Coding and non-coding RNAs are regulated at numerous levels. For example, microRNA (miRNA) expression can be influenced at various steps of biosynthesis. Furthermore, it has been reported that direct RNA methylation events can also affect gene expression in many different organisms and systems. The aim of this project is to identify and characterize factors that affect the maturation of miRNAs. We will employ biochemical pull down assays to isolate specific binding partners of different miRNA species. We will analyze the physiological role of these factors using molecular or cell biological approaches. Molecular details of pre-miRNA-protein interactions will be investigated by x-ray crystallography. In addition, we will decipher the role of the m6A methylation pathway on the regulation of coding and non-coding RNAs. Writers, readers and erasers of this modification have been identified. However, not much is known about the composition of specific protein complexes as well as the atomic structure of these factors. Thus, we will functionally and structurally characterize known and putative novel factors of the m6A methylation pathway in human cells. Furthermore, using our biochemical pull down approach employed for the identification of pre-miRNA processing factors, we will identify reader proteins of several types of RNA modification that have not been investigated so far. The proposed project will elucidate the regulation of gene expression by small RNAs or direct RNA methylation and will add so far unknown components to these important regulatory pathways.
The direct catalytic functionalization of C-H bonds, an ubiquitous motif in organic molecules, represents a paradigm shift in the standard logic of organic synthesis. One of the major challenges to render this approach synthetically useful is to control the site-selectivity because most organic molecules exhibit several similar aliphatic C-H bonds. The functionalization of aliphatic C-H bond mediated by photoredox catalysis is a highly active field of research. To date, state-of-the-art site-selective methods in this field rely on substrate control which are inherently restricted to the functionalization of a single C-H bond within the substrate backbone. The innovative aspect of this research program is to target catalyst control to allow the site-selective functionalization of several different C-H bonds of a single substrate. Through this approach, we wish to go beyond the challenging problem of site-selectivity to enable site-divergent functionalizations. Such a breakthrough would provide a new tool for a flexible and streamlined access to molecular complexity from chemical feedstocks. To achieve our objectives, we plan to develop novel bifunctional catalysts incorporating one moiety able to engage into dynamic non-covalent interactions with the substrate and another functional group able to perform Hydrogen Atom Transfer (HAT) processes. These two functional groups are connected by an inert spacer which will position the HAT unit in proximity to a particular C-H bond of the substrate, thus controlling site-selectivity for the C-H activation event. By varying the nature of the spacer, we expect to selectively functionalize several different positions of linear alkyl chains possessing almost undistinguishable methylene C-H bonds. Overall, BICACH aims at using simple bifunctional organocatalysts and light energy to trigger highly challenging C-H functionalization processes. In addition, it offers a unique training to the ER with broad future research perspectives.