An efficiently expressed 5.8S rRNA 'tag' for in vivo studies of yeast rRNA biosynthesis and function

Inefficient expression or detrimental markers have limited mutational analyses of eukaryotic 5.8S rRNA and the associated rDNA transcribed spacers. We have found a neutral, 4-base insertion mutation that effectively tags the 5.8S rRNA for improved studies of rRNA expression, processing and function. Cells expressing the tagged rDNA plasmid contain 50-60% mutant 5.8S rRNA, but show a normal growth rate and polysomal profile and a constant distribution of tagged 5.8S rRNA. The high level of expression also demonstrates that plasmid-associated rDNA is preferentially transcribed over chromosomal copies.