tRNASec is transcribed by RNA polymerase II in Trypanosoma brucei but not in humans.

摘要: Nuclear-encoded tRNAs are universally transcribed by RNA polymerase III (Pol-III) and contain intragenic promoters. Transcription of vertebrate tRNA(Sec) however requires extragenic promoters similar to Pol-III U6 snRNA. Here, we present a comparative analysis transcription in humans the parasitic protozoa Trypanosoma brucei, two evolutionary highly diverged eukaryotes. RNAi-mediated ablation Pol-II as well oligo-dT induced termination show that human is transcript. In T. brucei protein-coding genes polycistronically processed trans-splicing polyadenylation. tRNA generally clustered between polycistrons. However, trypanosomal embedded within polycistron. Their sensitive α-amanitin Pol-II, but not Pol-III. Ectopic expression outside inside polycistron an added external promoter. These experiments demonstrate tRNA(Sec), contrast its counterpart, Pol-II. Synteny shows trypanosomatids gene can be found different polycistrons, suggesting it has evolved twice independently. Moreover, intron-encoded number eukaryotic genomes indicating may restricted trypanosomatids.