Loss of LOXL2 Promotes Uterine Hypertrophy and Tumor Progression by Enhancing H3K36ac-Dependent Gene Expression.

Lysyl oxidase-like 2 (LOXL2) is a member of the scavenger receptor cysteine-rich (SRCR) repeat carrying LOX family. Although LOXL2 is suspected to be involved in histone association and chromatin modification, the role of LOXL2 in epigenetic regulation during tumorigenesis and cancer progression remains unclear. Here, we report that nuclear LOXL2 associates with histone H3 and catalyzes H3K36ac deacetylation and deacetylimination. Both the N-terminal SRCR repeats and the C-terminal catalytic domain of LOXL2 carry redundant deacetylase catalytic activity. Overexpression of LOXL2 markedly reduced H3K36 acetylation and blocked H3K36ac-dependent transcription of genes, including c-MYC, CCND1, HIF1A, and CD44. Consequently, LOXL2 overexpression reduced cancer cell proliferation in vitro and inhibited xenograft tumor growth in vivo. In contrast, LOXL2 deficiency resulted in increased H3K36 acetylation and aberrant expression of H3K36ac-dependent genes involved in multiple oncogenic signaling pathways. Female LOXL2-deficient mice spontaneously developed uterine hypertrophy and uterine carcinoma. Moreover, silencing LOXL2 in cancer cells enhanced tumor progression and reduced the efficacy of cisplatin and anti-programmed cell death 1 (PD-1) combination therapy. Clinically, low nuclear LOXL2 expression and high H3K36ac levels corresponded to poor prognosis in uterine endometrial carcinoma patients. These results suggest that nuclear LOXL2 restricts cancer development in the female reproductive system via the regulation of H3K36ac deacetylation. SIGNIFICANCE: LOXL2 loss reprograms the epigenetic landscape to promote uterine cancer initiation and progression and repress the efficacy of anti-PD-1 immunotherapy, indicating that LOXL2 is a tumor suppressor.

Synthesis and characterization of arabinoxylan-bis[2-(methacryloyloxy)ethyl] phosphate crosslinked copolymer network by high energy gamma radiation for use in controlled drug delivery applications.

Keeping in view the therapeutic important dietary fiber psyllium, herein this research report its potential has been explored for the formation of sterile hydrogel by high energy radiation induced copolymerization of arabinoxylan-poly bis[2-(methacryloyloxy)ethyl] phosphate (BMEP) for use as drug delivery carrier. The polymeric network structure was characterized by 13C NMR, FTIR, TGA/DTG and DSC, XRD and AFM techniques. Release profile of a drug cefuroxime and best fit kinetic model were determined. The blood -polymer interaction, mucosal-polymer adhesion, antioxidant and mechanical properties were also evaluated. The radiation dose influenced the crosslink density and the mesh size of the hydrogel network. Release profile of a drug cefuroxime followed non-Fickian diffusion and best fitted to first order kinetic model. The grafted product was sterile, porous, antioxidant and mucoadhesive in nature and could be explored for controlled and sustained GIT drug delivery applications.

K63-linked ubiquitination of DYRK1A by TRAF2 alleviates Sprouty 2-mediated degradation of EGFR.

Dual specificity tyrosine phosphorylation regulated kinase 1A, DYRK1A, functions in multiple cellular pathways, including signaling, endocytosis, synaptic transmission, and transcription. Alterations in dosage of DYRK1A leads to defects in neurogenesis, cell growth, and differentiation, and may increase the risk of certain cancers. DYRK1A localizes to a number of subcellular structures including vesicles where it is known to phosphorylate a number of proteins and regulate vesicle biology. However, the mechanism by which it translocates to vesicles is poorly understood. Here we report the discovery of TRAF2, an E3 ligase, as an interaction partner of DYRK1A. Our data suggest that TRAF2 binds to PVQE motif residing in between the PEST and histidine repeat domain (HRD) of DYRK1A protein, and mediates K63-linked ubiquitination of DYRK1A. This results in translocation of DYRK1A to the vesicle membrane. DYRK1A increases phosphorylation of Sprouty 2 on vesicles, leading to the inhibition of EGFR degradation, and depletion of TRAF2 expression accelerates EGFR degradation. Further, silencing of DYRK1A inhibits the growth of glioma cells mediated by TRAF2. Collectively, these findings suggest that the axis of TRAF2-DYRK1A-Sprouty 2 can be a target for new therapeutic development for EGFR-mediated human pathologies.

SNP rs17079281 decreases lung cancer risk through creating an YY1-binding site to suppress DCBLD1 expression.

Genome-wide association studies (GWAS) have identified numerous genetic variants that are associated with lung cancer risk, but the biological mechanisms underlying these associations remain largely unknown. Here we investigated the functional relevance of a genetic region in 6q22.2 which was identified to be associated with lung cancer risk in our previous GWAS. We performed linkage disequilibrium (LD) analysis and bioinformatic prediction to screen functional SNPs linked to a tagSNP in 6q22.2 loci, followed by two case-control studies and a meta-analysis with 4403 cases and 5336 controls to identify if these functional SNPs were associated with lung cancer risk. A novel SNP rs17079281 in the DCBLD1 promoter was identified to be associated with lung cancer risk in Chinese populations. Compared with those with C allele, patients with T allele had lower risk of adenocarcinoma (adjusted OR = 0.86; 95% CI: 0.80-0.92), but not squamous cell carcinoma (adjusted OR = 0.99; 95% CI: 0.91-1.10), and patients with the C/T or T/T genotype had lower levels of DCBLD1 expression than those with C/C genotype in lung adenocarcinoma tissues. We performed functional assays to characterize its biological relevance. The results showed that the T allele of rs17079281 had higher binding affinity to transcription factor YY1 than the C allele, which suppressed DCBLD1 expression. DCBLD1 behaved like an oncogene, promoting tumor growth by influencing cell cycle progression. These findings suggest that the functional variant rs17079281C>T decreased lung adenocarcinoma risk by creating an YY1-binding site to suppress DCBLD1 expression, which may serve as a biomarker for assessing lung cancer susceptibility.

Genome-wide CRISPR screen identifies ELP5 as a determinant of gemcitabine sensitivity in gallbladder cancer.

Gemcitabine is the first-line treatment for locally advanced and metastatic gallbladder cancer (GBC), but poor gemcitabine response is universal. Here, we utilize a genome-wide CRISPR screen to identify that loss of ELP5 reduces the gemcitabine-induced apoptosis in GBC cells in a P53-dependent manner through the Elongator complex and other uridine 34 (U34) tRNA-modifying enzymes. Mechanistically, loss of ELP5 impairs the integrity and stability of the Elongator complex to abrogate wobble U34 tRNA modification, and directly impedes the wobble U34 modification-dependent translation of hnRNPQ mRNA, a validated P53 internal ribosomal entry site (IRES) trans-acting factor. Downregulated hnRNPQ is unable to drive P53 IRES-dependent translation, but rescuing a U34 modification-independent hnRNPQ mutant could restore P53 translation and gemcitabine sensitivity in ELP5-depleted GBC cells. GBC patients with lower ELP5, hnRNPQ, or P53 expression have poor survival outcomes after gemcitabine chemotherapy. These results indicate that the Elongator/hnRNPQ/P53 axis controls gemcitabine sensitivity in GBC cells.

PLEK2 promotes gallbladder cancer invasion and metastasis through EGFR/CCL2 pathway.

BACKGROUND: Gallbladder cancer (GBC) is an extremely malignant tumor with a high mortality rate. Little is known about its invasion and metastasis mechanism so far. METHODS: To identify the driver genes in GBC metastasis, we performed a mRNA microarray of metastatic GBC and paired non-tumor samples, and found PLEK2 was markedly upregulated in GBC tissues. Next, the expression of PLEK2 in GBC were examined in a larger cohort of patients by qRT-PCR, western blot and IHC staining. The clinicopathologic correlation of PLEK2 was determined by statistical analyses. The biological involvement of PLEK2 in GBC metastasis and the underlying mechanisms were investigated. RESULTS: In this study, we found that PLEK2 had higher expression in GBC tumor tissues compared to non-cancerous adjacent tissues and cholecystolithiasis tissues. The clinicopathologic analyses showed PLEK2 expression was positively correlated with tumor TNM stage, distant metastasis and PLEK2 was an independent predictor of overall survival (OS) in GBC patients. The cellular function assays showed PLEK2 promoted GBC cells migration, invasion and liver metastasis in mouse model via the regulation of epithelial-mesenchymal transition (EMT) process. Our mass spectrum and co-immunoprecipitation (co-IP) assays demonstrated that PLEK2 could interact with the kinase domain of EGFR and suppress EGFR ubiquitination mediated by c-CBL, leading to constitutive activation of EGFR signaling. Furthermore, RNA-sequencing and qRT-PCR results demonstrated chemokine (C-C motif) ligand 2 (CCL2), a target gene downstream of PLEK2/EGFR signaling, mediated the motility-promoting function of PLEK2. CONCLUSIONS: On the basis of these collective data, we propose that PLEK2 promotes the invasion and metastasis of GBC by EGFR/CCL2 pathway and PLEK2 can serve as a potential therapeutic target for GBC treatment.

DYRK1A interacts with histone acetyl transferase p300 and CBP and localizes to enhancers.

DYRK1A, dual-specificity tyrosine phosphorylation-regulated kinase 1A, which is linked to mental retardation and microcephaly, is a member of the CMGC group of kinases. It has both cytoplasmic and nuclear functions, however, molecular mechanisms of how DYRK1A regulates gene expression is not well understood. Here, we identify two histone acetyltransferases, p300 and CBP, as interaction partners of DYRK1A through a proteomics study. We show that overexpression of DYKR1A causes hyperphosphorylation of p300 and CBP. Using genome-wide location (ChIP-sequencing) analysis of DYRK1A, we show that most of the DYRK1A peaks co-localize with p300 and CBP, at enhancers or near the transcription start sites (TSS). Modulation of DYRK1A, by shRNA mediated reduction or transfection mediated overexpression, leads to alteration of expression of downstream located genes. We show that the knockdown of DYRK1A results in a significant loss of H3K27acetylation at these enhancers, suggesting that DYRK1A modulates the activity of p300/CBP at these enhancers. We propose that DYRK1A functions in enhancer regulation by interacting with p300/CBP and modulating their activity. Overall, DYRK1A function in the regulation of enhancer activity provides a new mechanistic understanding of DYRK1A mediated regulation of gene expression, which may help in better understanding of the roles of DYRK1A in human pathologies.

miR-92b-3p acts as a tumor suppressor by targeting Gabra3 in pancreatic cancer.

BACKGROUND: MicroRNAs (miRNAs) can act as oncogenes or tumor suppressors by controlling cell proliferation, differentiation, metastasis and apoptosis, and miRNA dysregulation is involved in the development of pancreatic cancer (PC). Our previous study demonstrated that Gabra3 plays critical roles in cancer progression. However, whether Gabra3 is regulated by miRNAs in PC remains unknown. METHODS: The expression levels of miR-92b-3p and Gabra3 were measured by quantitative PCR (qPCR), immunoblotting, in situ hybridization (ISH) and immunohistochemistry (IHC). The proliferation rate of PC cells was detected by MTS assay. Wound-healing and transwell assays were used to examine the invasive abilities of PC cells. Dual-luciferase reporter assays were used to determine how miR-92b-3p regulates Gabra3. Xenograft mouse models were used to assess the role of miR-92b-3p in PC tumor formation in vivo. RESULTS: Here, we provide evidence that miR-92b-3p acted as a tumor suppressor in PC by regulating Gabra3 expression. MiR-92b-3p expression levels were lower in PC tissues than corresponding noncancerous pancreatic (CNP) tissues and were associated with a poor prognosis in PC patients. MiR-92b-3p overexpression suppressed the proliferation and invasion of PC cells in both in vivo and in vitro models. Conversely, miR-92b-3p knockdown induced an aggressive phenotype in PC cells. Mechanistically, miR-92b-3p overexpression suppressed Gabra3 expression, which then led to the inactivation of important oncogenic pathways, including the AKT/mTOR and JNK pathways. CONCLUSION: Our results suggest that miR-92b-3p acted as a tumor suppressor by targeting Gabra3-associated oncogenic pathways; these results provide novel insight into future treatments for PC patients.

MiR-143-5p Deficiency Triggers EMT and Metastasis by Targeting HIF-1α in Gallbladder Cancer.

BACKGROUND/AIMS: Early metastasis plays a pivotal role in tumor-caused death in gallbladder cancer (GBC) patients. Increasing evidence suggest that miR-143-5p is an active player involved in cancer metastasis and a potential therapeutic target. However, its role in the development of GBC cells remains unclear. The aim of this study is to reveal the inhibiting effects of miR-143-5p on the proliferation and metastasis in GBC. METHODS: Quantitative real-time PCR were used to investigate miR-143-5p and its target HIF-1α mRNA levels. Protein expression was measured by immunohistochemistry and western blot. The function and regulation mechanism of miR-143-5p was confirmed by MTS, colony formation, wound healing, transwell, and luciferase reporter assays. RESULTS: miR-143-5p was first found significantly reduced in GBC tissues compared with corresponding noncancerous gallbladder tissues. In addition, miR-143-5p deficiency correlated well with larger tumor size, advanced TNM stage, and poorer survival rate. In vitro, miR-143-5p addition dramatically suppressed GBC cells proliferation, migration and invasion, whereas miR-143-5p antisense led the opposite effects. Further elucidating the molecular mechanism inside, we found miR-143-5p exerted its inhibitory function through downregulating the expression of HIF-1α, which further reduced Twist1 and impeded epithelial-mesenchymal transition (EMT). CONCLUSIONS: Altogether, our studies identified a novel regulator, miR-143-5p, implicated in GBC prognosis through targeting HIF-1α/EMT related signaling pathway, which could serve as a biomarker and therapeutic target for GBC.

miR-218-5p restores sensitivity to gemcitabine through PRKCE/MDR1 axis in gallbladder cancer.

Gallbladder cancer (GBC) is one of the most common malignancy of the biliary tract characterized by its high chemoresistant tendency. Although great progresses have been made in recent decades for treating many cancers with anticancer drugs, effective therapeutics methods for anti-GBC are still lacking. Therefore, investigations into identifying the mechanisms underlying the drug resistance of GBC are greatly needed. In this study, we show that miR-218-5p plays a critical role in gemcitabine resistance of GBC. miR-218-5p levels were significantly lower in GBC than adjacent non-cancer tissues, and which were also associated with patient prognosis. While miR-218-5p overexpression abrogated gemcitabine resistance of GBC cells, silencing of which exhibited the opposite effects. Via six microRNA targets prediction algorithms, we found that PRKCE is a potential target of miR-218-5p. Moreover, miR-218-5p overexpression repressed the luciferase activity of reporter constructs containing 3'-UTR of PRKCE and also reduced PRKCE expression. Further studies revealed that miR-218-5p promotes sensitivity of gemcitabine by abolishing PRKCE-induced upregulation of MDR1/P-gp. Taken together, our results imply that an intimate correlation between miR-218-5p and PRKCE/MDR1 axis abnormal expression is a key determinant of gemcitabine tolerance, and suggest a novel miR-218-5p-based clinical intervention target for GBC patients.

DOT1L-long enhances breast cancer metastasis / 上海交通大学学报（医学版）

Objective · To investigate the histone methyltransferase capability of DOT1L-long form and its role in breast cancer metastasis.Methods · The existence of DOT1L-long form was confirmed by PCR, and the mRNA level of DOT1L was tested by real-time PCR. In HEK293T cells in which DOT1L canonical and DOT1L-long were overexpressed respectively, Western blotting was used to test the expression level of DOT1L and the histone methyltransferase capability. In the MCF10A cell line with inducible expression of DOT1L-long, real-time PCR was used to detect the mRNA level of epithelial-mesenchymal transition (EMT) marker, and transwell assay was used to detect the migration of breast cancer cells in which the expression level of DOT1L is low or high. Results · PCR demonstrated the existence of DOT1L-long form, and real-time PCR showed it widely exists in HCT116, T98G, MCF10A cells, etc. Western blotting showed the expression of DOT1L-long form and its H3K79 methyltransferase activity. In MCF10A cells in which overexpressed canonical DOT1L and DOT1L-long, mRNA levels of N-cadherin and fibronectine increased. Transwell showed canonical DOT1L and DOT1L-long both substantially increased the migration of breast cancer cells. Conclusion · The existence of DOT1L-long was confirmed and investigated, which is 202 amino acids longer than the canonical DOT1L, and is coded by a new exon, located between exon 27 and 28. Further, the DOT1L-long has H3K79 methyltransferase activity, and is able to promote breast cancer metastasis.

DOT1L-long enhances breast cancer metastasis / 上海交通大学学报（医学版）

Objective · To investigate the histone methyltransferase capability of DOT1L-long form and its role in breast cancer metastasis.Methods · The existence of DOT1L-long form was confirmed by PCR, and the mRNA level of DOT1L was tested by real-time PCR. In HEK293T cells in which DOT1L canonical and DOT1L-long were overexpressed respectively, Western blotting was used to test the expression level of DOT1L and the histone methyltransferase capability. In the MCF10A cell line with inducible expression of DOT1L-long, real-time PCR was used to detect the mRNA level of epithelial-mesenchymal transition (EMT) marker, and transwell assay was used to detect the migration of breast cancer cells in which the expression level of DOT1L is low or high. Results · PCR demonstrated the existence of DOT1L-long form, and real-time PCR showed it widely exists in HCT116, T98G, MCF10A cells, etc. Western blotting showed the expression of DOT1L-long form and its H3K79 methyltransferase activity. In MCF10A cells in which overexpressed canonical DOT1L and DOT1L-long, mRNA levels of N-cadherin and fibronectine increased. Transwell showed canonical DOT1L and DOT1L-long both substantially increased the migration of breast cancer cells. Conclusion · The existence of DOT1L-long was confirmed and investigated, which is 202 amino acids longer than the canonical DOT1L, and is coded by a new exon, located between exon 27 and 28. Further, the DOT1L-long has H3K79 methyltransferase activity, and is able to promote breast cancer metastasis.

An Evolutionary Conserved Epigenetic Mark of Polycomb Response Elements Implemented by Trx/MLL/COMPASS.

Polycomb response elements (PREs) are specific DNA sequences that stably maintain the developmental pattern of gene expression. Drosophila PREs are well characterized, whereas the existence of PREs in mammals remains debated. Accumulating evidence supports a model in which CpG islands recruit Polycomb group (PcG) complexes; however, which subset of CGIs is selected to serve as PREs is unclear. Trithorax (Trx) positively regulates gene expression in Drosophila and co-occupies PREs to antagonize Polycomb-dependent silencing. Here we demonstrate that Trx-dependent H3K4 dimethylation (H3K4me2) marks Drosophila PREs and maintains the developmental expression pattern of nearby genes. Similarly, the mammalian Trx homolog, MLL1, deposits H3K4me2 at CpG-dense regions that could serve as PREs. In the absence of MLL1 and H3K4me2, H3K27me3 levels, a mark of Polycomb repressive complex 2 (PRC2), increase at these loci. By inhibiting PRC2-dependent H3K27me3 in the absence of MLL1, we can rescue expression of these loci, demonstrating a functional balance between MLL1 and PRC2 activities at these sites. Thus, our study provides rules for identifying cell-type-specific functional mammalian PREs within the human genome.

Phenylethyl isothiocyanate reverses cisplatin resistance in biliary tract cancer cells via glutathionylation-dependent degradation of Mcl-1.

Biliary tract cancer (BTC) is a highly malignant cancer. BTC exhibits a low response rate to cisplatin (CDDP) treatment, and therefore, an understanding of the mechanism of CDDP resistance is urgently needed. Here, we show that BTC cells develop CDDP resistance due, in part, to upregulation of myeloid cell leukemia 1 (Mcl-1). Phenylethyl isothiocyanate (PEITC), a natural compound found in watercress, could enhance the efficacy of CDDP by degrading Mcl-1. PEITC-CDDP co-treatment also increased the rate of apoptosis of cancer stem-like side population (SP) cells and inhibited xenograft tumor growth without obvious toxic effects. In vitro, PEITC decreased reduced glutathione (GSH), which resulted in decreased GSH/oxidized glutathione (GSSG) ratio and increased glutathionylation of Mcl-1, leading to rapid proteasomal degradation of Mcl-1. Furthermore, we identified Cys16 and Cys286 as Mcl-1 glutathionylation sites, and mutating them resulted in PEITC-mediated degradation resistant Mcl-1 protein. In conclusion, we demonstrate for the first time that CDDP resistance is partially associated with Mcl-1 in BTC cells and we identify a novel mechanism that PEITC can enhance CDDP-induced apoptosis via glutathionylation-dependent degradation of Mcl-1. Hence, our results provide support that dietary intake of watercress may help reverse CDDP resistance in BTC patients.

Enhancer-associated H3K4 monomethylation by Trithorax-related, the Drosophila homolog of mammalian Mll3/Mll4.

Monomethylation of histone H3 on Lys 4 (H3K4me1) and acetylation of histone H3 on Lys 27 (H3K27ac) are histone modifications that are highly enriched over the body of actively transcribed genes and on enhancers. Although in yeast all H3K4 methylation patterns, including H3K4me1, are implemented by Set1/COMPASS (complex of proteins associated with Set1), there are three classes of COMPASS-like complexes in Drosophila that could carry out H3K4me1 on enhancers: dSet1, Trithorax, and Trithorax-related (Trr). Here, we report that Trr, the Drosophila homolog of the mammalian Mll3/4 COMPASS-like complexes, can function as a major H3K4 monomethyltransferase on enhancers in vivo. Loss of Trr results in a global decrease of H3K4me1 and H3K27ac levels in various tissues. Assays with the cut wing margin enhancer implied a functional role for Trr in enhancer-mediated processes. A genome-wide analysis demonstrated that Trr is required to maintain the H3K4me1 and H3K27ac chromatin signature that resembles the histone modification patterns described for enhancers. Furthermore, studies in the mammalian system suggested a role for the Trr homolog Mll3 in similar processes. Since Trr and mammalian Mll3/4 complexes are distinguished by bearing a unique subunit, the H3K27 demethylase UTX, we propose a model in which the H3K4 monomethyltransferases Trr/Mll3/Mll4 and the H3K27 demethylase UTX cooperate to regulate the transition from inactive/poised to active enhancers.

Polycomb repressive complex 2-dependent and -independent functions of Jarid2 in transcriptional regulation in Drosophila.

Jarid2 was recently identified as an important component of the mammalian Polycomb repressive complex 2 (PRC2), where it has a major effect on PRC2 recruitment in mouse embryonic stem cells. Although Jarid2 is conserved in Drosophila, it has not previously been implicated in Polycomb (Pc) regulation. Therefore, we purified Drosophila Jarid2 and its associated proteins and found that Jarid2 associates with all of the known canonical PRC2 components, demonstrating a conserved physical interaction with PRC2 in flies and mammals. Furthermore, in vivo studies with Jarid2 mutants in flies demonstrate that among several histone modifications tested, only methylation of histone 3 at K27 (H3K27), the mark implemented by PRC2, was affected. Genome-wide profiling of Jarid2, Su(z)12 (Suppressor of zeste 12), and H3K27me3 occupancy by chromatin immunoprecipitation with sequencing (ChIP-seq) indicates that Jarid2 and Su(z)12 have very similar distribution patterns on chromatin. However, Jarid2 and Su(z)12 occupancy levels at some genes are significantly different, with Jarid2 being present at relatively low levels at many Pc response elements (PREs) of certain Homeobox (Hox) genes, providing a rationale for why Jarid2 was never identified in Pc screens. Gene expression analyses show that Jarid2 and E(z) (Enhancer of zeste, a canonical PRC2 component) are not only required for transcriptional repression but might also function in active transcription. Identification of Jarid2 as a conserved PRC2 interactor in flies provides an opportunity to begin to probe some of its novel functions in Drosophila development.

The COMPASS family of H3K4 methylases in Drosophila.

Methylation of histone H3 lysine 4 (H3K4) in Saccharomyces cerevisiae is implemented by Set1/COMPASS, which was originally purified based on the similarity of yeast Set1 to human MLL1 and Drosophila melanogaster Trithorax (Trx). While humans have six COMPASS family members, Drosophila possesses a representative of the three subclasses within COMPASS-like complexes: dSet1 (human SET1A/SET1B), Trx (human MLL1/2), and Trr (human MLL3/4). Here, we report the biochemical purification and molecular characterization of the Drosophila COMPASS family. We observed a one-to-one similarity in subunit composition with their mammalian counterparts, with the exception of LPT (lost plant homeodomains [PHDs] of Trr), which copurifies with the Trr complex. LPT is a previously uncharacterized protein that is homologous to the multiple PHD fingers found in the N-terminal regions of mammalian MLL3/4 but not Drosophila Trr, indicating that Trr and LPT constitute a split gene of an MLL3/4 ancestor. Our study demonstrates that all three complexes in Drosophila are H3K4 methyltransferases; however, dSet1/COMPASS is the major monoubiquitination-dependent H3K4 di- and trimethylase in Drosophila. Taken together, this study provides a springboard for the functional dissection of the COMPASS family members and their role in the regulation of histone H3K4 methylation throughout development in Drosophila.

Licensed to elongate: a molecular mechanism for MLL-based leukaemogenesis.

The RNA polymerase II (Pol II) elongation factor (ELL) was the first translocation partner of mixed lineage leukaemia (MLL) for which a biochemical function was determined. It was therefore proposed that the regulation of the elongation stage of transcription could be fundamental to MLL-based leukaemogenesis. Recent studies have identified ELL complexed with several of the translocation partners of MLL in a transcriptional super elongation complex (SEC). These studies provide evidence for the importance of the regulation of Pol II elongation in disease pathogenesis and suggest that MLL chimaeras function by licensing Pol II transcription elongation without the appropriate checkpoints.

Linking H3K79 trimethylation to Wnt signaling through a novel Dot1-containing complex (DotCom).

Epigenetic modifications of chromatin play an important role in the regulation of gene expression. KMT4/Dot1 is a conserved histone methyltransferase capable of methylating chromatin on Lys79 of histone H3 (H3K79). Here we report the identification of a multisubunit Dot1 complex (DotCom), which includes several of the mixed lineage leukemia (MLL) partners in leukemia such as ENL, AF9/MLLT3, AF17/MLLT6, and AF10/MLLT10, as well as the known Wnt pathway modifiers TRRAP, Skp1, and beta-catenin. We demonstrated that the human DotCom is indeed capable of trimethylating H3K79 and, given the association of beta-catenin, Skp1, and TRRAP, we investigated, and found, a role for Dot1 in Wnt/Wingless signaling in an in vivo model system. Knockdown of Dot1 in Drosophila results in decreased expression of a subset of Wingless target genes. Furthermore, the loss of expression for the Drosophila homologs of the Dot1-associated proteins involved in the regulation of H3K79 shows a similar reduction in expression of these Wingless targets. From yeast to human, specific trimethylation of H3K79 by Dot1 requires the monoubiquitination of histone H2B by the Rad6/Bre1 complex. Here, we demonstrate that depletion of Bre1, the E3 ligase required for H2B monoubiquitination, leads specifically to reduced bulk H3K79 trimethylation levels and a reduction in expression of many Wingless targets. Overall, our study describes for the first time the components of DotCom and links the specific regulation of H3K79 trimethylation by Dot1 and its associated factors to the Wnt/Wingless signaling pathway.