The long extra arms of human tRNA(Ser)Sec and tRNASer function as major identity elements for serylation in an orientation-dependent, but not sequence-specific manner

摘要

Selenocysteine tRNA [tRNA(Ser)Sec] is charged with serine by the same seryl-tRNA synthetase (SerRS) as the canonical serine tRNAs. Using site-directed mutagenesis, we have introduced a series of mutations into human tRNA(Ser)sec and tRNASer in order to study the identity elements of tRNA(Ser)Sec for serylation and the effect of the orientation of the extra arm. Our results show that the long extra arm is one of the major identity elements for both tRNASer and tRNA(Ser)Sec and gel retardation assays reveal that it appears to be a prerequisite for binding to the cognate synthetase. The long extra arm functions in an orientation-dependent, but not in a sequence-specific manner. The discriminator base G73 is another important identity element of tRNA(Ser)Sec, whereas the T- and D-arms play a minor role for the serylation efficiency.