The Kluyveromyces lactis γ-toxin targets tRNA anticodons

Abstract

Kluyveromyces lactis killer strains secrete a heterotrimeric toxin (zymocin), which causes an irreversible growth arrest of sensitive yeast cells. Despite many efforts, the target(s) of the cytotoxic g-subunit of zymocin has remained elusive. Here we show that three tRNA species tRNA . Transfer RNA lacking a part of or the entire mcm 5 group is inefficiently cleaved by g-toxin, explaining the g-toxin resistance of the modification-deficient trm9, elp1-elp6, and kti11-kti13 mutants. The K. lactis g-toxin is the first eukaryotic toxin shown to target tRNA.

Glutaredoxin GRXS17 Associates with the Cytosolic Iron-Sulfur Cluster Assembly Pathway

“…In the light of these findings, it is interesting to note that the GRX3 gene was identified previously as a high-copy suppressor in yeast of growth inhibition by zymocin, a fungal tRNase ribotoxin complex (Jablonowski et al, 2001;Jablonowski and Schaffrath, 2007). Zymocin activity targets elongator-dependent mcm 5 s 2 U34 modifications in tRNA anticodons (Lu et al, 2005;Jablonowski et al, 2006) and eventually kills S. cerevisiae cells. Therefore, loss of tRNA modification in elongator (elp) or tRNA methyltransferase (trm9) mutants protects against zymocin, making the tRNase a useful tool for diagnosing elongator function and, hence, tRNA modification in yeast (Nandakumar et al, 2008) and potentially in Arabidopsis (Mehlgarten et al, 2010;Leitner et al, 2015).…”

Elongator, a conserved complex required for wobble uridine modifications in Eukaryotes

“…41,42 The g-toxin turned out to be an endonuclease having tRNA 43 These tRNAs have the mcm 5 s 2 U modified nucleoside at wobble position and the endonuclease cleaves the tRNAs between U 34 and U 35 . 43 Presence of the mcm 5 side chain of mcm 5 s 2 U is crucial for these tRNAs to be substrates, explaining why Elongator mutants are resistant to zymocin or endogenously expressed g-toxin.…”

“…43 Presence of the mcm 5 side chain of mcm 5 s 2 U is crucial for these tRNAs to be substrates, explaining why Elongator mutants are resistant to zymocin or endogenously expressed g-toxin. 43,44 Thus, the g-toxin resistance phenotype as well as phenotypes of yeast Elongator mutants suppressed by overexpression of hypomodified tRNAs are explained by an inability to make mcm 5 and ncm 5 side chains at wobble uridines.…”

Increased tRNA modification and gene-specific codon usage regulate cell cycle progression during the DNA damage response

“…[1][2][3] Trm9-catalyzed tRNA modifications have been implicated in differentiating between cognate and near cognate codons in mixed codon boxes and optimizing codon-anticodon interactions. 1,4 Reporter studies support that Trm9-catalyzed tRNA modifications enhance binding to codons ending in A in arginine and glutamic acid mixed codon boxes to increase the speed of translation in a codon-dependent context.…”