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rRNA fragmentation induced by a yeast killer toxin
Author(s) -
Kast Alene,
Klassen Roland,
Meinhardt Friedhelm
Publication year - 2014
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12481
Subject(s) - biology , transfer rna , rnase p , saccharomyces cerevisiae , rna , protein subunit , ribosomal rna , nuclease , microbiology and biotechnology , yeast , genetics , dna , gene
Summary Virus like dsDNA elements ( VLE ) in yeast were previously shown to encode the killer toxins PaT and zymocin, which target distinct tRNA species via specific anticodon nuclease ( ACNase ) activities. Here, we characterize a third member of the VLE ‐encoded toxins, PiT from P ichia inositovora , and identify PiOrf 4 as the cytotoxic subunit by conditional expression in S accharomyces cerevisiae . In contrast to the tRNA targeting toxins, however, neither a change of the wobble uridine modification status by introduction of elp3 or trm9 mutations nor tRNA overexpression rescued from PiOrf 4 toxicity. Consistent with a distinct RNA target, expression of PiOrf 4 causes specific fragmentation of the 25 S and 18 S rRNA . A stable cleavage product comprising the first ∼ 130 nucleotides of the 18 S rRNA was purified and characterized by linker ligation and subsequent reverse transcription; 3′‐termini were mapped to nucleotide 131 and 132 of the 18 S rRNA sequence, a region showing some similarity to the anticodon loop of tRNA Glu ( UUC ) , the zymocin target. PiOrf 4 residues Glu 9 and His 214, corresponding to catalytic sites Glu 9 and His 209 in the ACNase subunit of zymocin are essential for in vivo toxicity and rRNA fragmentation, raising the possibility of functionally conserved RNase modules in both proteins.