Background Circular RNAs are a class of regulatory RNA transcripts, which are ubiquitously expressed in eukaryotes. In the current study, we evaluate the function of a novel circRNA derived from the β-catenin gene locus, circβ-catenin. Results Circβ-catenin is predominantly localized in the cytoplasm and displays resistance to RNase-R treatment. We find that circβ-catenin is highly expressed in liver cancer tissues when compared to adjacent normal tissues. Silencing of circβ-catenin significantly suppresses malignant phenotypes in vitro and in vivo, and knockdown of this circRNA reduces the protein level of β-catenin without affecting its mRNA level. We show that circβ-catenin affects a wide spectrum of Wnt pathway-related genes, and furthermore, circβ-catenin produces a novel 370-amino acid β-catenin isoform that uses the start codon as the linear β-catenin mRNA transcript and translation is terminated at a new stop codon created by circularization. We find that this novel isoform can stabilize full-length β-catenin by antagonizing GSK3β-induced β-catenin phosphorylation and degradation, leading to activation of the Wnt pathway. Conclusions Our findings illustrate a non-canonical function of circRNA in modulating liver cancer cell growth through the Wnt pathway, which can provide novel mechanistic insights into the underlying mechanisms of hepatocellular carcinoma. Electronic supplementary material The online version of this article (10.1186/s13059-019-1685-4) contains supplementary material, which is available to authorized users.

Previously, we identified a new mammalian sHSP, MKBP, as a myotonic dystrophy protein kinase-binding protein, and suggested its important role in muscle maintenance (Suzuki, A., Sugiyama, Y., Hayashi, Y., Nyu-i, N., Yoshida, M., Nonaka, I., Ishiura, S., Arahata, K., and Ohno, S. (1998) J. Cell Biol. 140, 1113-1124). In this paper, we develop the former work by performing extensive characterization of five of the six sHSPs so far identified, that is, HSP27, ␣B-crystallin, p20, MKBP/ HSPB2, and HSPB3, omitting lens-specific ␣A-crystallin. Tissue distribution analysis revealed that although each sHSP shows differential constitutive expression in restricted tissues, tissues that express all five sHSPs are only muscle-related tissues. Especially, the expressions of HSPB3, identified for the first time as a 17-kDa protein in this paper, and MKBP/HSPB2 are distinctly specific to muscles. Moreover, these sHSPs form an oligomeric complex with an apparent molecular mass of 150 kDa that is completely independent of the oligomers formed by HSP27, ␣B-crystallin, and p20. The expressions of MKBP/HSPB2 and HSPB3 are induced during muscle differentiation under the control of MyoD, suggesting that the sHSP oligomer comprising MKBP/ HSPB2 and HSPB3 represents an additional system closely related to muscle function. The functional divergence among sHSPs in different oligomers is also demonstrated in several ways: 1) an interaction with myotonic dystrophy protein kinase, which has been suggested to be important for the maintenance of myofibril integrity, was observed only for MKBP/HSPB2; 2) a myotube-specific association with actin bundles was observed for HSP27 and ␣B-crystallin, but not for MKBP/ HSPB2; and 3) sHSPs whose mRNAs are induced by heat shock are ␣B-crystallin and HSP27. Taken together, the results suggest that muscle cells develop two kinds of stress response systems composed of diverged sHSP members, and that these systems work independently in muscle maintenance and differentiation.Heat shock and numerous other stress conditions lead to the rapid induction of several genes whose protein products, collectively called heat shock proteins (HSPs), 1 play protective roles in cell survival (1). Considering that muscles are frequently subjected to severe conditions caused by heat, oxidative, and mechanical stresses, especially during exercise (2), these HSPs may be especially important in this particular tissue. In fact, several HSPs, including HSP60, 70, and 90, have been shown to be induced after exhaustive exercise (3). In addition, the inducible isoform of HSP70 has been shown to be constitutively expressed in a certain type of skeletal muscle fiber (4), suggesting that muscle cells are chronically ready to respond to frequent stresses. However, there have been limited numbers of studies that focus on HSPs in muscle cells.HSPs with low molecular masses of 15-30 kDa are called small heat shock proteins (sHSPs); they commonly share a homologous sequence of about 80 amino acids called the "␣-crystallin domain" (5). Among ...

An HDM genome draft produced from genomic, transcriptomic, and proteomic experiments revealed allergen genes and a diverse endosymbiotic microbiome, providing a tool for further identification and characterization of HDM allergens and development of diagnostics and immunotherapeutic vaccines.

An outbreak of severe acute respiratory syndrome (SARS) occurred in China and the first case emerged in mid-November 2002. The aetiological agent of this disease was found to be a previously unknown coronavirus, SARS-associated coronavirus (SARS-CoV). The detailed pathology of SARS-CoV infection and the host response to the viral infection are still not known. The 3a gene encodes a non-structural viral protein, which is predicted to be a transmembrane protein. In this study, it was shown that the 3a protein was expressed in the lungs and intestinal tissues of SARS patients and that the protein localized to the endoplasmic reticulum in 3a-transfected monkey kidney Vero E6 cells. In vitro experiments of chromatin condensation and DNA fragmentation suggested that the 3a protein may trigger apoptosis. These data showed that overexpression of a single SARS-CoV protein can induce apoptosis in vitro.

HBV genotype C can be differentiated into 2 subgroups--namely, genotype Ce and genotype Cs--that have different epidemiological distributions and virological characteristics.