Identification of factors that promote biogenesis of tRNA_CGA^Ser

A wide variety of factors are required for the conversion of pre-tRNA molecules into the mature tRNAs that function in translation. To identify factors influencing tRNA biogenesis, we previously performed a screen for strains carrying mutations that induce lethality when combined with a <i>sup61-T47:2C</i> allele, encoding a mutant form of tRNACGASer. Analyzes of two complementation groups led to the identification of Tan1 as a protein involved in formation of the modified nucleoside <i>N</i>⁴-acetylcytidine (ac⁴C) in tRNA and Bud13 as a factor controlling the levels of ac⁴C by promoting <i>TAN1</i> pre-mRNA splicing. Here, we describe the remaining complementation groups and show that they include strains with mutations in genes for known tRNA biogenesis factors that modify (<i>DUS2, MOD5</i> and <i>TRM1</i>), transport (<i>LOS1</i>), or aminoacylate (<i>SES1</i>) tRNACGASer. Other strains carried mutations in genes for factors involved in rRNA/mRNA synthesis (<i>RPA49, RRN3</i> and <i>MOT1</i>) or magnesium uptake (<i>ALR1</i>). We show that mutations in not only <i>DUS2, LOS1</i> and <i>SES1</i> but also in <i>RPA49, RRN3</i> and <i>MOT1</i> cause a reduction in the levels of the altered tRNACGASer. These results indicate that Rpa49, Rrn3 and Mot1 directly or indirectly influence tRNACGASer biogenesis.