Distinct epigenetic landscapes underlie the pathobiology of pancreatic cancer subtypes.

Recent studies have offered ample insight into genome-wide expression patterns to define pancreatic ductal adenocarcinoma (PDAC) subtypes, although there remains a lack of knowledge regarding the underlying epigenomics of PDAC. Here we perform multi-parametric integrative analyses of chromatin immunoprecipitation-sequencing (ChIP-seq) on multiple histone modifications, RNA-sequencing (RNA-seq), and DNA methylation to define epigenomic landscapes for PDAC subtypes, which can predict their relative aggressiveness and survival. Moreover, we describe the state of promoters, enhancers, super-enhancers, euchromatic, and heterochromatic regions for each subtype. Further analyses indicate that the distinct epigenomic landscapes are regulated by different membrane-to-nucleus pathways. Inactivation of a basal-specific super-enhancer associated pathway reveals the existence of plasticity between subtypes. Thus, our study provides new insight into the epigenetic landscapes associated with the heterogeneity of PDAC, thereby increasing our mechanistic understanding of this disease, as well as offering potential new markers and therapeutic targets.

Postnatal Ontogenesis of the Islet Circadian Clock Plays a Contributory Role in ß-Cell Maturation Process.

Development of cell replacement therapies in diabetes requires understanding of the molecular underpinnings of ß-cell maturation. The circadian clock regulates diverse cellular functions important for regulation of ß-cell function and turnover. However, postnatal ontogenesis of the islet circadian clock and its potential role in ß-cell maturation remain unknown. To address this, we studied wild-type Sprague-Dawley as well as Period1 luciferase transgenic (Per1:LUC) rats to determine circadian clock function, clock protein expression, and diurnal insulin secretion during islet development and maturation process. We additionally studied ß-cell-specific Bmal1-deficient mice to elucidate a potential role of this key circadian transcription factor in ß-cell functional and transcriptional maturation. We report that emergence of the islet circadian clock 1) occurs during the early postnatal period, 2) depends on the establishment of global behavioral circadian rhythms, and 3) leads to the induction of diurnal insulin secretion and gene expression. Islet cell maturation was also characterized by induction in the expression of circadian transcription factor BMAL1, deletion of which altered postnatal development of glucose-stimulated insulin secretion and the associated transcriptional network. Postnatal development of the islet circadian clock contributes to early-life ß-cell maturation and should be considered for optimal design of future ß-cell replacement strategies in diabetes.

CARM1-expressing ovarian cancer depends on the histone methyltransferase EZH2 activity.

CARM1 is an arginine methyltransferase that asymmetrically dimethylates protein substrates on arginine residues. CARM1 is often overexpressed in human cancers. However, clinically applicable cancer therapeutic strategies based on CARM1 expression remain to be explored. Here, we report that EZH2 inhibition is effective in CARM1-expressing epithelial ovarian cancer. Inhibition of EZH2 activity using a clinically applicable small molecule inhibitor significantly suppresses the growth of CARM1-expressing, but not CARM1-deficient, ovarian tumors in two xenograft models and improves the survival of mice bearing CARM1-expressing ovarian tumors. The observed selectivity correlates with reactivation of EZH2 target tumor suppressor genes in a CARM1-dependent manner. Mechanistically, CARM1 promotes EZH2-mediated silencing of EZH2/BAF155 target tumor suppressor genes by methylating BAF155, which leads to the displacement of BAF155 by EZH2. Together, these results indicate that pharmacological inhibition of EZH2 represents a novel therapeutic strategy for CARM1-expressing cancers.

Structure based energy calculation to determine the regulation of G protein signalling by RGS and RGS-G protein interaction specificity.

The RGS proteins act as GTPase activating proteins and therefore regulate the lifespan of the active G alpha-GTP by accelerating the GTP hydrolysis. Modulatory residues in the RGS protein are present at the periphery of the RGS domain-G protein interface which is essential to fine-tune the G protein recognition and interaction. The docking energies of the mutant complex and the native complex were compared to see the effects of the mutations in the Modulatory regions. Mutations of Modulatory residues in high-activity RGS proteins lead to loss of function, whereas multiple mutations in the low-activity RGS proteins in critical Modulatory positions lead to complete gain of function. In the RGS proteins the Significant and Conserved core residues with peripheral Modulatory residues selectively optimize G protein recognition and inactivation. The flexibility of the structures of the mutant complexes were seen to be higher and the accessible surface area for the complexes increased after the mutations in the Modulatory residues. Through this approach we analyzed the interaction specificity among the RGS and the G alpha protein, the approach can also be applied to other protein families to find the residues which along with the core binding domain, fine tune the protein recognition and are crucial in the loss or gain of function.