Possibility of cytoplasmic pre-tRNA splicing: the yeast tRNA splicing endonuclease mainly localizes on the mitochondria.
Pre-tRNA splicing has been believed to occur in the nucleus. In yeast, the tRNA splicing endonuclease that cleaves the exon-intron junctions of pre-tRNAs consists of Sen54p, Sen2p, Sen34p, and Sen15p and was thought to be an integral membrane protein of the inner nuclear envelope. Here we show that the majority of Sen2p, Sen54p, and the endonuclease activity are not localized in the nucleus, but on the mitochondrial surface. The endonuclease is peripherally associated with the cytosolic surface of the outer mitochondrial membrane. A Sen54p derivative artificially fixed on the mitochondria as an integral membrane protein can functionally replace the authentic Sen54p, whereas mutant proteins defective in mitochondrial localization are not fully active. sen2 mutant cells accumulate unspliced pre-tRNAs in the cytosol under the restrictive conditions, and this export of the pre-tRNAs partly depends on Los1p, yeast exportin-t. It is difficult to explain these results from the view of tRNA splicing in the nucleus. We rather propose a new possibility that tRNA splicing occurs on the mitochondrial surface in yeast.
Yoshihisa
Tohru
T
Research Center for Materials Science, Nagoya University, Nagoya, 464-8602, Japan.
Yunoki-Esaki
Kaori
K
Ohshima
Chie
C
Tanaka
Nobuyuki
N
Endo
Toshiya
T
D003001:Cloning, Molecular; D004722:Endoribonucleases / Q000378:metabolism*; D017404:In Situ Hybridization, Fluorescence; D008928:Mitochondria / Q000378:metabolism*; D009154:Mutation; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism; D012322:RNA Precursors / Q000378:metabolism*; D012326:RNA Splicing; D012343:RNA, Transfer / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism
C408090:Los1 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D012322:RNA Precursors; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D012343:RNA, Transfer; D004722:Endoribonucleases; C051012:splicing endonuclease