The Saccharomyces cerevisiae TAN1 gene is required for N 4-acetylcytidine formation in tRNA

Abstract

The biogenesis of transfer RNA is a process that requires many different factors. In this study, we describe a genetic screen aimed to identify gene products participating in this process. By screening for mutations lethal in combination with a sup61-T47:2C allele, coding for a mutant form of tRNA CGASer, the nonessential TAN1 gene was identified. We show that the TAN1 gene product is required for formation of the modified nucleoside N4-acetylcytidine (ac4C) in tRNA. In Saccharomyces cerevisiae, ac4C is present at position 12 in tRNAs specific for leucine and serine as well as in 18S ribosomal RNA. Analysis of RNA isolated from a tan1-null mutant revealed that ac4C was absent in tRNA, but not rRNA. Although no tRNA acetyltransferase activity by a GST-Tan1 fusion protein was detected, a gel-shift assay revealed that Tan1 p binds tRNA, suggesting a direct role in synthesis of ac4C 12. The absence of the TAN1 gene in the sup61-T47:2C mutant caused a decreased level of mature tRNACGASer, indicating that ac4C12 and/or Tan1p is important for tRNA stability.