After a retrovirus particle is released from the cell, the dimeric genomic RNA undergoes a change in conformation. We have previously proposed that this change, termed maturation of the dimer, is due to the action of nucleocapsid (NC) protein on the RNA within the virus particle. We now report that treatment of a 345-base synthetic fragment of Harvey sarcoma virus RNA with recombinant or synthetic HIV-1 NC protein converts a less stable form of dimeric RNA to a more stable form. This phenomenon thus appears to reproduce the maturation of dimeric retroviral RNA in a completely defined system in vitro, To our knowledge, maturation of dimeric RNA within a retrovirus particle is the first example of action of an "RNA chaperone" protein in vivo. Studies with mutant NC proteins suggest that the activity depends upon basic amino acid residues flanking the Nterminal zinc finger and upon residues within the N-terminal finger, including an aromatic amino acid, but do not require the zinc finger structures themselves.After a retrovirus particle is released from the cell, the dimeric genomic RNA within the particle undergoes a change in conformation (1-3). This change, which renders the dimer more thermostable, has been referred to as "maturation" of the dimer; maturation requires the activity of the viral protease (PR) (2, 3).The requirement for PR activity suggested that RNA maturation results from interaction of one or more of the Gag proteins with the RNA after PR-mediated cleavage releases these proteins from the Gag polyprotein precursor. We have specifically suggested (2) that one of these cleavage products, the viral nucleocapsid (NC) protein, is responsible for maturation of the RNA, because (i) NC is known to be associated with the RNA in the nucleoprotein core of the mature particle (4-6), and (ii) NC is known to facilitate the formation of the optimal, most thermodynamically stable structures in nucleic acids (7,8).The nature of the difference between the immature and mature dimeric forms of viral RNA is not known; indeed, the structure of the dimeric RNA in retrovirus particles is very poorly understood. The two monomers are believed to be joined near their 5' ends (9). One important step in the analysis of these structures was the finding that relatively short RNA transcripts containing sequences from near the 5' end of retroviral genomes can dimerize spontaneously in vitro under conditions of high ionic strength (4, 5, 10).In the course of experiments designed to identify sequences from the Harvey sarcoma virus (HaSV) genome capable of dimerization in vitro, we noted (11) that a 345-base transcript could give rise to two distinct dimeric forms differing in thermostability: dimerization at 37°C produces a population of dimeric molecules of which some can be dissociated into monomers at temperatures near 45°C, whereas dimerization at 55°C produces dimers that are all stable to temperatures of 55°C or higher.We now report that incubation of the HaSV dimers formed at 37°C with recombinant or synthetic HIV...

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Background: Hypoxia is a key feature of breast cancer, which affects cancer development, metastasis and metabolism. Previous studies suggested that circular RNAs (circRNAs) could participate in cancer progression and hypoxia regulation. This study aimed to investigate the role of circRNA differentially expressed in normal cells and neoplasia domain containing 4C (circDENND4C) in breast cancer progression under hypoxia. Methods: Forty-three patients with breast cancer were involved in this study. Breast cancer cell lines MDA-MB-453 and SK-BR-3 were cultured under hypoxia (1% O 2) for experiments in vitro. The expression levels of circDENND4C, microRNA-200b (miR-200b) and miR-200c were measured by quantitative real-time polymerase chain reaction. Glycolysis was investigated by glucose consumption, lactate production and hexokinase II (HK2) protein level. Migration and invasion were evaluated via trans-well assay and protein levels of matrix metallopeptidase 9 (MMP9) and MMP2. The interaction between circDENND4C and miR-200b or miR-200c was explored by bioinformatics analysis, luciferase assay and RNA immunoprecipitation. Murine xenograft model was established to investigate the anti-cancer role of circDENND4C in vivo. Results: circDENND4C highly expressed in breast cancer was up-regulated in response to hypoxia. Knockdown of circDENND4C decreased glycolysis, migration and invasion in breast cancer cells under hypoxia. circDENND4C was validated as a sponge of miR-200b and miR-200c. Deficiency of miR-200b or miR-200c reversed the suppressive effect of circDENND4C knockdown on breast cancer progression. Moreover, silence of circDENND4C reduced xenograft tumor growth by increasing miR-200b and miR-200c. Conclusion: circDENND4C silence suppresses glycolysis, migration and invasion in breast cancer cells under hypoxia by increasing miR-200b and miR-200c.

Panobinostat (LBH589) is a highly potent deacetylase inhibitor that has demonstrated clinical efficacy in patients with advanced cutaneous T-cell lymphoma (CTCL). To gain a better understanding of the compound activity in this tumor type, we investigated the cellular and molecular effects of panobinostat using both in vitro and in vivo models of CTCL. All 4 tested CTCL cell lines exhibited very high sensitivity to panobinostat-induced growth inhibition. However, only 2 of 4 lines exhibited significant response to the cytotoxic activity of panobinostat. In a CTCL xenograft mouse tumor model, panobinostat treatment resulted in complete tumor regression. The difference in cell sensitivity to panobinostat-induced death enabled us to further investigate potential mechanisms responsible for tumor sensitivity or resistance. In CTCL cell lines that were insensitive to panobinostat-induced apoptosis, constitutively activated NF-jB and high levels of Bcl-2 were observed. Inhibition of Bcl-2 sensitized cells to the cytotoxic activity of panobinostat. Conversely, knockdown of Bax diminished the CTCL cell sensitivity. Interestingly, panobinostat could induce cytotoxicity in vorinostat-resistant CTCL cells by downregulating phosphorylated STAT3 and STAT5 proteins. These studies suggest distinct mechanisms responsible for resistance to different deacetylase inhibitors. We show that the intrinsic apoptotic signaling plays an essential role in mediating panobinostat anticancer activity. Moreover, cancer cell sensitivity to panobinostat treatment may be further improved by combination with inhibition of anti-apoptotic factors. These data provide preclinical support that panobinostat, as a single agent or in combination with other anticancer agents, is a promising therapy for CTCL.Cutaneous T-cell lymphomas (CTCLs) are lymphoproliferative disorders characterized by clonal expansion and localization of neoplastic T lymphocytes to the skin, resulting in immune dysregulation and tumor growth. 1 The most common form of CTCL is mycosis fungoides (MF), which is typically indolent but may evolve into the leukemic variant, Sézary syndrome (SS) or large-cell lymphoma. Traditionally, a number of skin-directed and systemic therapies are applied to control CTCL progression. Patients with progressed or refractory CTCL generally have a poor prognosis. Subsequent relapses are common in treated MF patients, and few available treatments have impacted overall survival (OS) for CTCL patients, resulting in a serious unmet therapeutic need.Distinct subtypes of CTCL are currently delineated on the basis of clinical or morphological features, and neither underlying pathogenesis of cutaneous lymphomas nor the distinguishing molecular abnormalities have been identified. However, CTCL cells have been shown to have deregulation of apoptotic responses. 2,3 Thus, treatments that can overcome CTCL resistance to apoptosis may provide new therapeutic strategies. To this effect, several novel targeted agents have emerged, which show promise in treating CTCL.Deace...

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