Argonaute proteins are active throughout the lifetime in a variety of organisms and they bind to small RNAs (sRNAs) to regulate gene expression. The Argonaute proteins of vertebrates can be classified into two clades: the Ago clade and the Piwi clade. Both clades have N, L1, L2, PAZ, MID and PIWI domains. The N domain is involved in the loading of sRNAs. L1 and L2 domains facilitate the linking between domains. The PAZ and MID domains exert functions by anchoring sRNAs. The PIWI domain of some Argonaute proteins has RNase H-like structure and exerts the endonuclease function. Ago proteins regulate gene expression at transcriptional and post-transcriptional levels. Piwi proteins mainly exist in the germ cells, silencing transposons in different ways to keep genome integrality and regulating gene expression. In recent years, great progress has been made in Argonaute proteins in terms of the crystal structures, functions, and expression patterns. By reviewing the relevant studies, we elaborate on the structures, sRNA dependence, gene expression regulation, and biological roles of the Ago and Piwi proteins in vertebrates, aiming to clarify the roles of Argonaute proteins in epigenetic regulation and provide a reference for further research and application of these proteins.
Argonaute Proteins/chemistry* ; Animals ; Vertebrates/metabolism* ; Gene Expression Regulation ; RNA, Small Interfering/metabolism* ; Epigenesis, Genetic ; Humans

OBJECTIVETo observe the histological features of tumor-bearing tissues formed by human fibroblasts after reprograming by spermatogonial stem cell self-renewal key regulating gene Piwil2 (Piwil2-iCSC).

METHODSPiwil2-iCSC tumor spheroids-like colonies were selected for tumor formation assay in four nude mice. Pathological features of Piwil2-iCSC tumors were observed by histology. Stem cell markers and common triploblastic markers were detected by reverse transcriptase-polymerase chain reaction (RT-PCR) assay and immunohistochemistry. Germ cell tumor markers were detected by immunohistochemical examination.

RESULTSTwo weeks after inoculation, subcutaneous tumors were formed in all the four nude mice with a tumor formation rate of 100%. In the Piwil2-iCSC tumor tissues, Piwil2-GFP(+) cells showed high-density nuclear expression and were widely observed in DAPI-stained sections. Numerous mitotic figure of the neoplastic cells were seen (>10 cells/field of vision under high magnification) in HE-stained sections. Enlarged abnormal cell nuclei were observed. RT-PCR assay showed that Piwil2-iCSC tumors still expressed Piwil2 and some self-renewal and pluripotent markers of stem cells and some markers of triploblastic differentiation. Immunohistochemical staining showed that the tumors expressed stem cell markers, triploblastic markers and germ cell tumor markers AFP and HCG.

CONCLUSIONSPiwil2-iCSC tumors are probably undifferentiated embryonic small cell carcinoma, most likely to be immature teratoma, mixed with yolk sac tumor and choriocarcinoma components. It can be used as a useful model for the research of origin or genesis mechanism of cancer stem cells and the treatment of relevant tumors.

Adult Stem Cells ; Animals ; Argonaute Proteins ; genetics ; Cellular Reprogramming Techniques ; Choriocarcinoma ; pathology ; Endodermal Sinus Tumor ; pathology ; Fibroblasts ; metabolism ; pathology ; Humans ; Immunohistochemistry ; Mice ; Mice, Nude ; Neoplasms, Germ Cell and Embryonal ; chemistry ; genetics ; pathology ; Neoplastic Stem Cells ; chemistry ; pathology ; Real-Time Polymerase Chain Reaction ; Spheroids, Cellular ; Teratoma ; pathology ; Time Factors

OBJECTIVETo analyze the amino acid sequence composition, secondary structure, the spatial conformation of its domain and other characteristics of Argonaute protein.

METHODSBioinformatics tools and the internet server were used. Firstly, the amino acid sequence composition features of the Argonaute protein were analyzed, and the phylogenetic tree was constructed. Secondly, Argonaute protein's distribution of secondary structure and its physicochemical properties were predicted. Lastly, the protein functional expression form of the domain group was established through the Phyre-based analysis on the spatial conformation of Argonaute protein domains.

RESULTS593 amino acids were encoded by Argonaute protein, the phylogenetic tree was constructed, and Argonaute protein's distribution of secondary structure and its physicochemical properties were obtained through analysis. In addition, the functional expression form which comprised the N-terminal PAZ domain and C-terminal Piwi domain for the Argonaute protein was obtained with Phyre.

CONCLUSIONSThe information relationship between the structure and function of the Argonaute protein can be initially established with bioinformatics tools and the internet server, and this provides the theoretical basis for further clarifying the function of Schistosoma Argonaute protein.

Animals ; Argonaute Proteins ; chemistry ; genetics ; Chemical Phenomena ; Cluster Analysis ; Computational Biology ; methods ; Models, Molecular ; Phylogeny ; Protein Conformation ; Schistosoma ; chemistry ; genetics ; Sequence Homology, Amino Acid