Transfer RNA Processing and Disease
Transfer RNAs (tRNAs) are among the most ubiquitous molecules in cells from all three domains of life and central to decoding information from messenger RNAs to proteins on translating ribosomes. Beyond their canonical role during protein biosynthesis, tRNAs also perform additional functions as signaling molecules in the regulation of numerous metabolic and cellular processes, as stress sensors and in tRNA-dependent biosynthetic pathways. tRNA fragments have been identified as novel non-coding RNAs contributing to translational control, gene regulation and silencing. tRNAs are encoded as precursor molecules, which undergo a plethora of modifications, including removal of intronic sequences. In humans, introns are cleaved by the heterotetrameric tRNA splicing endonuclease (TSEN), which associates with the RNA kinase CLP1. Mutations in TSEN subunits or CLP1 lead to the development of severe neurological disorders, like pontocerebellar hypoplasia (PCH). PCH belongs to neurodegenerative autosomal recessive disorders with prenatal onset, causing hypoplasia of the cerebellum and ventral pons, microcephaly, and severe mental impairments. How PCH mutations engage in the development of the disease, whether there are moonlighting activities of TSEN towards yet unidentified substrates, or what the exact role of CLP1 in the process of pre-tRNA splicing is unclear. We address these fundamental questions on pre-tRNA processing by interdisciplinary and complementary approaches from cell and structural biology to biochemical and biophysical techniques.