All information updated in 2020

Guest Speaker – Julien Bethuné

On Thursday, 30.01.2020, 5.15 pm


Julien Bethuné (Heidelberg University Biochemistry Center), will give an SFB 902 lecture:

„Analysis of context-dependent protein complexes with next-generation
proximity proteomics assays“

Venue: TU Darmstadt, Campus Botanischer Garten, lecture hall: B101/52

Guests are welcome!
Since its initial description in 2012, the proximity-dependent biotinylation technique BioID has
established itself as a reliable alternative to the classical Affinity Purification-MS approach for the
identification of protein-protein interactions. Recently we engineering split-BioID, a proteinfragments
complementation assay that greatly enhances the resolution of BioID by allowing the
analysis of context-dependent protein complexes. Applied to the miRNA silencing pathway, split-
BioID let us identify the 4EHP-binding protein GIGYF2 as a novel miRISC-associated factor. The 4EHPGIGYF2
dimer has been proposed to be recruited by RNA-binding proteins to stimulate the
repression of translation of their associated transcripts. In line with this model we found that the
miRISC component TNRC6 directly binds to GIGYF2 which in turns promotes miRNA-mediated
translation repression. More recently we uncovered an additional mechanism of GIGYF2-mediated
repression that is independent of 4EHP but rather relies on the CCR4-NOT deadenylation complex.
This suggests that GIGYF2 is part of two distinct functional units that exert distinct modes of
repression on their associated target mRNAs. To define the composition of these context-dependent
GIGYF2 complexes, we have developed more versatile proximity labeling assays that rely on a smaller
labeling enzyme with improved labeling kinetics and that can be used in a split assay format.

Guest Speaker – Neva Caliskan

On Tuesday, 28.01.2020, 5.15 pm


Neva Caliskan (Helmholtz-Institut für RNA-basierte Infektionsforschung, Würzburg), will give an SFB 902 lecture:

„Single-Molecule and Ensemble Analysis of Protein-mediated Frameshifting“.

Venue: Campus Riedberg, lecture hall: N260/3.13

Guests are welcome!
Three bases encoding for an amino acid seem to represent the universal feature of the genetic code, yet ribosomes have evolved to read the code in different ways by altering the triplet periodicity of the reading frame. This phenomenon is called programmed ribosome frameshifting (PRF). PRF requires specific cis-acting elements – a slippery site followed by a stable RNA structure. PRF efficiency is also affected by trans-acting factors, including proteins, miRNAs and metabolites. While the general mechanisms of PRF and the involvement of cis-acting elements in this process are well understood, the regulation of these events is still vastly understudied. Additionally, the interactions of these factors with the RNA and the translation machinery have not yet been completely understood. Recent advances in single-molecule techniques allow to study these events at the molecular level and thus unveil hitherto unrecognised details. In this study, we chose the encephalomyocarditis virus (EMCV) 2A protein as a model to study PRF regulation. The expression of this protein is essential for frameshifting on the EMCV mRNA, and inhibition of PRF leads to severely reduced virulence. We investigated the interplay of the 2A protein with its frameshifting-RNA target. To do so, we combined single-molecule techniques, such as optical tweezers and confocal microscopy, together with HPLC-MS and microscale thermophoresis (MST). We anticipate these assays to be a starting point in analysing the translational kinetics of frameshifting and its interplay by RNA binding factors. Furthermore, recent examples of identification of such factors indicate that they play a major role in PRF regulation and understanding their mode of action will certainly uncover new fundamental principles of RNA-based gene regulation.