Endogenous retroviruses (ERVs) contribute to ∼10 percent of the mouse genome. They are often silenced in differentiated somatic cells but differentially expressed at various embryonic developmental stages. A minority of mouse embryonic stem cells (ESCs), like 2-cell cleavage embryos, highly express ERV MERVL. However, the role of ERVs and mechanism of their activation in these cells are still poorly understood. In this study, we investigated the regulation and function of the stage-specific expressed ERVs, with a particular focus on the totipotency marker MT2/MERVL. We show that the transcription factor Zscan4c functions as an activator of MT2/MERVL and 2-cell/4-cell embryo genes. Zinc finger domains of Zscan4c play an important role in this process. In addition, Zscan4c interacts with MT2 and regulates MT2-nearby 2-cell/4-cell genes through promoting enhancer activity of MT2. Furthermore, MT2 activation is accompanied by enhanced H3K4me1, H3K27ac, and H3K14ac deposition on MT2. Zscan4c also interacts with GBAF chromatin remodelling complex through SCAN domain to further activate MT2 enhancer activity. Taken together, we delineate a previously unrecognized regulatory axis that Zscan4c interacts with and activates MT2/MERVL loci and their nearby genes through epigenetic regulation.

The application of fluorescent graphitic carbon nitride (g-C 3 N 4 ) nanomaterials was limited by short photoluminescence (PL) wavelength. It is great desirable to develop g-C 3 N 4 nanomaterials with long PL wavelength and high quantum yield to expand their application. Herein phenyl-modified and sulfur doped g-C 3 N 4 (PhCNS) powders with tunable PL peak from 520 to 630 nm were prepared by copolymerization of 2,4diamino-6-phenyl-1,3,5-triazine and trithiocyanuric acid. The copolymerization process of PhCNS powders was proposed after chemical structure characterization and PL mechanism of PhCNS powders were investigated by transient fluorescence. In virtue of tunable PL color, broad PL peak, and high quantum yield, PhCNS powders were utilized to fabricate green, yellow, and white light-emitting diodes with high color quality and PhCNS nanosheets were applied for multicolor bioimaging. This work provides a pathway for exploring g-C 3 N 4 nanomaterials with long PL wavelength and facilitates their application in biocompatible optoelectronic devices, fluorescent bioimaging.

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These data suggest that KISS1 is down-regulated in cancer tissues via promoter hypermethylation and therefore may represent a candidate target for treating metastatic CRC.