The KDM5A/RBP2 histone demethylase represses NOTCH signaling to sustain neuroendocrine differentiation and promote small cell lung cancer tumorigenesis.

More than 90% of small cell lung cancers (SCLCs) harbor loss-of-function mutations in the tumor suppressor gene RB1 The canonical function of the RB1 gene product, pRB, is to repress the E2F transcription factor family, but pRB also functions to regulate cellular differentiation in part through its binding to the histone demethylase KDM5A (also known as RBP2 or JARID1A). We show that KDM5A promotes SCLC proliferation and SCLC's neuroendocrine differentiation phenotype in part by sustaining expression of the neuroendocrine transcription factor ASCL1. Mechanistically, we found that KDM5A sustains ASCL1 levels and neuroendocrine differentiation by repressing NOTCH2 and NOTCH target genes. To test the role of KDM5A in SCLC tumorigenesis in vivo, we developed a CRISPR/Cas9-based mouse model of SCLC by delivering an adenovirus (or an adeno-associated virus [AAV]) that expresses Cre recombinase and sgRNAs targeting Rb1, Tp53, and Rbl2 into the lungs of Lox-Stop-Lox Cas9 mice. Coinclusion of a KDM5A sgRNA decreased SCLC tumorigenesis and metastasis, and the SCLCs that formed despite the absence of KDM5A had higher NOTCH activity compared to KDM5A+/+ SCLCs. This work establishes a role for KDM5A in SCLC tumorigenesis and suggests that KDM5 inhibitors should be explored as treatments for SCLC.

RepID represses megakaryocytic differentiation by recruiting CRL4A-JARID1A at DAB2 promoter.

BACKGROUND: Megakaryocytes (MKs) are platelet precursors, which arise from hematopoietic stem cells (HSCs). While MK lineage commitment and differentiation are accompanied by changes in gene expression, many factors that modulate megakaryopoiesis remain to be uncovered. Replication initiation determinant protein (RepID) which has multiple histone-code reader including bromodomain, cryptic Tudor domain and WD40 domains and Cullin 4-RING E3 ubiquitin ligase complex (CRL4) recruited to chromatin mediated by RepID have potential roles in gene expression changes via epigenetic regulations. We aimed to investigate whether RepID-CRL4 participates in transcriptional changes required for MK differentiation. METHODS: The PCR array was performed using cDNAs derived from RepID-proficient or RepID-deficient K562 erythroleukemia cell lines. Correlation between RepID and DAB2 expression was examined in the Cancer Cell Line Encyclopedia (CCLE) through the CellMinerCDB portal. The acceleration of MK differentiation in RepID-deficient K562 cells was determined by estimating cell sizes as well as counting multinucleated cells known as MK phenotypes, and by qRT-PCR analysis to validate transcripts of MK markers using phorbol 12-myristate 13-acetate (PMA)-mediated MK differentiation condition. Interaction between CRL4 and histone methylation modifying enzymes were investigated using BioGRID database, immunoprecipitation and proximity ligation assay. Alterations of expression and chromatin binding affinities of RepID, CRL4 and histone methylation modifying enzymes were investigated using subcellular fractionation followed by immunoblotting. RepID-CRL4-JARID1A-based epigenetic changes on DAB2 promoter were analyzed by chromatin-immunoprecipitation and qPCR analysis. RESULTS: RepID-deficient K562 cells highly expressing MK markers showed accelerated MKs differentiation exhibiting increases in cell size, lobulated nuclei together with reaching maximum levels of MK marker expression earlier than RepID-proficient K562 cells. Recovery of WD40 domain-containing RepID constructs in RepID-deficient background repressed DAB2 expression. CRL4A formed complex with histone H3K4 demethylase JARID1A in soluble nucleus and loaded to the DAB2 promoter in a RepID-dependent manner during proliferation condition. RepID, CRL4A, and JARID1A were dissociated from the chromatin during MK differentiation, leading to euchromatinization of the DAB2 promoter. CONCLUSION: This study uncovered a role for the RepID-CRL4A-JARID1A pathway in the regulation of gene expression for MK differentiation, which can form the basis for the new therapeutic approaches to induce platelet production. Video Abstract.

Autochthonous tumors driven by Rb1 loss have an ongoing requirement for the RBP2 histone demethylase.

Inactivation of the retinoblastoma gene (RB1) product, pRB, is common in many human cancers. Targeting downstream effectors of pRB that are central to tumorigenesis is a promising strategy to block the growth of tumors harboring loss-of-function RB1 mutations. One such effector is retinoblastoma-binding protein 2 (RBP2, also called JARID1A or KDM5A), which encodes an H3K4 demethylase. Binding of pRB to RBP2 has been linked to the ability of pRB to promote senescence and differentiation. Importantly, genetic ablation of RBP2 is sufficient to phenocopy pRB's ability to induce these cellular changes in cell culture experiments. Moreover, germline Rbp2 deletion significantly impedes tumorigenesis in Rb1+/- mice. The value of RBP2 as a therapeutic target in cancer, however, hinges on whether loss of RBP2 could block the growth of established tumors as opposed to simply delaying their onset. Here we show that conditional, systemic ablation of RBP2 in tumor-bearing Rb1+/- mice is sufficient to slow tumor growth and significantly extend survival without causing obvious toxicity to the host. These findings show that established Rb1-null tumors require RBP2 for growth and further credential RBP2 as a therapeutic target in human cancers driven by RB1 inactivation.

Computationally predicted SARS-COV-2 encoded microRNAs target NFKB, JAK/STAT and TGFB signaling pathways.

Recently an outbreak that emerged in Wuhan, China in December 2019, spread to the whole world in a short time and killed >1,410,000 people. It was determined that a new type of beta coronavirus called severe acute respiratory disease coronavirus type 2 (SARS-CoV-2) was causative agent of this outbreak and the disease caused by the virus was named as coronavirus disease 19 (COVID19). Despite the information obtained from the viral genome structure, many aspects of the virus-host interactions during infection is still unknown. In this study we aimed to identify SARS-CoV-2 encoded microRNAs and their cellular targets. We applied a computational method to predict miRNAs encoded by SARS-CoV-2 along with their putative targets in humans. Targets of predicted miRNAs were clustered into groups based on their biological processes, molecular function, and cellular compartments using GO and PANTHER. By using KEGG pathway enrichment analysis top pathways were identified. Finally, we have constructed an integrative pathway network analysis with target genes. We identified 40 SARS-CoV-2 miRNAs and their regulated targets. Our analysis showed that targeted genes including NFKB1, NFKBIE, JAK1-2, STAT3-4, STAT5B, STAT6, SOCS1-6, IL2, IL8, IL10, IL17, TGFBR1-2, SMAD2-4, HDAC1-6 and JARID1A-C, JARID2 play important roles in NFKB, JAK/STAT and TGFB signaling pathways as well as cells' epigenetic regulation pathways. Our results may help to understand virus-host interaction and the role of viral miRNAs during SARS-CoV-2 infection. As there is no current drug and effective treatment available for COVID19, it may also help to develop new treatment strategies.

JARID1a Ablation in the Liver Alters Systemic Metabolism and Adaptation to Feeding.

The liver is a key regulator of systemic energy homeostasis whose proper function is dependent on the circadian clock. Here, we show that livers deficient in the oscillator component JARID1a exhibit a dysregulation of genes involved in energy metabolism. Importantly, we find that mice that lack hepatic JARID1a have decreased lean body mass, decreased respiratory exchange ratios, faster production of ketones, and increased glucose production in response to fasting. Finally, we find that JARID1a loss compromises the response of the hepatic transcriptome to nutrient availability. In all, ablation of hepatic JARID1a disrupts the coordination of hepatic metabolic programs with whole-body consequences.

JARID1 Histone Demethylases: Emerging Targets in Cancer.

JARID1 proteins are histone demethylases that both regulate normal cell fates during development and contribute to the epigenetic plasticity that underlies malignant transformation. This H3K4 demethylase family participates in multiple repressive transcriptional complexes at promoters and has broader regulatory effects on chromatin that remain ill-defined. There is growing understanding of the oncogenic and tumor suppressive functions of JARID1 proteins, which are contingent on cell context and the protein isoform. Their contributions to stem cell-like dedifferentiation, tumor aggressiveness, and therapy resistance in cancer have sustained interest in the development of JARID1 inhibitors. Here we review the diverse and context-specific functions of the JARID1 proteins that may impact the utilization of emerging targeted inhibitors of this histone demethylase family in cancer therapy.