לוח שנה משולב

RNA interference (RNAi), a gene-silencing pathway triggered by double-stranded RNA (dsRNA), is conserved in diverse eukaryotic species but has been lost in the model budding yeast, Saccharomyces cerevisiae.  We have shown that RNAi is present in other budding-yeast species, including Saccharomyces castellii, Klyuveromyces polysporus and Candida albicans.  To generate small interfering RNAs (siRNAs) these species use non-canonical Dicer proteins that probably emerged from a duplication event of another ribonuclease III enzyme in the budding-yeast lineage. The siRNAs in all three budding-yeast species mostly correspond to transposons and Y´ subtelomeric repeats indicating a role of RNAi in the regulation of such elements.  Reconstituting RNAi in S. cerevisiae by adding pathway components of S. castellii only subtly impacts cellular phenotype but destabilizes a cytoplasmically-inherited dsRNA virus known as Killer virus.  Cells that have lost the Killer virus are at a competitive disadvantage when exposed to the toxin secreted by cells that maintain Killer.  The incompatibility between RNAi and Killer viruses extends to other species; in that RNAi is absent in all fungal species known to possess dsRNA Killer viruses, whereas Killer is absent in closely related species that have retained RNAi.  Thus, the advantage imparted by acquiring and retaining killer viruses explains the persistence of RNAi-deficient species during fungal evolution.

Abstract: In the last years we have explored the formation of vesicles of amphiphilic cyclodextrins and the molecular recognition of guest molecules at the surface of such host vesicles. On the one hand, the molecular recognition and interaction of bilayer vesicles is a versatile model system for the recognition, adhesion and fusion of biological cell membranes. On the other hand, the recognition-induced interaction of vesicles bridges the gap between colloid chemistry and supramolecular chemistry and gives rise to adaptive soft materials.
In this lecture we will highlight our recent work on stimulus responsive adhesion of vesicles. We will show that photosensitive supramolecular linkers can give rise to light-responsive adhesion of vesicles as well as the light-induced capture and release of DNA in a supramolecular lipoplex. Furthermore, we will show that metal-binding supramolecular linkers can result in metal-ion responsive adhesion of vesicles. These dynamic supramolecular systems demonstrate that highly specific molecular recognition can guide the formation of adaptive soft materials.