Another heritage from the RNA world: self-excision of intron sequence from nuclear pre-tRNAs.
The intervening sequences of nuclear tRNA precursors are known to be excised by tRNA splicing endonuclease. We show here that a T7 transcript corresponding to a pre-tRNA(Tyr) from Arabidopsis thaliana has a highly specific activity for autolytic intron excision. Self-cleavage occurs precisely at the authentic 3'-splice site and at the phosphodiester bond one nucleotide downstream of the authentic 5'-splice site. The reaction results in fragments with 2',3'-cyclic phosphate and 5'-OH termini. It is resistant to proteinase K and/or SDS treatment and is not inhibited by added tRNA. The self-cleavage depends on Mg2+ and is stimulated by spermine and Triton X-100. A set of sequence variants at the cleavage sites has been analysed for autolytic intron excision and, in parallel, for enzymatic in vitro splicing in wheat germ S23 extract. Single-stranded loops are a prerequisite for both reactions. Self-cleavage not only occurs at pyrimidine-A but also at U-U bonds. Since intron self-excision is only about five times slower than the enzymatic intron excision in a wheat germ S23 extract, we propose that the splicing endonuclease may function by improving the preciseness and efficiency of an inherent pre-tRNA self-cleavage activity.
Weber
U
U
Institut für Biochemie, Bayerische Julius-Maximilians-Universität, Biozentrum, Würzburg, Germany.
Beier
H
H
Gross
H J
HJ
D017360:Arabidopsis / Q000235:genetics*; D017123:Bacteriophage T7 / Q000235:genetics; D001483:Base Sequence; D002384:Catalysis; D007438:Introns; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012322:RNA Precursors / Q000737:chemistry / Q000378:metabolism*; D012326:RNA Splicing; D018749:RNA, Plant / Q000737:chemistry / Q000378:metabolism*; D012365:RNA, Transfer, Tyr / Q000737:chemistry / Q000378:metabolism*; D013329:Structure-Activity Relationship
D012322:RNA Precursors; D018749:RNA, Plant; D012365:RNA, Transfer, Tyr; C030449:pre-tRNA(Tyr)