The highly conserved Argonaute protein family members play a central role in the regulation of gene expression networks, orchestrating the establishment and the maintenance of cell identity throughout the entire life cycle, as well as in several human disorders, including cancers. Four functional Argonaute proteins (AGO1-4), with high structure similarity, have been described in humans and mice. Interestingly, only AGO2 is robustly expressed during human and mouse early development, in contrast to the other AGOs. Consequently, AGO2 is indispensable for early development in vivo and in vitro. Here, we review the roles of Argonaute proteins during early development by focusing on the interplay between specific domains of the protein and their function. Moreover, we report recent works highlighting the importance of AGO posttranslational modifications in cancer.

Natural aggregates of a Swiss Braunerde and synthetic soil aggregates produced with several polysaccharides were subjected to various chemical treatments designed to destroy polysaccharides or other soil constituents. The water stability of the aggregates was determined before and after the treatment to evaluate the rǒle of the constituent destroyed. The properties of the agent responsible for the aggregation of soil are discussed. The contrasting behaviour of natural and synthetic aggregates provides evidence against polysaccharides being the agents responsible for the natural aggregation and it appears that more than one agent may be involved in this.

When a very diluted iron(III)chloride solution is slowly alkalified by a weak base, the deprotonation of [Fe(H2O)6]3+ proceeds in a first stage to form mono‐ and dinuclear hydroxoaquo‐complexes. In a second stage 4 dimers condense around a chloride ion to form an eight membered ring, an embryon, which grows fast to very small crystals of the composition Fe4O3(OH)5Cl and the structure of the β‐FeOOH. These crystalline micells remain colloidally dissolved. If the pH is raised above approximately 3.4 the Cl−‐ are exchanged against OH−‐ions and flocculation occurs. This shows that Pauli, assuming the micells of such sols to be polynuclear complex ions, is basically correct, and it follows that micells can also be micro‐crystals. When an iron(III)chloride solution is neutralized fast with a strong base, an ‘amorphous’ precipitation is obtained which gives with MoKα‐X‐rays only two broad reflections, showing that the iron oxide hydroxide octahedra are condensed in a highly disordered way. The coherently scattering areas of this precipitate are probably tetramers. Small amounts of primarily formed amorphous iron(III)hydroxide are transformed into β‐FeOOH.

Argonaute proteins (AGOs), which play an essential role in cytosolic post-transcriptional gene silencing, have been also reported to function in nuclear processes like transcriptional activation or repression, alternative splicing and, chromatin organization. As most of these studies have been conducted in human cancer cell lines, the relevance of AGOs nuclear functions in the context of mouse early embryonic development remains uninvestigated. Here, we examined a possible role of the AGO1 protein on the distribution of constitutive heterochromatin in mouse embryonic stem cells (mESCs). We observed a specific redistribution of the repressive histone mark H3K9me3 and the heterochromatin protein HP1α, away from pericentromeric regions upon Ago1 depletion. Furthermore, we demonstrated that major satellite transcripts are strongly up-regulated in Ago1_KO mESCs and that their levels are partially restored upon AGO1 rescue. We also observed a similar redistribution of H3K9me3 and HP1α in Drosha_KO mESCs, suggesting a role for microRNAs (miRNAs) in the regulation of heterochromatin distribution in mESCs. Finally, we showed that specific miRNAs with complementarity to major satellites can partially regulate the expression of these transcripts.