Figure 2

Different RNA processing events in mammals. 2A: Eukaryotic splicing pathway of tRNA splicing in mammals. The TSEN complex is involved in the maturation of premature tRNAs and excises the tRNA into two halves; one 5'tRNA half with a 2'-3' cyclic phosphate at one exon-end and a 3'tRNA half with a 5'OH-group at the other exon-end. The final processing of tRNA maturation involves either direct ligation of the two tRNA halves by ligation through the Archaea-like pathway (by HSPC117, depicted) or indirect ligation through the yeast-like pathway (not depicted) [104]. Adapted from Calvin et al. [105]. 2B: tRNA aminoacylation in mammals. RARS2 can bind to its cognate amino acid in an ATP dependent matter. This complex of ATP, RARS2 and arginine binds to the mt-tRNA-Arg and arginine will be transferred to its tRNA. Adapted from Antonellis et al. [83]. 2C: Selenocysteine synthesis. Serine (Ser) is aminoacylated to tRNA-Sec by a seryl-tRNA synthetase (SARS). This Ser-tRNA-Sec complex is then converted by a kinase to a Sep-tRNA-Sec complex. In the presence of the cofactor pyridoxal phosphate (PLP) and the selenium donor selenophosphate (Se-donor) the SEPSECS enzyme converts the Sep-tRNA-Sec to Sec-tRNA-Sec. Adapted from Allmang et al. [87].