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Pediatric neuroblastomas (NBs) are heterogeneous, aggressive, therapy-resistant embryonal tumors that originate from cells of neural crest origin committed to the sympathoadrenal progenitor cell lineage. Stress- and drug-resistance mechanisms drive post-therapeutic relapse and metastatic progression, the characterization and inhibition of which are major goals in improving therapeutic responses. Stress- and drug-resistance mechanisms in NBs include alternative TrkAIII splicing of the neurotrophin receptor tropomyosin-related kinase A (NTRK1/TrkA), which correlates with post-therapeutic relapse and advanced-stage metastatic disease. The TrkAIII receptor variant exerts oncogenic activity in NB models by mechanisms that include stress-induced mitochondrial importation and activation. In this study, we characterize novel targetable and non-targetable participants in this pro-survival mechanism in TrkAIII-expressing SH-SY5Y NB cells, using dithiothreitol (DTT) as an activator and a variety of inhibitors by regular and immunoprecipitation Western blotting of purified mitochondria and IncuCyte cytotoxicity assays. We report that stress-induced TrkAIII misfolding initiates this mechanism, resulting in Grp78, Ca2+-calmodulin, adenosine ribosylating factor (Arf) and Hsp90-regulated mitochondrial importation. TrkAIII imported into inner mitochondrial membranes is cleaved by Omi/high temperature requirement protein A2 (HtrA2) then activated by a mechanism dependent upon calmodulin kinase II (CaMKII), alpha serine/threonine kinase (Akt), mitochondrial Ca2+ uniporter and reactive oxygen species (ROS), involving inhibitory mitochondrial protein tyrosine phosphatase (PTPase) oxidation, resulting in phosphoinositide 3 kinase (PI3K) activation of mitochondrial Akt, which enhances stress resistance. This novel pro-survival function for misfolded TrkAIII mitigates the cytotoxicity of mitochondrial Ca2+ homeostasis disrupted during integrated stress responses, and is prevented by clinically approved Trk and Akt inhibitors and also by inhibitors of 78kDa glucose regulated protein (Grp78), heat shock protein 90 (Hsp90), Ca2+-calmodulin and PI3K. This identifies Grp78, Ca2+-calmodulin, Hsp90, PI3K and Akt as novel targetable participants in this mechanism, in addition to TrkAIII, the inhibition of which has the potential to enhance the stress-induced elimination of TrkAIII-expressing NB cells, with the potential to improve therapeutic outcomes in NBs that exhibit TrkAIII expression and activation. [ABSTRACT FROM AUTHOR]

The mechanism of skeletal myoblast fusion is not well understood. We show that endogenous nitric oxide (NO) generation is required for myoblast fusion both in embryonic myoblasts and in satellite cells. The effect of NO is concentration and time dependent, being evident only at the onset of differentiation, and direct on the fusion process itself. The action of NO is mediated through a tightly regulated activation of guanylate cyclase and generation of cyclic guanosine monophosphate (cGMP), so much so that deregulation of cGMP signaling leads to a fusion-induced hypertrophy of satellite-derived myotubes and embryonic muscles, and to the acquisition of fusion competence by myogenic precursors in the presomitic mesoderm. NO and cGMP induce expression of follistatin, and this secreted protein mediates their action in myogenesis. These results establish a hitherto unappreciated role of NO and cGMP in regulating myoblast fusion and elucidate their mechanism of action, providing a direct link with follistatin, which is a key player in myogenesis.

Ezh2 expression was developmentally regulated in the myotome compartment of mouse somites and its down-regulation coincided with activation of muscle gene expression and differentiation of satellite-cell-derived myoblasts. Both Ezh2 and YY1 were detected, with the deacetylase HDAC1 at genomic regions of silent muscle-specific genes.

Analyzes Che-1 expression in multiple matched tumor/normal clinical samples from the colon. Down-regulation and overexpression of Che-1 in several human cancers, including in colon carcinomas; Results showing that Che-1 down-regulation is involved in colon carcinoma proliferation and supporting Che-1 as a general GDAC1 competitor.

Summary: Che-1 is a RNA polymerase II-binding protein involved in the transcription of E2F target genes and induction of cell proliferation. Here we show that Che-1 contributes to DNA damage response and that its depletion sensitizes cells to anticancer agents. The checkpoint kinases ATM/ATR and Chk2 interact with Che-1 and promote its phosphorylation and accumulation in response to DNA damage. These Che-1 modifications induce a specific recruitment of Che-1 on the TP53 and p21 promoters. Interestingly, it has a profound effect on the basal expression of p53, which is preserved following DNA damage. Notably, Che-1 contributes to the maintenance of the G2/M checkpoint induced by DNA damage. These findings identify a mechanism by which checkpoint kinases regulate responses to DNA damage. [Copyright &y& Elsevier]

miR-122 is the most abundant microRNA (miRNA) in the liver; it regulates several genes mainly involved in cell metabolism and inflammation. Host factors, diet, metabolic disorders and viral infection promote the development of liver diseases, including hepatocellular carcinoma (HCC). The downregulation of miR-122 in tissue is a common feature of the progression of liver injury. In addition, the release of miR-122 in the bloodstream seems to be very promising for the early diagnosis of both viral and non-viral liver disease. Although controversial data are available on the role of circulating miR-122 as a single biomarker, high diagnostic accuracy has been observed using miR-122 in combination with other circulating miRNAs and/or proteins. This review is focused on comprehensively summarizing the most recent literature on the potential role of circulating miR-122, and related molecules, as biomarker(s) of metabolic liver diseases, hepatitis and HCC.

RNA polymerase II core subunit 3 (RPB3) is an a-like core subunit of RNA polymerase II (pol II). It is selectively down-regulated upon treatment with doxorubicin (dox). Due to the failure of skeletal muscle cells to differentiate when exposed to dox, we hypothesized that RPB3 is involved in muscle differentiation. To this end, we have isolated human muscle RPB3-interacting proteins by using yeast two-hybrid screening. It is of interest that an interaction between RPB3 and the myogenic transcription factor myogenin was identified. This interaction involves a specific region of RPB3 protein that is not homologous to the prokaryotic a subunit. Although RPB3 contacts the basic helix-loop-helix (HLH) region of myogenin, it does not bind other HLH myogenic factors such as MyoD, Myf5, and MRF4. Coimmunoprecipitation experiments indicate that myogenin contacts the pol II complex and that the RPB3 subunit is responsible for this interaction. We show that RPB3 expression is regulated during muscle differentiation. Exogenous expression of RPB3 slightly promotes myogenin transactivation activity and muscle differentiation, whereas the region of RPB3 that contacts myogenin, when used as a dominant negative molecule (Sud), counteracts these effects. These results indicate for the first time that the RPB3 pol II subunit is involved in the regulation of tissue-specific transcription.