Elongator function depends on antagonistic regulation by casein kinase Hrr25 and protein phosphatase Sit4.
In yeast, the role for the Elongator complex in tRNA anticodon modification is affected by phosphorylation of Elongator subunit Elp1. Thus, hyperphosphorylation of Elp1 due to inactivation of protein phosphatase Sit4 correlates with Elongator-minus phenotypes including resistance towards zymocin, a tRNase cleaving anticodons of Elongator-dependent tRNAs. Here we show that zymocin resistance of casein kinase hrr25 mutants associates with hypophosphorylation of Elp1 and that nonsense suppression by the Elongator-dependent SUP4 tRNA is abolished in hrr25 or sit4 mutants. Thus changes that perturb the evenly balanced ratio between hyper- and hypophosphorylated Elp1 forms present in wild-type cells lead to Elongator inactivation. Antagonistic roles for Hrr25 and Sit4 in Elongator function are further supported by our data that Sit4 inactivation is capable of restoring both zymocin sensitivity and normal ratios between the two Elp1 forms in hrr25 mutants. Hrr25 binds to Elongator in a fashion dependent on Elongator partner Kti12. Like sit4 mutants, overexpression of Kti12 triggers Elp1 hyperphosphorylation. Intriguingly, this effect of Kti12 is blocked by hrr25 mutations, which also show enhanced binding of Kti12 to Elongator. Collectively, our data suggest that rather than directly targeting Elp1, the Hrr25 kinase indirectly affects Elp1 phosphorylation states through control of Sit4-dependent dephosphorylation of Elp1.
Mehlgarten
Constance
C
Institut für Biologie, Genetik, Martin-Luther-Universität Halle-Wittenberg, Halle (Saale), Germany.
Jablonowski
Daniel
D
Breunig
Karin D
KD
Stark
Michael J R
MJ
Schaffrath
Raffael
R
D000935:Antifungal Agents / Q000494:pharmacology; D047389:Casein Kinase I / Q000235:genetics / Q000378:metabolism*; D018389:Codon, Nonsense; D025141:Drug Resistance, Fungal; D005786:Gene Expression Regulation; D016153:Genes, Suppressor; D051548:Histone Acetyltransferases / Q000378:metabolism*; D055646:Killer Factors, Yeast / Q000494:pharmacology; D009154:Mutation; D010445:Peptide Elongation Factors / Q000378:metabolism*; D010766:Phosphorylation; D014176:Protein Biosynthesis; D054648:Protein Phosphatase 2 / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013489:Suppression, Genetic
D000935:Antifungal Agents; D018389:Codon, Nonsense; D055646:Killer Factors, Yeast; D010445:Peptide Elongation Factors; D029701:Saccharomyces cerevisiae Proteins; C058975:zymocin; D051548:Histone Acetyltransferases; C479559:IKI3 protein, S cerevisiae; D047389:Casein Kinase I; C070775:HRR25 protein, S cerevisiae; D054648:Protein Phosphatase 2; C104343:SIT4 protein, S cerevisiae