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Protein Phosphatase Sit4 Affects Lipid Droplet Synthesis and Soraphen A Resistance Independent of Its Role in Regulating Elongator Dependent tRNA Modification

Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil
Institut für Biologie, Fachgebiet Mikrobiologie, Universität Kassel, 34132 Kassel, Germany
Authors to whom correspondence should be addressed.
Biomolecules 2018, 8(3), 49;
Received: 4 June 2018 / Revised: 5 July 2018 / Accepted: 9 July 2018 / Published: 11 July 2018
(This article belongs to the Collection RNA Modifications)
PDF [4118 KB, uploaded 11 July 2018]


The protein phosphatase Sit4 has been shown to be required for lipogenesis and resistance against the acetyl-CoA carboxylase inhibitor soraphen A. Since Sit4 is also required for biosynthesis of Elongator dependent tRNA modifications such as 5-methoxycarbonylmethyluridine (mcm5U), we investigated the relevance of tRNA modifications in lipogenesis and soraphen A response. While sit4 and Elongator (elp3) mutants copy defects in mcm5U formation and stress sensitivity, they do not share soraphen A sensitivity and low lipid droplet (LD) phenotypes. In contrast to sit4, we found elp3 mutants to display partial soraphen A resistance and a high LD phenotype. Screening a collection of tRNA modification mutants additionally identified the tRNA pseudo-uridine synthase gene DEG1 to be required for soraphen A sensitivity. Since deg1 and elp3 share high LD and soraphen A resistance phenotypes, these are likely caused by translational defects. In support of this notion, we observe overexpression of tRNAGlnUUG suppresses lipolysis defects of deg1 mutants. Hence, the sit4 mutation results in a composite defect including tRNA modification deficiency and loss of Snf1 kinase dephosphorylation, which induce opposite effects on LD regulation. Importantly, however, the Snf1 kinase regulatory defects of the phosphatase mutant dominate over effects on LD regulation imposed by loss of the tRNA modification alone. View Full-Text
Keywords: soraphen A; Sit4; tRNA modification; Elongator complex soraphen A; Sit4; tRNA modification; Elongator complex

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Bozaquel-Morais, B.L.; Vogt, L.; D’Angelo, V.; Schaffrath, R.; Klassen, R.; Montero-Lomelí, M. Protein Phosphatase Sit4 Affects Lipid Droplet Synthesis and Soraphen A Resistance Independent of Its Role in Regulating Elongator Dependent tRNA Modification. Biomolecules 2018, 8, 49.

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