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Double-stranded DNAs are usually present in the form of linear B-form double-helix with the base pairs of adenine (A) and thymine (T) or cytosine (C) and guanine (G), but G-rich DNA can form four-stranded G-quadruplex (G4) structures, which plays important roles in transcription, replication, translation and protection of telomeres. In this study, a RNA recognition motif (RRM)-containing protein, BmLARK, was identified and demonstrated to bind G4 structures in the promoters of a transcription factor BmPOUM2 and other three unidentified genes of Bombyx mori , as well as three well-defined G4 structures in the human genes. Homologous LARKs from Bombyx mori, Drosophila melanogaster, Mus musculus and Homo sapiens bound G4 structures in BmPOUM2 and other genes in B. mori and H. sapiens . Upon binding, LARK facilitated the formation and stability of the G4 structure, enhancing the transcription of target genes. The G4 structure was visualized in vivo in cells and testis from invertebrate B. mori and vertebrate Chinese hamster ovary (CHO) cells. The results of this study strongly suggest that LARK is a novel and conserved G4-binding protein and that the G4 structure may have developed into an elaborate epigenetic mechanism of gene transcription regulation during evolution.

Background/Aims: Thyroid cancer is one of the most prevalent endocrine tumors. The present study examined the effects of lncRNA HOXA cluster antisense RNA2 (HOXA-AS2) on the progression of papillary thyroid cancer (PTC), and explored the underlying molecular mechanisms. Methods: Quantitative real-time PCR was used to detect HOXA-AS2, miR-520c-3p and S100 calcium-binding protein A4 (S100A4) expression. Furthermore, the effects of HOXA-AS2 silencing and overexpression on cell proliferation, migration, and invasion were assessed in PTC in vitro by CCK8 and transwell assay. Furthermore, bioinformatics online programs predicted and luciferase reporter assay were used to validate the association of HOXA-AS2 and miR-520c-3p in PTC. Results: We observed that HOXA-AS2 was up-regulated in PTC tissues. In vitro experiments revealed that HOXA-AS2 knockdown significantly inhibited cell growth in PTC in vitro and in vivo. Further functional assays indicated that HOXA-AS2 significantly promoted PTC cell migration and invasion by promoting EMT. Bioinformatics online programs predicted that HOXA-AS2 sponge miR-520c-3p at 3’-UTR with complementary binding sites, which was validated using luciferase reporter assay. HOXA-AS2 could negatively regulate the expression of miR-520c-3p in PTC cells. MiR-520c-3p was down-regulated in PTC tissues, and S100A4 was predicted as a downstream target of miR-520c-3p, which was confirmed by luciferase reporter assay. Conclusion: In summary, our results suggested that the HOXA-AS2/miR-520c-3p/S100A4 axis may play an important role in the regulation of PTC progression, which provides us with new insights into understanding the PTC.

ZNF703, a member of the NET/Nlz family of zinc finger transcription factors, contributes to aspects of developmental growth and patterning across evolutionarily diverse species. ZNF703 has been identified as a novel oncogene in human breast cancer. In the present study, we investigated the expression of ZNF703 in gastric carcinoma and attempted to determine, using cell line models, its biological actions. Using immunohistochemistry, we analyzed the ZNF703 protein expression in 120 clinicopathologically characterized gastric cancer cases. Using RNA interference, we investigated the effects of ZNF703 depletion on tumor proliferation and metastasis in vitro. We found that ZNF703 was overexpressed in invasive gastric carcinoma tissues, and its expression levels were closely correlated with the depth of invasion, node metastasis and venous invasion. RNA interference-mediated silencing of the ZNF703 gene in SGC7901 cells inhibited cell proliferation and migration significantly. The results showed that ZNF703 acts as a gastric cancer oncogene and should be considered a therapeutic target for metastatic gastric cancer.