating that CCAR2 may play a dual role in cancer progression by acting as a tumor suppressor and tumor promoter. Here, we review recent progress in understanding the dual tumor-suppressing and oncogenic roles of CCAR2 in cancer. We discuss CCAR2 domain structures, its interaction partners, and the molecular mechanisms by which it regulates the activities of transcription factors and epigenetic modifiers.

Analysis of PPI networks of transcriptomic expression identifies hub genes associated with Newcastle disease virus persistent infection in bladder cancer

Bladder cancer cells can acquire persistent infection of oncolytic Newcastle disease virus (NDV) but the molecular mechanism(s) remain unelucidated. This poses a major barrier to the effective clinical translation of oncolytic NDV virotherapy of cancers. To improve our understanding of the molecular mechanism(s) associated with the development of NDV persistent infection in bladder cancer, we used mRNA expression profiles of persistently infected bladder cancer cells to construct PPI networks. Based on paths and modules in the PPI network, the bridges were found mainly in the upregulated mRNA-pathways of p53 signalling, ECM-receptor interaction, and TGF-beta signalling and downregulated mRNA-pathways of antigen processing and presentation, protein processing in endoplasmic reticulum, completement and coagulation cascades in persistent TCCSUPPi cells. In persistent EJ28Pi cells, connections were identified mainly through upregulated mRNA-pathways of renal carcinoma, viral carcinogenesis, Ras signalling and cell cycle and the downregulated mRNA-pathways of Wnt signalling, HTLV-I infection and pathways in cancers. These connections were mainly dependent on RPL8-HSPA1A/HSPA4 in TCCSUPPi cells and EP300, PTPN11, RAC1-TP53, SP1, CCND1 and XPO1 in EJ28Pi cells. Oncomine validation showed that the top hub genes identified in the networks that include RPL8, THBS1, F2 from TCCSUPPi and TP53 and RAC1 from EJ28Pi are involved in the development and progression of bladder cancer. Protein-drug interaction networks identified several putative drug targets that could be used to disrupt the linkages between the modules and prevent bladder cancer cells from acquiring NDV persistent infection. This novel PPI network analysis of differentially expressed mRNAs of NDV persistently infected bladder cancer cell lines provide an insight into the molecular mechanisms of NDV persistency of infection in bladder cancers and the future screening of drugs that can be used together with NDV to enhance its oncolytic efficacy.

Effects of the Acetyltransferase p300 on Tumour Regulation from the Novel Perspective of Posttranslational Protein Modification

p300 acts as a transcription coactivator and an acetyltransferase that plays an important role in tumourigenesis and progression. In previous studies, it has been confirmed that p300 is an important regulator in regulating the evolution of malignant tumours and it also has extensive functions. From the perspective of non-posttranslational modification, it has been proven that p300 can participate in regulating many pathophysiological processes, such as activating oncogene transcription, promoting tumour cell growth, inducing apoptosis, regulating immune function and affecting embryo development. In recent years, p300 has been found to act as an acetyltransferase that catalyses a variety of protein modification types, such as acetylation, propanylation, butyylation, 2-hydroxyisobutyration, and lactylation. Under the catalysis of this acetyltransferase, it plays its crucial tumourigenic driving role in many malignant tumours. Therefore, the function of p300 acetyltransferase has gradually become a research hotspot. From a posttranslational modification perspective, p300 is involved in the activation of multiple transcription factors and additional processes that promote malignant biological behaviours, such as tumour cell proliferation, migration, and invasion, as well as tumour cell apoptosis, drug resistance, and metabolism. Inhibitors of p300 have been developed and are expected to become novel anticancer drugs for several malignancies. We review the characteristics of the p300 protein and its functional role in tumour from the posttranslational modification perspective, as well as the current status of p300-related inhibitor research, with a view to gaining a comprehensive understanding of p300.

SMN post-translational modifications in spinal muscular atrophy

Since its first identification as the gene responsible for spinal muscular atrophy (SMA), the range of survival motor neuron (SMN) protein functions has increasingly expanded. This multimeric complex plays a crucial role in a variety of RNA processing pathways. While its most characterized function is in the biogenesis of ribonucleoproteins, several studies have highlighted the SMN complex as an important contributor to mRNA trafficking and translation, axonal transport, endocytosis, and mitochondria metabolism. All these multiple functions need to be selectively and finely modulated to maintain cellular homeostasis. SMN has distinct functional domains that play a crucial role in complex stability, function, and subcellular distribution. Many different processes were reported as modulators of the SMN complex activities, although their contribution to SMN biology still needs to be elucidated. Recent evidence has identified post-translational modifications (PTMs) as a way to regulate the pleiotropic functions of the SMN complex. These modifications include phosphorylation, methylation, ubiquitination, acetylation, sumoylation, and many other types. PTMs can broaden the range of protein functions by binding chemical moieties to specific amino acids, thus modulating several cellular processes. Here, we provide an overview of the main PTMs involved in the regulation of the SMN complex with a major focus on the functions that have been linked to SMA pathogenesis.

Recent Advances on Small-Molecule Bromodomain-Containing Histone Acetyltransferase Inhibitors

In recent years, substantial research has been conducted on molecular mechanisms and inhibitors targeting bromodomains (BRDs) and extra-terminal (BET) family proteins. On this basis, non-BET BRD is gradually becoming a research hot spot. BRDs are abundant in histone acetyltransferase (HAT)-associated activating transcription factors, and BRD-containing HATs have been linked to cancer, inflammation, and viral replication. Therefore, the development of BRD-containing HATs as chemical probes is useful for understanding the specific biological roles of BRDs in diseases and drug discovery. Several types of BRD-containing HATs, including CBP/P300, PCAF/GCN5, and TAF1, are discussed in this context in terms of their structures, functions, and small-molecule inhibitors. Additionally, progress in BRD inhibitors/chemical probes and proteolysis targeting chimeras in terms of drug design, biological activity, and disease application are summarized. These findings provide insights into the development of BRD inhibitors as potential drug candidates for various diseases.

HDAC4 in cancer: A multitasking platform to drive not only epigenetic modifications

Controlling access to genomic information and maintaining its stability are key aspects of cell life. Histone acetylation is a reversible epigenetic modification that allows access to DNA and the assembly of protein complexes that regulate mainly transcription but also other activities. Enzymes known as histone deacetylases (HDACs) are involved in the removal of the acetyl-group or in some cases of small hydrophobic moieties from histones but also from the non-histone substrate. The main achievement of HDACs on histones is to repress transcription and promote the formation of more compact chromatin. There are 18 different HDACs encoded in the human genome. Here we will discuss HDAC4, a member of the class IIa family, and its possible contribution to cancer development.

Vitamin D, a Secosteroid Hormone and Its Multifunctional Receptor, Vitamin D Receptor, in Alzheimer's Type Neurodegeneration

Vitamin D is a secosteroid hormone exerting neurosteroid-like properties. Its well-known nuclear hormone receptor, and recently proposed as a mitochondrial transcription factor, vitamin D receptor, acts for its primary functions. The second receptor is an endoplasmic reticulum protein, protein disulfide isomerase A3 (PDIA3), suggested to act as a rapid response. Vitamin D has effects on various systems, particularly through calcium metabolism. Among them, the nervous system has an important place in the context of our subject. Recent studies have shown that vitamin D and its receptors have numerous effects on the nervous system. Neurodegeneration is a long-term process. Throughout a human life span, so is vitamin D deficiency. Our previous studies and others have suggested that the out-come of long-term vitamin D deficiency (hypovitaminosis D or inefficient utilization of vitamin D), may lead neurons to be vulnerable to aging and neurodegeneration. We suggest that keeping vitamin D levels at adequate levels at all stages of life, considering new approaches such as agonists that can activate vitamin D receptors, and utilizing other derivatives produced in the synthesis process with UVB are crucial when considering vitamin D-based intervention studies. Given most aspects of vitamin D, this review outlines how vitamin D and its receptors work and are involved in neurodegeneration, emphasizing Alzheimer's disease.

HAT- and HDAC-Targeted Protein Acetylation in the Occurrence and Treatment of Epilepsy

Epilepsy is a common and severe chronic neurological disorder. Recently, post-translational modification (PTM) mechanisms, especially protein acetylation modifications, have been widely studied in various epilepsy models or patients. Acetylation is regulated by two classes of enzymes, histone acetyltransferases (HATs) and histone deacetylases (HDACs). HATs catalyze the transfer of the acetyl group to a lysine residue, while HDACs catalyze acetyl group removal. The expression of many genes related to epilepsy is regulated by histone acetylation and deacetylation. Moreover, the acetylation modification of some non-histone substrates is also associated with epilepsy. Various molecules have been developed as HDAC inhibitors (HDACi), which have become potential antiepileptic drugs for epilepsy treatment. In this review, we summarize the changes in acetylation modification in epileptogenesis and the applications of HDACi in the treatment of epilepsy as well as the mechanisms involved. As most of the published research has focused on the differential expression of proteins that are known to be acetylated and the knowledge of whole acetylome changes in epilepsy is still minimal, a further understanding of acetylation regulation will help us explore the pathological mechanism of epilepsy and provide novel ideas for treating epilepsy.

NAA60 (HAT4): the newly discovered bi-functional Golgi member of the acetyltransferase family

Chromatin structural organization, gene expression and proteostasis are intricately regulated in a wide range of biological processes, both physiological and pathological. Protein acetylation, a major post-translational modification, is tightly involved in interconnected biological networks, modulating the activation of gene transcription and protein action in cells. A very large number of studies describe the pivotal role of the so-called acetylome (accounting for more than 80% of the human proteome) in orchestrating different pathways in response to stimuli and triggering severe diseases, including cancer. NAA60/NatF (N-terminal acetyltransferase F), also named HAT4 (histone acetyltransferase type B protein 4), is a newly discovered acetyltransferase in humans modifying N-termini of transmembrane proteins starting with M-K/M-A/M-V/M-M residues and is also thought to modify lysine residues of histone H4. Because of its enzymatic features and unusual cell localization on the Golgi membrane, NAA60 is an intriguing acetyltransferase that warrants biochemical and clinical investigation. Although it is still poorly studied, this review summarizes current findings concerning the structural hallmarks and biological role of this novel targetable epigenetic enzyme.

cAMP-Dependent Signaling and Ovarian Cancer

cAMP-dependent pathway is one of the most significant signaling cascades in healthy and neoplastic ovarian cells. Working through its major effector proteins-PKA and EPAC-it regulates gene expression and many cellular functions. PKA promotes the phosphorylation of cAMP response element-binding protein (CREB) which mediates gene transcription, cell migration, mitochondrial homeostasis, cell proliferation, and death. EPAC, on the other hand, is involved in cell adhesion, binding, differentiation, and interaction between cell junctions. Ovarian cancer growth and metabolism largely depend on changes in the signal processing of the cAMP-PKA-CREB axis, often associated with neoplastic transformation, metastasis, proliferation, and inhibition of apoptosis. In addition, the intracellular level of cAMP also determines the course of other pathways including AKT, ERK, MAPK, and mTOR, that are hypo- or hyperactivated among patients with ovarian neoplasm. With this review, we summarize the current findings on cAMP signaling in the ovary and its association with carcinogenesis, multiplication, metastasis, and survival of cancer cells. Additionally, we indicate that targeting particular stages of cAMP-dependent processes might provide promising therapeutic opportunities for the effective management of patients with ovarian cancer.

CXCL1 promotes colon cancer progression through activation of NF-κB/P300 signaling pathway

BACKGROUND

The upregulated expression of CXCL1 has been validated in colorectal cancer patients. As a potential biotherapeutic target for colorectal cancer, the mechanism by which CXCL1 affects the development of colorectal cancer is not clear.

METHODS

Expression data of CXCL1 in colorectal cancer were obtained from the GEO database and verified using the GEPIA database and the TIMER 2.0 database. Knockout and overexpression of CXCL1 in colorectal cancer cells by CRISPR/Cas and "Sleeping Beauty" transposon-mediated gene editing techniques. Cell biological function was demonstrated by CCK-8, transwell chamber and Colony formation assay. RT-qPCR and Western Blot assays measured RNA and protein expression. Protein localization and expression were measured by immunohistochemistry and immunofluorescence.

RESULTS

Bioinformatics analysis showed significant overexpression of CXCL1 in the colorectal cancer tissues compared to normal human tissues, and identified CXCL1 as a potential therapeutic target for colorectal cancer. We demonstrate that CXCL1 promotes the proliferation and migration of colon cancer cells and has a facilitative effect on tumor angiogenesis. Furthermore, CXCL1 elevation promoted the migration of M2-tumor associated macrophages (TAMs) while disrupting the aggregation of CD4+ and CD8+ T cells at tumor sites. Mechanistic studies suggested that CXCL1 activates the NF-κB pathway. In the in vivo colon cancer transplantation tumor model, treatment with the P300 inhibitor C646 significantly inhibited the growth of CXCL1-overexpressing colon cancer.

CONCLUSION

CXCL1 promotes colon cancer development through activation of NF-κB/P300, and that CXCL1-based therapy is a potential novel strategy to prevent colon cancer development.

Structural insights revealed by the cocrystal structure of CCS1477 in complex with CBP bromodomain

Inhibition of the bromodomain of the CREB (cyclic-AMP response element-binding protein) binding protein (CBP) is a particularly promising new therapeutic approach for cancer. Benzimidazole derivatives CCS1477 and its analogues (8 and 9) are highly potent and selective CBP bromodomain inhibitors, with K_d values of 26.4, 37.0, and 34.3 nM in ITC assay, respectively. Among these compounds, CCS1477 is undergoing phase Ib/IIa clinical trials for the treatment of various cancers. Thus, we determined the co-crystal structures of CCS1477 and its analogues in complex with CBP bromodomain and revealed the detailed binding modes. Furthermore, overlapping with other reported co-crystal structures allowed us to identify that interaction with Arg1173, LPF shelf, and ZA channel was critical for keeping strong biological activity and selectivity. Collectively, this study provided a structural basis for CBP bromodomain inhibitors design.

Discovery of novel benzimidazole derivatives as potent p300 bromodomain inhibitors with anti-proliferative activity in multiple cancer cells

Adenovirus E1A-associated 300-k_D protein (p300) bromodomain, which regulates gene expression by recognizing acetylated lysine (KAc) of histone, is a promising target for the treatment of cancer. Herein, a series of potent p300 bromodomain inhibitors with novel CBP30-based scaffolds was discovered through bioisosterism and conformational restriction strategies. The most promising compound 1u showed more potent inhibitory activity (IC₅₀ = 49 nM) against p300 bromodomain and anti-proliferative activity in various cancer cell lines compared to CBP30. Moreover, 1u suppressed the expression of c-Myc and induced G₁/G₀ phase arrest and apoptosis in OPM-2 cells more potently than CBP30. This study provides new lead compounds for further research on the biological functions of p300.

Structural basis for binding diversity of acetyltransferase p300 to the nucleosome

p300 is a human acetyltransferase that associates with chromatin and mediates vital cellular processes. We now report the cryo-electron microscopy structures of the p300 catalytic core in complex with the nucleosome core particle (NCP). In the most resolved structure, the HAT domain and bromodomain of p300 contact nucleosomal DNA at superhelical locations 2 and 3, and the catalytic site of the HAT domain are positioned near the N-terminal tail of histone H4. Mutations of the p300-DNA interfacial residues of p300 substantially decrease binding to NCP. Three additional classes of p300-NCP complexes show different modes of the p300-NCP complex formation. Our data provide structural details critical to our understanding of the mechanism by which p300 acetylates multiple sites on the nucleosome.

TRPM3-Induced Gene Transcription Is under Epigenetic Control

Transient receptor potential M3 (TRPM3) cation channels regulate numerous biological functions, including gene transcription. Stimulation of TRPM3 channels with pregnenolone sulfate activates stimulus-responsive transcription factors, which bind to short cognate sequences in the promoters of their target genes. In addition, coregulator proteins are involved that convert the chromatin into a configuration that is permissive for gene transcription. In this study, we determined whether TRPM3-induced gene transcription requires coactivators that change the acetylation pattern of histones. We used compound A485, a specific inhibitor of the histone acetyltransferases CBP and p300. In addition, the role of bromodomain proteins that bind to acetylated lysine residues of histones was analyzed. We used JQ1, an inhibitor of bromodomain and extra terminal domain (BET) family proteins. The results show that both compounds attenuated the activation of AP-1 and CREB-regulated gene transcription following stimulation of TRPM3 channels. Inhibition of CBP/p300 and BET proteins additionally reduced the transcriptional activation potential of the transcription factors c-Fos and Elk-1. Transcriptional upregulation of the interleukin-8 gene was attenuated by A485 and JQ1, indicating that proinflammatory cytokine expression is controlled by CBP/p300 and bromodomain proteins. We conclude that TRPM3-induced signaling involves transcriptional coactivators and acetyl-lysine-bound bromodomain proteins for activating gene transcription.

Structure-activity relationship and antitumor activity of 1,4-pyrazine-containing inhibitors of histone acetyltransferases P300/CBP

Acetylation of histone lysine residues by histone acetyltransferase (HAT) p300 and its paralog CBP play important roles in gene regulation in health and diseases. The HAT domain of p300/CBP has been found to be a potential drug target for cancer. Compound screening followed by structure-activity relationship studies yielded a novel series of 1,4-pyrazine-containing inhibitors of p300/CBP HAT with their IC50s as low as 1.4 μM. Enzyme kinetics and other studies support the most potent compound 29 is a competitive inhibitor of p300 HAT against the substrate histone. It exhibited a high selectivity for p300 and CBP, with negligible activity on other classes of HATs in human. Compound 29 inhibited cellular acetylation of several histone lysine residues and showed strong activity against proliferation of a panel of solid and blood cancer cells. These results indicate it is a novel pharmacological lead for drug development targeting these cancers as well as a useful chemical probe for biological studies of p300/CBP.

Kinetic Analysis of the Effect of N-Terminal Acetylation on Thymine DNA Glycosylase

Thymine DNA glycosylase (TDG) is tasked with initiating DNA base excision repair by recognizing and removing T, U, the chemotherapeutic 5-fluorouracil (5-FU), and many other oxidized and halogenated pyrimidine bases. TDG contains a long, unstructured N-terminus that contains four known sites of acetylation: lysine (K) residues 59, 83, 84, and 87. Here, K to glutamine (Q) mutants are used as acetyl-lysine (AcK) analogues to probe the effect of N-terminal acetylation on the kinetics of TDG. We find that mimicking acetylation affects neither the maximal single-turnover rate k_max nor the turnover rate k_TO, indicating that the steps after initial binding, through chemistry and product release, are not affected. Under subsaturating conditions, however, acetylation changes the processing of U substrates. Subtle differences among AcK analogues are revealed with 5-FU in single-stranded DNA. We propose that the subtleties observed among the AcK analogues may be amplified on the genomic scale, leading to regulation of TDG activity. N-terminal acetylation, though, may also play a structural, rather than kinetic role in vivo.

SETD5 Regulates Glycolysis in Breast Cancer Stem-Like Cells and Fuels Tumor Growth

Although glycolysis plays a pivotal role in breast cancer stem-like cell (BCSC) reprogramming, the molecular mechanisms that couple glycolysis to cancer stem-like cells remain unclear. SETD5 is a previously uncharacterized member of the histone lysine methyltransferase family. The goal of this study was to explore the mechanisms underlying the promotion of stem-like and glycolysis activation traits by SETD5. Previous studies have shown that overexpression of SETD5 in breast cancer tissues is associated positively with progression. The present study showed that SETD5 expression was enriched in BCSCs. Down-regulation of SETD5 significantly decreased BCSC properties and glycolysis in vitro and in vivo. Interestingly, SETD5 and glycolytic enzymes were accumulated in the central hypoxic regions of subcutaneous tumor tissues. Bioinformatic analysis predicted SETD5 binding to E1A binding protein p300 (EP300), and subsequently to hypoxia-inducible factor 1α (HIF-1α). The mechanistic study found that SETD5 is an upstream effector of EP300/HIF-1α. SETD5 knockdown reduced the expression of HIF-1α, hexokinase-2, and 6-phosphofructo-2-kinase in the nucleus after treatment with cobalt chloride, a chemical hypoxia mimetic agent that activates HIF-1α to accumulate in the nucleus. Therefore, SETD5 is required for glycolysis in BCSCs through binding to EP300/HIF-1α and could be a potential therapeutic target for breast cancer patients.

Molecular Mechanisms of Cutaneous Squamous Cell Carcinoma

Non-melanoma skin cancers are cutaneous malignancies representing the most common form of cancer in the United States. They are comprised predominantly of basal cell carcinomas and squamous cell carcinomas (cSCC). The incidence of cSCC is increasing, resulting in substantial morbidity and ever higher treatment costs; currently in excess of one billion dollars, per annum. Here, we review research defining the molecular basis and development of cSCC that aims to provide new insights into pathogenesis and drive the development of novel, cost and morbidity saving therapies.

The acetyltransferase p300 is recruited in trans to multiple enhancer sites by lncSmad7

The histone acetyltransferase p300 (also known as KAT3B) is a general transcriptional coactivator that introduces the H3K27ac mark on enhancers triggering their activation and gene transcription. Genome-wide screenings demonstrated that a large fraction of long non-coding RNAs (lncRNAs) plays a role in cellular processes and organ development although the underlying molecular mechanisms remain largely unclear (1,2). We found 122 lncRNAs that interacts directly with p300. In depth analysis of one of these, lncSmad7, is required to maintain ESC self-renewal and it interacts to the C-terminal domain of p300. lncSmad7 also contains predicted RNA-DNA Hoogsteen forming base pairing. Combined Chromatin Isolation by RNA precipitation followed by sequencing (ChIRP-seq) together with CRISPR/Cas9 mutagenesis of the target sites demonstrate that lncSmad7 binds and recruits p300 to enhancers in trans, to trigger enhancer acetylation and transcriptional activation of its target genes. Thus, these results unveil a new mechanism by which p300 is recruited to the genome.

RNA-binding protein p54nrb/NONO potentiates nuclear EGFR-mediated tumorigenesis of triple-negative breast cancer

Nuclear-localized epidermal growth factor receptor (EGFR) highly correlates with the malignant progression and may be a promising therapeutic target for breast cancer. However, molecular mechanisms of nuclear EGFR in triple-negative breast cancer (TNBC) have not been fully elucidated. Here, we performed gene-annotation enrichment analysis for the interactors of nuclear EGFR and found that RNA-binding proteins (RBPs) were closely associated with nuclear EGFR. We further demonstrated p54^nrb/NONO, one of the RBPs, significantly interacted with nuclear EGFR. NONO was upregulated in 80 paired TNBC tissues and indicated a poor prognosis. Furthermore, NONO knockout significantly inhibited TNBC proliferation in vitro and in vivo. Mechanistically, NONO increased the stability of nuclear EGFR and recruited CREB binding protein (CBP) and its accompanying E1A binding protein p300, thereby enhancing the transcriptional activity of EGFR. In turn, EGFR positively regulated the affinity of NONO to mRNAs of nuclear EGFR downstream genes. Furthermore, the results indicated that the nuclear EGFR/NONO complex played a critical role in tumorigenesis and chemotherapy resistance. Taken together, our findings indicate that NONO enhances nuclear EGFR-mediated tumorigenesis and may be a potential therapeutic target for TNBC patients with nuclear EGFR expression.

Understanding p300-transcription factor interactions using sequence variation and hybridization

The hypoxic response is central to cell function and plays a significant role in the growth and survival of solid tumours. HIF-1 regulates the hypoxic response by activating over 100...

Design, Synthesis, and Biological Evaluation of 1-(Indolizin-3-yl)ethan-1-ones as CBP Bromodomain Inhibitors for the Treatment of Prostate Cancer

CREB (cyclic-AMP responsive element binding protein) binding protein (CBP) is a potential target for prostate cancer treatment. Herein, we report the structural optimization of a series of 1-(indolizin-3-yl)ethan-1-one compounds as new selective CBP bromodomain inhibitors, aiming to improve cellular potency and metabolic stability. This process led to compound 9g (Y08284), which possesses good liver microsomal stability and pharmacokinetic properties (F = 25.9%). Furthermore, the compound is able to inhibit CBP bromodomain as well as the proliferation, colony formation, and migration of prostate cancer cells. Additionally, the new inhibitor shows promising antitumor efficacy in a 22Rv1 xenograft model (TGI = 88%). This study provides new lead compounds for further development of drugs for the treatment of prostate cancer.

The pro-angiogenesis effect of miR33a-5p/Ets-1/DKK1 signaling in ox-LDL induced HUVECs

Objective: Angiogenesis is involved in multiple biological processes, including atherosclerosis (AS) and cancer. Dickkopf1 (DKK1) plays many roles in both tumors and AS and has emerged as a potential biomarker of cancer progression and prognosis. Targeting DKK1 is a good choice for oncological treatments. Many anticancer therapies are associated with specific cardiovascular toxicity. However, the effects of DKK1 neutralizing therapy on AS are unclear. We focused on how DKK1 affected angiogenesis in AS and ox-LDL-induced human umbilical vein endothelial cells (HUVECs).

Methods: ApoE-/- mice were fed a high-fat diet and then injected with DKK1i or DKK1 lentivirus to study the effects of DKK1. In vitro, promoter assays, protein analysis, database mining, dual-luciferase reporter assay (DLR), electrophoretic mobility shift assay (EMSA), chromatin immunoprecipitation (ChIP), and coimmunoprecipitation (co-IP) were used to study the mechanism of DKK1 biogenesis. Cell migration and angiogenesis assays were performed to investigate the function and regulatory mechanisms of DKK1.

Results: DKK1 participated in angiogenesis both in the plaques of ApoE-/- mice by knockdown or overexpression of DKK1 and ox-LDL-induced HUVECs. DKK1 induced angiogenesis (increasing migration and capillary formation, inducing expression of VEGFR-2/VEGF-A/MMP) via the CKAP4/PI3K pathway, independent of Wnt/β-catenin. ox-LDL increased the expression and nuclear transfer of Ets-1 and c-jun, and induced the transcriptional activity of DKK1 in HUVECs. Ets-1, along with c-jun and CBP, could bind to the promoter of DKK1 and enhance DKK1 transcription. MiR33a-5p was downregulated in ox-LDL induced HUVECs and aortic artery of high-fat diet ApoE-/- mice. Ets-1 was a direct target of miR33a-5p. MiR33a-5p/Ets-1/ DKK1 axis contributed to angiogenesis.

Conclusions: MiR33a-5p/Ets-1/DKK1 signaling participated in ox-LDL-induced angiogenesis of HUVECs via the CKAP4/PI3K pathway. These new findings provide a rationale and notable method for tumor therapy and cardiovascular protection.

Protein lysine acetylation and its role in different human pathologies: a proteomic approach

INTRODUCTION

Lysine acetylation is a reversible post-translational modification (PTM) regulated through the action of specific types of enzymes: lysine acetyltransferases (KATs) and lysine deacetylases (HDACs), in addition to bromodomains, which are a group of conserved domains which identify acetylated lysine residues, several of the players in the process of protein acetylation, including enzymes and bromodomain-containing proteins, have been related to the progression of several diseases. The combination of high-resolution mass spectrometry-based proteomics, and immunoprecipitation to enrich acetylated peptides has contributed in recent years to expand the knowledge about this PTM described initially in histones and nuclear proteins, and is currently reported in more than 5000 human proteins, that are regulated by this PTM.

AREAS COVERED

This review presents an overview of the main participant elements, the scenario in the development of protein lysine acetylation, and its role in different human pathologies.

EXPERT OPINION

Acetylation targets are practically all cellular processes in eukaryotes and prokaryotes organisms. Consequently, this modification has been linked to many pathologies like cancer, viral infection, obesity, diabetes, cardiovascular, and nervous system-associated diseases, to mention a few relevant examples. Accordingly, some intermediate mediators in the acetylation process have been projected as therapeutic targets.

Interplay between protein acetylation and ubiquitination controls MCL1 protein stability

The anti-apoptotic myeloid cell leukemia 1 (MCL1) protein belongs to the pro-survival BCL2 family and is frequently amplified or elevated in human cancers. MCL1 is highly unstable, with its stability being regulated by phosphorylation and ubiquitination. Here, we identify acetylation as another critical post-translational modification regulating MCL1 protein stability. We demonstrate that the lysine acetyltransferase p300 targets MCL1 at K40 for acetylation, which is counteracted by the deacetylase sirtuin 3 (SIRT3). Mechanistically, acetylation enhances MCL1 interaction with USP9X, resulting in deubiquitination and subsequent MCL1 stabilization. Therefore, ectopic expression of acetylation-mimetic MCL1 promotes apoptosis evasion of cancer cells, enhances colony formation potential, and facilitates xenografted tumor progression. We further demonstrate that elevated MCL1 acetylation sensitizes multiple cancer cells to pharmacological inhibition of USP9X. These findings reveal that acetylation of MCL1 is a critical post-translational modification enhancing its oncogenic function and provide a rationale for developing innovative therapeutic strategies for MCL1-dependent tumors.

MCL1, an anti-apoptotic BCL2 family protein, is frequently overexpressed in a variety of cancers, and its oncogenic function is finely regulated by post-translational modifications such as phosphorylation and ubiquitination. Shimizu et al. dissect the molecular mechanism of acetylation-mediated MCL1 stability control, providing insights into potential therapeutic intervention targeting the MCL1 protein.

Inhibition of CBP synergizes with the RNA-dependent mechanisms of Azacitidine by limiting protein synthesis

The nucleotide analogue azacitidine (AZA) is currently the best treatment option for patients with high-risk myelodysplastic syndromes (MDS). However, only half of treated patients respond and of these almost all eventually relapse. New treatment options are urgently needed to improve the clinical management of these patients. Here, we perform a loss-of-function shRNA screen and identify the histone acetyl transferase and transcriptional co-activator, CREB binding protein (CBP), as a major regulator of AZA sensitivity. Compounds inhibiting the activity of CBP and the closely related p300 synergistically reduce viability of MDS-derived AML cell lines when combined with AZA. Importantly, this effect is specific for the RNA-dependent functions of AZA and not observed with the related compound decitabine that is only incorporated into DNA. The identification of immediate target genes leads us to the unexpected finding that the effect of CBP/p300 inhibition is mediated by globally down regulating protein synthesis.

A Dual-Site Inhibitor of CBP/p300 KIX is a Selective and Effective Modulator of Myb

The protein-protein interaction between the KIX motif of the transcriptional coactivator CBP/p300 and the transcriptional activator Myb is a high-value target due to its established role in certain acute myeloid leukemias (AML) and potential contributions to other cancers. However, the CBP/p300 KIX domain has multiple binding sites, several structural homologues, many binding partners, and substantial conformational plasticity, making it challenging to specifically target using small-molecule inhibitors. Here, we report a picomolar dual-site inhibitor (MybLL-tide) of the Myb-CBP/p300 KIX interaction. MybLL-tide has higher affinity for CBP/p300 KIX than any previously reported compounds while also possessing 5600-fold selectivity for the CBP/p300 KIX domain over other coactivator domains. MybLL-tide blocks the association of CBP and p300 with Myb in the context of the proteome, leading to inhibition of key Myb·KIX-dependent genes in AML cells. These results show that MybLL-tide is an effective, modifiable tool to selectively target the KIX domain and assess transcriptional effects in AML cells and potentially other cancers featuring aberrant Myb behavior. Additionally, the dual-site design has applicability to the other challenging coactivators that bear multiple binding surfaces.

ATF3 promotes the serine synthesis pathway and tumor growth under dietary serine restriction

The serine synthesis pathway (SSP) involving metabolic enzymes phosphoglycerate dehydrogenase (PHGDH), phosphoserine aminotransferase 1 (PSAT1), and phosphoserine phosphatase (PSPH) drives intracellular serine biosynthesis and is indispensable for cancer cells to grow in serine-limiting environments. However, how SSP is regulated is not well understood. Here, we report that activating transcription factor 3 (ATF3) is crucial for transcriptional activation of SSP upon serine deprivation. ATF3 is rapidly induced by serine deprivation via a mechanism dependent on ATF4, which in turn binds to ATF4 and increases the stability of this master regulator of SSP. ATF3 also binds to the enhancers/promoters of PHGDH, PSAT1, and PSPH and recruits p300 to promote expression of these SSP genes. As a result, loss of ATF3 expression impairs serine biosynthesis and the growth of cancer cells in the serine-deprived medium or in mice fed with a serine/glycine-free diet. Interestingly, ATF3 expression positively correlates with PHGDH expression in a subset of TCGA cancer samples.

Activation of the serine synthesis pathway is important for cancer cell growth, but how this pathway is regulated is not well understood. Li et al. report that ATF3 is an important regulator of this pathway and can promote serine biosynthesis and tumor growth under serine-limiting conditions.

Genetic and clinical heterogeneity in Korean patients with Rubinstein-Taybi syndrome

Background

Rubinstein–Taybi syndrome (RSTS) is a rare congenital malformation syndrome with clinical characteristics such as hypertrichosis, high arched eyebrows, large beaked nose, and broad thumbs and halluces. RSTS patients showed intellectual disability and health problems such as short stature, ophthalmologic abnormalities, congenital heart defects, genitourinary defects, and variable types of tumors. Although mutations in CREBBP and EP300 genes are associated with RSTS features, genetic causation is still unknown in 30% of patients.

Methods

We present clinical and molecular genetic characteristics of 25 unrelated Korean patients clinically diagnosed with RSTS. Sanger sequencing analysis and multiplex ligation‐dependent probe amplification for CREBBP in 25 patients and exome sequencing of CREBBP‐negative cases were performed in nine patients successively.

Results

Causative variants were identified in 20 (80%) patients: 16 (64%) in CREBBP and 4 (16%) in EP300. All the identified variants predict protein truncation (11 frameshift, 2 nonsense, 1 splicing‐site, and 6 large intragenic deletions); there are no repeatedly identified sequence variants. Four of the CREBBP and all four EP300 variants are novel. Intellectual disability was noted in 24/25 patients (96%); no difference was found between CREBBP and EP300 groups. One patient with a CREBBP variant (4%) had malignant tumor.

Conclusions

To date, this is the largest cohort of patients with RSTS including EP300‐related patients in Korea. Future large‐scale studies to find genetic mutation of molecularly unsolved patients and long‐term prospective studies are required to validate our results.

Current Insights and Advancements in Head and Neck Cancer: Emerging Biomarkers and Therapeutics with Cues from Single Cell and 3D Model Omics Profiling

Head and neck cancer (HNC) is among the ten leading malignancies worldwide, with India solely contributing one-third of global oral cancer cases. The current focus of all cutting-edge strategies against this global malignancy are directed towards the heterogeneous tumor microenvironment that obstructs most treatment blueprints. Subsequent to the portrayal of established information, the review details the application of single cell technology, organoids and spheroid technology in relevance to head and neck cancer and the tumor microenvironment acknowledging the resistance pattern of the heterogeneous cell population in HNC. Bioinformatic tools are used for study of differentially expressed genes and further omics data analysis. However, these tools have several challenges and limitations when analyzing single-cell gene expression data that are discussed briefly. The review further examines the omics of HNC, through comprehensive analyses of genomics, transcriptomics, proteomics, metabolomics, and epigenomics profiles. Patterns of alterations vary between patients, thus heterogeneity and molecular alterations between patients have driven the clinical significance of molecular targeted therapies. The analyses of potential molecular targets in HNC are discussed with connotation to the alteration of key pathways in HNC followed by a comprehensive study of protein kinases as novel drug targets including its ATPase and additional binding pockets, non-catalytic domains and single residues. We herein review, the therapeutic agents targeting the potential biomarkers in light of new molecular targeted therapies. In the final analysis, this review suggests that the development of improved target-specific personalized therapies can combat HNC's global plight.

Hypoxia-Inducible Factor (HIF): Fuel for Cancer Progression

Hypoxia is an integral part of the tumor microenvironment, caused primarily due to rapidly multiplying tumor cells and a lack of proper blood supply. Among the major hypoxic pathways, HIF-1 transcription factor activation is one of the widely investigated pathways in the hypoxic tumor microenvironment (TME). HIF-1 is known to activate several adaptive reactions in response to oxygen deficiency in tumor cells. HIF-1 has two subunits, HIF-1β (constitutive) and HIF-1α (inducible). The HIF-1α expression is largely regulated via various cytokines (through PI3K-ACT-mTOR signals), which involves the cascading of several growth factors and oncogenic cascades. These events lead to the loss of cellular tumor suppressant activity through changes in the level of oxygen via oxygen-dependent and oxygen-independent pathways. The significant and crucial role of HIF in cancer progression and its underlying mechanisms have gained much attention lately among the translational researchers in the fields of cancer and biological sciences, which have enabled them to correlate these mechanisms with various other disease modalities. In the present review, we have summarized the key findings related to the role of HIF in the progression of tumors.

A genetic screen in Drosophila uncovers the multifaceted properties of the NUP98-HOXA9 oncogene

Acute myeloid leukemia (AML) underlies the uncontrolled accumulation of immature myeloid blasts. Several cytogenetic abnormalities have been associated with AML. Among these is the NUP98-HOXA9 (NA9) translocation that fuses the Phe-Gly repeats of nucleoporin NUP98 to the homeodomain of the transcription factor HOXA9. The mechanisms enabling NA9-induced leukemia are poorly understood. Here, we conducted a genetic screen in Drosophila for modifiers of NA9. The screen uncovered 29 complementation groups, including genes with mammalian homologs known to impinge on NA9 activity. Markedly, the modifiers encompassed a diversity of functional categories, suggesting that NA9 perturbs multiple intracellular events. Unexpectedly, we discovered that NA9 promotes cell fate transdetermination and that this phenomenon is greatly influenced by NA9 modifiers involved in epigenetic regulation. Together, our work reveals a network of genes functionally connected to NA9 that not only provides insights into its mechanism of action, but also represents potential therapeutic targets.

Acute myeloid leukemia or AML is a cancer of blood cells. Despite significant progress in recent years, a majority of afflicted individuals still succumbs to the disease. A variety of genetic defects have been associated to AML. Among these are chromosomal translocations, which entail the fusion of two genes, leading to the production of cancer-inducing chimeric proteins. A representative example is the NUP98-HOXA9 oncoprotein, which results from the fusion of the NUP98 and HOXA9 genes. The mechanism of action of NUP98-HOXA9 remains poorly understood. Given the evolutionarily conservation of NUP98 and HOXA9 as well as basic cellular processes across multicellular organisms, we took advantage of Drosophila fruit flies as a genetic tool to identify genes that impinge on the activity of human NUP98-HOXA9. Surprisingly, this approach identified a relatively large spectrum of conserved genes that engaged in functional interplay with NUP98-HOXA9, which indicated the pervasive effects that this oncogene has on basic cellular events. While some genes have been previously linked to NUP98-HOXA9, thus validating our experimental approach, several others are novel and as such represent potentially new avenues for therapeutic intervention.

Role of Virus-Induced Host Cell Epigenetic Changes in Cancer

The tumor viruses human T-lymphotropic virus 1 (HTLV-1), hepatitis C virus (HCV), Merkel cell polyomavirus (MCPyV), high-risk human papillomaviruses (HR-HPVs), Epstein-Barr virus (EBV), Kaposi’s sarcoma-associated herpes virus (KSHV) and hepatitis B virus (HBV) account for approximately 15% of all human cancers. Although the oncoproteins of these tumor viruses display no sequence similarity to one another, they use the same mechanisms to convey cancer hallmarks on the infected cell. Perturbed gene expression is one of the underlying mechanisms to induce cancer hallmarks. Epigenetic processes, including DNA methylation, histone modification and chromatin remodeling, microRNA, long noncoding RNA, and circular RNA affect gene expression without introducing changes in the DNA sequence. Increasing evidence demonstrates that oncoviruses cause epigenetic modifications, which play a pivotal role in carcinogenesis. In this review, recent advances in the role of host cell epigenetic changes in virus-induced cancers are summarized.

Relationship between the structure and function of the transcriptional regulator E2A

E proteins are transcriptional regulators that regulate many developmental processes in animals and lymphocytosis and leukemia in Homo sapiens. In particular, E2A, a member of the E protein family, plays a major role in the transcriptional regulatory network that promotes the differentiation and development of B and T lymphocytes. E2A-mediated transcriptional regulation usually requires the formation of E2A dimers, which then bind to coregulators. In this review, we summarize the mechanisms by which E2A participates in transcriptional regulation from a structural perspective. More specifically, the C-terminal helix-loop-helix (HLH) region of the basic HLH (bHLH) domain first dimerizes, and then the activation domains of E2A bind to different coactivators or corepressors in different cell contexts, resulting in histone acetylation or deacetylation, respectively. Then, the N-terminal basic region (b) of the bHLH domain binds to or dissociates from a specific DNA motif (E-box sequence). Last, trans-activation or trans-repression occurs. We also summarize the properties of these E2A domains and their interactions with the domains of other proteins. The feasibility of developing drugs based on these domains is discussed.

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.

CBP/p300: Critical Co-Activators for Nuclear Steroid Hormone Receptors and Emerging Therapeutic Targets in Prostate and Breast Cancers

The CREB-binding protein (CBP) and p300 are two paralogous lysine acetyltransferases (KATs) that were discovered in the 1980s-1990s. Since their discovery, CBP/p300 have emerged as important regulatory proteins due to their ability to acetylate histone and non-histone proteins to modulate transcription. Work in the last 20 years has firmly established CBP/p300 as critical regulators for nuclear hormone signaling pathways, which drive tumor growth in several cancer types. Indeed, CBP/p300 are critical co-activators for the androgen receptor (AR) and estrogen receptor (ER) signaling in prostate and breast cancer, respectively. The AR and ER are stimulated by sex hormones and function as transcription factors to regulate genes involved in cell cycle progression, metabolism, and other cellular functions that contribute to oncogenesis. Recent structural studies of the AR/p300 and ER/p300 complexes have provided critical insights into the mechanism by which p300 interacts with and activates AR- and ER-mediated transcription. Breast and prostate cancer rank the first and forth respectively in cancer diagnoses worldwide and effective treatments are urgently needed. Recent efforts have identified specific and potent CBP/p300 inhibitors that target the acetyltransferase activity and the acetytllysine-binding bromodomain (BD) of CBP/p300. These compounds inhibit AR signaling and tumor growth in prostate cancer. CBP/p300 inhibitors may also be applicable for treating breast and other hormone-dependent cancers. Here we provide an in-depth account of the critical roles of CBP/p300 in regulating the AR and ER signaling pathways and discuss the potential of CBP/p300 inhibitors for treating prostate and breast cancer.