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Jirka Peschek 
RNA Processing and Repair

Groupleader: Jirka Peschek

The cellular pool of ribonucleic acids (RNAs) is immensely diverse and complex. During their biosynthesis, RNA molecules undergo a vast number of co- and posttranscriptional processing and modification steps, which require dedicated enzyme machinery.
tRNA Splicing
One unique example of RNA processing is non-conventional splicing of RNAs, which is an essential step during transfer RNA (tRNA) maturation. tRNAs are transcribed as precursor transcripts (pre-tRNA) and are subjected to multiple posttranscriptional processing events before they can fulfil their function. Intron-containing pre-tRNAs undergo non-conventional splicing—a cytosolic, enzyme-catalysed processing reaction. The splicing of pre-tRNAs occurs in two steps: The intron is first excised by a splicing endonuclease and the resulting tRNA exon halves are ligated by tRNA ligase to form a fully matured functional tRNA. Because eukaryotic tRNA introns disrupt the anticodon stem-loop structure, the removal of these introns is an essential process.

In our lab, we aim to comprehend the structure and function of the eukaryotic tRNA splicing machinery. The mechanistic and structural insights will provide a comprehensive picture of how tRNA splicing enzymes function in the cell.
RNA Repair
While there is a substantial understanding for the various RNA maturation and degradation pathways, much less attention has been given to RNA repair and quality control. RNA can be subjected to damage through non-enzymatic hydrolysis or the action of endonucleases. These RNA cleavage events can be “sealed” by RNA ligases, which catalyse the ligation via phosphodiester bonds. We aim to uncover new RNA repair and quality control pathways based on these enzymes.
Our Approach
Using an interdisciplinary approach from protein and RNA biochemistry to structural biology and yeast genetics, we analyse the machinery and mechanisms that maintain RNA integrity. We often start by in vitro reconstitution of enzyme complexes, to determine their structure-function relationships. Once we purified protein, we study it using x-ray crystallography, cryo-electron microscopy (cryo-EM) as well as biophysical and biochemical methods. We explore the cellular role of RNA processing enzymes in the yeast Saccharomyces cerevisiae and mammalian cells.