Increased transcription of NOP15, involved in ribosome biogenesis in Saccharomyces cerevisiae, enhances the production yield of RNA as a source of nucleotide seasoning.

Yeast RNA is a good source of nucleotide seasoning, and more than half of yeast RNA consists of ribosomal RNA (rRNA). Previously, we reported the development of a Saccharomyces cerevisiae strain displaying a 1.4- to 2.3-times higher RNA content than the wild-type strain through the isolation of dominant suppressors (designated SupA to SupG strains) from a Δrrn10 disruptant showing decreased rRNA transcription. In the present study, the cloning of one of the genes responsible for the suppression was attempted using a genomic library from the SupD strain. NOP15, a gene involved in ribosome biogenesis, was found to be responsible for suppressing the growth defect of the Δrrn10 disruptant. The isolated NOP15 allele (designated NOP15(T-279C)) possessed a single T to C substitution at nucleotide position-279 of NOP15. The transcription level of NOP15(T-279C) in the originally isolated SupD strain was 2-fold higher than that in the Δrrn10 disruptant. Furthermore, a dose-dependent relationship between the transcription level of NOP15 and total amount of RNA in the Δrrn10 disruptant was observed: the enhanced transcription due to the NOP15(T-279C) allele is involved in the suppression mechanisms in the SupD strain. Introduction of the NOP15(T-279C) allele into the wild-type strain increased the total RNA content by 1.4-fold. These results indicate that the transcription level of NOP15 is an important determinant of the productivity of RNA and that its increased transcription provides an effective approach to obtain higher RNA yields in yeast.