Telomere dysfunction causes chromosomal instability which is associated with many cancers and age-related diseases. The non-coding telomeric repeat-containing RNA (TERRA) forms a structural and regulatory component of the telomere that is implicated in telomere maintenance and chromosomal end protection. The basic N-terminal Gly/Arg-rich (GAR) domain of telomeric repeat-binding factor 2 (TRF2) can bind TERRA but the structural basis and significance of this interaction remains poorly understood. Here, we show that TRF2 GAR recognizes G-quadruplex features of TERRA. We show that small molecules that disrupt the TERRA-TRF2 GAR complex, such as N-methyl mesoporphyrin IX (NMM) or genetic deletion of TRF2 GAR domain, result in the loss of TERRA, and the induction of γH2AX-associated telomeric DNA damage associated with decreased telomere length, and increased telomere aberrations, including telomere fragility. Taken together, our data indicates that the G-quadruplex structure of TERRA is an important recognition element for TRF2 GAR domain and this interaction between TRF2 GAR and TERRA is essential to maintain telomere stability.

Objective: This study compared the therapeutic benefits and complication rates of small endoscopic sphincterotomy plus large-balloon dilation (ESLBD) with those of endoscopic sphincterotomy (EST) alone for large bile duct stones. Methods: We compared prospectively ESLBD group (n=63) with conventional EST group (n=69) for the treatment of large bile duct stones (≥15mm). Mechanical lithotripsy was performed when the stone could not be removed using a normal basket. We compared the rates of stone removal, frequency of mechanical lithotripsy use, procedure-related complications, and recurrent stones. Results: A total of 132 patients were reviewed in the study. The mean age of the patients was 67.9 years. The two groups showed significant differences in complete stone removal during the first session (80.9 vs. 60.8%; P = 0.046), the use of mechanical lithotripsy (7.94 vs. 24.6%; P = 0.041), and less duration of admission (P =0.045). After ERCP, there were some instances of oozing in both groups, All patients recovered completely, 14 patients had recurrent common bile duct stones among the follow-up duration. Conclusion: The ESLBD technique seems to be a feasible and safe alternative technique for conventional EST and EBD and has no more Post-ERCP complications.

EBV latent infection is causally linked to diverse cancers and autoimmune disorders. EBNA1 is the viral-encoded DNA binding protein required for episomal maintenance during latent infection and is consistently expressed in all EBV tumors.

Myeloproliferative neoplasms are a group of hematopoietic malignancies that are characterized with the activated JAK2-STAT5 signaling and uncontrolled myeloid cell proliferation. Current first line therapies remain suboptimal with ongoing risks for thrombosis, hemorrhage, impaired quality of life, and risk of transformation to acute leukemia. More recent FDA-approved JAK inhibitors are associated with poor tolerance due to the key roles of JAK2 in normal hematopoiesis. There are unmet medical needs to develop novel targeted therapies to treat the disease. Pleckstrin-2 (Plek2) is a widely expressed PH domain-containing protein that binds to phosphoinositide with unclear functions. We previously showed that Plek2 is overexpressed in JAK2V617F mutation positive myeloproliferative neoplasms (MPNs). We identified that Plek2 is a downstream effector of the JAK2-STAT5 pathway. Furthermore, through a mouse genetic approach, we discovered that knockout of Plek2 significantly ameliorated the MPN phenotypes and reverted lethality and thrombosis in JAK2V617F knock-in mice. These studies demonstrate that Plek2 is critical for the pathogenesis of MPNs with the activated JAK2-STAT5 pathway, and form a strong foundation for the development of Plek2 inhibitors for the treatment of MPNs. Importantly, our published study shows that Plek2 knockout mice do not develop anemia or cytopenia, indicating Plek2's proto-oncogenic function is mainly manifested in the disease background, which makes Plek2 inhibitors less likely to cause severe adverse effects compared to JAK inhibitor ruxolitinib. Based on these studies, we used an in silico approach to screen for putative Plek2 binding small molecules and identified hit compounds that bind to the DEP domain of Plek2. Further medicinal chemistry studies identified lead compound NUP-17d that inhibited proliferation of the hyperproliferative hematopoietic cells with potency comparable to ruxolitinib. In addition, biochemical assays showed that NUP-17d inhibited Akt phosphorylation. Further mechanistic studies revealed that Plek2 promoted Akt-PtdIns(3,4)P2 binding via direct interaction with Akt and enhanced Akt activation; while NUP-17d inhibited this process. In addition to the biochemical assays, we also demonstrated Plek2's function through a mouse genetic approach using a Pten hematopoietic specific knockout mouse model. Knockout of Plek2 significantly reverted the myeloproliferative phenotype in these mice and markedly extended their survival. Therefore, NUP-17d blocks hematopoietic cell proliferation through the disruption of the Plek2 complex and inhibition of the PI3K-Akt pathway. Indeed, treatment of erythropoietin-induced myeloproliferative mouse model and JAK2V617F knock-in model with NUP-17d significantly ameliorated MPN phenotypes including increase in CBC and splenomegaly. These studies establish Plek2 as a oncoprotein mediating JAK2-STAT and PI3K-Akt signaling pathways in myeloproliferative neoplasms. In addition to hematologic malignancies, Plek2 is also found to be highly upregulated with an associated worse prognosis in many solid tumors (data from oncomine, kmplot). Therefore, targeting Plek2 could have a broad impact in cancer therapy, especially in cancers with upregulated JAK2-STAT or PI3K-Akt pathway. Disclosures No relevant conflicts of interest to declare.

Mammalian erythropoiesis is a dynamic process in which erythroid progenitors proliferate and differentiate into mature enucleated red blood cells. In the late stage of terminal erythropoiesis, erythroblasts undergo cell-cycle exit, chromatin condensation, and extrusion of the pycnotic nucleus via an asymmetric cell division. Recent genetic and biochemical studies illustrated that various signaling pathways, including histone deacetylation and other chromatin modifications, are involved in chromatin condensation and enucleation. However, it is unclear the global dynamic changes of the nucleosome and how different histones are regulated during chromatin condensation. We proposed to directly characterize the expression levels and localization of different histones and their variants during erythropoiesis. Using a mouse fetal liver erythroblast in vitro culture system and immunofluorescence analysis, we found an unexpected, gradually enlarged nuclear opening through which most histones, except H2AZ, were released out of the nucleus. The same phenotype was observed in freshly purified fetal liver and bone marrow erythroblasts (Figure 1). These openings lack nuclear lamina, nuclear pore complexes, and nuclear membrane but are distinct from nuclear envelope changes during apoptosis and mitosis. Western blot analysis also demonstrated the nuclear release of a fraction of the major histones, however, many well-known nuclear proteins remained in the nucleus in this process. We also demonstrated that the histone release was cell cycle regulated and independent of nuclear exportin. Using micrococcal nuclease digestion of chromatin followed by next generation sequencing (MNase-seq) technique, we demonstrated that histone release from the nuclear opening is associated with dynamic nucleosomal changes during mouse terminal erythropoiesis. Mechanistically, caspase-3 is involved in the regulation of nuclear openings during erythropoiesis. Inhibition or knockdown of caspase-3 completely blocked nuclear opening formation and histone release, which led to inhibition of chromatin condensation, cell differentiation, and ultimate cell death. In summary, our study revealed a caspase-3 mediated nuclear opening formation with histone release in mouse erythroblasts that is unique in mammalian cells. The dynamic nuclear opening formation is required for fast release of major histones into cytoplasm to facilitate chromatin condensation throughout erythropoiesis. This “prokaryotic phase” of erythroblast is also associated with genome wide nucleosome localization changes that correlate with the size of the nuclear opening and histone release, which may provide clues for the pathogenesis of erythroid related diseases with unknown etiology. Figure 1 Lamin B opening with H2 release in mouse erythropoiesis. (A) E13.5 TER119 negative mouse fetal liver erythroblasts were purified and cultured in vitro in erythropoietin containing medium. Immunofluorescence stains for lamin B, H2A and DNA (DAPI) from erythroblasts cultured on different days were performed. Arrows indicate lamin B openings. Scale bar: 5mm. (B) Same as A except the cells were from fresh total fetal liver cells (left) and bone marrow erythroblasts. Scale bar: 5mm. Figure 1. Lamin B opening with H2 release in mouse erythropoiesis. (A) E13.5 TER119 negative mouse fetal liver erythroblasts were purified and cultured in vitro in erythropoietin containing medium. Immunofluorescence stains for lamin B, H2A and DNA (DAPI) from erythroblasts cultured on different days were performed. Arrows indicate lamin B openings. Scale bar: 5mm. (B) Same as A except the cells were from fresh total fetal liver cells (left) and bone marrow erythroblasts. Scale bar: 5mm. Disclosures No relevant conflicts of interest to declare.