A role for the universal Kae1/Qri7/YgjD (COG0533) family in tRNA modification

Abstract

The YgjD/Kae1 family (COG0533) has been on the top-10 list of universally conserved proteins of unknown function for over 5 years. It has been linked to DNA maintenance in bacteria and mitochondria and transcription regulation and telomere homeostasis in eukaryotes, but its actual function has never been found. Based on a comparative genomic and structural analysis, we predicted this family was involved in the biosynthesis of N 6 -threonylcarbamoyl adenosine, a universal modification found at position 37 of tRNAs decoding ANN codons. This was confirmed as a yeast mutant lacking Kae1 is devoid of t 6 A. t 6 A À strains were also used to reveal that t 6 A has a critical role in initiation codon restriction to AUG and in restricting frameshifting at tandem ANN codons. We also showed that YaeZ, a YgjD paralog, is required for YgjD function in vivo in bacteria. This work lays the foundation for understanding the pleiotropic role of this universal protein family.

The Levels of a Universally Conserved tRNA Modification Regulate Cell Growth

“…mined that this enzyme is necessary for cell autonomous growth in Drosophila, as we previously showed for Tcs5 (Prpk) (23). Metazoans are composed of different cell types, therefore making the phenotype observed in tcs3 mutants even more complex than the ones observed in yeast and other unicellular organisms (15,16,18,21,50,51). However, in every case analyzed, the deficiency of these enzymes strongly impairs cellular growth and proliferation.…”

“…In addition, considering the particular limiting nature of the initiator tRNA for cell and animal growth (5,7) and as this tRNA is modified by t 6 A, we were prompted to investigate the impact of t 6 A in whole animal context using Drosophila. All previous studies on t 6 A function and synthesis have been performed in unicellular organisms or cells in culture (15)(16)(17)(18)(19)(20)(21). In this study, we address for the first time the role of t 6 A in a metazoan.…”

“…It stabilizes codon-anticodon interaction (13), suggesting that t 6 A might have a role regulating protein synthesis initiation. The modification was discovered over 40 years ago (14), but the enzymes involved in t 6 A synthesis were only identified and characterized in all domains of life in the last few years (15)(16)(17)(18)(19)(20)(21) and recently renamed (22). In yeast, components of the threonyl-carbamoyl transferase complex (TCTC, previously named KEOPS/EKC (kinase, endopeptidase and other proteins of small size/endopeptidase-like and kinase associated to transcribed chromatin) are required for t 6 A synthesis.…”

“…Tcs3p (Kae1p) and Tcs5p (Bud32p) are part of the TCTC complex. Mutation of either gene eliminates t 6 A in tRNA and cause strong slow-growth phenotypes (15). Recently, we showed that Prpk (p53-related protein kinase), the Drosoph-* This work was supported, in whole or in part, by National Institutes of Health Grant R01 GM70641 (to V. d. C-L.), FONDECYT (Fondo Nacional de Desarrollo Científico y Tecnoló gico) 1140522 and FONDAP (Fondo de Financiamiento de Centros de Investigació n en Á reas Prioritarias) 15090007 grants (to A. G.), and CONICYT (Consejo Nacional de Investigació n Científica y Tecnoló gica) Grant AT24121519 (to D. R.…”

NMR-based Structural Analysis of Threonylcarbamoyl-AMP Synthase and Its Substrate Interactions

“…By strengthening the codon/anticodon interaction and ribosome entry, t 6 A 37 is believed to participate in the maintenance of the translational reading frame. This is supported by the increase in translational frameshifts in cells lacking the ability to form t 6 A 37 (13)(14)(15). Recent studies of the t 6 A 37 biosynthesis pathway have identified the following four proteins in Escherichia coli that are necessary and sufficient for in vitro formation of the modification: TsaC, TsaD, TsaE, and TsaB, also known as YrdC, YgjD, YjeE, and YeaZ, respectively (16).…”