AN EFFICIENTLY EXPRESSED 5.8S RIBOSOMAL-RNA TAG FOR IN-VIVO STUDIES OF YEAST RIBOSOMAL-RNA BIOSYNTHESIS AND FUNCTION

Inefficient expression or detrimental markers have limited mutational analyses of eukaryotic 5.88 rRNA and the associated rDNA transcribed s pacers. We have found a neutral, 4-base insertion mutation that effect ively tags the 5.8S rRNA for improved studies of rRNA expression, proc essing and function. Cells expressing the tagged rBNA plasmid contain 50-60% mutant 5.8S rRNA, but show a normal growth rate and polysomal p rofile and a constant distribution of tagged 5.8S rRNA. The high level of expression also demonstrates that plasmid-associated rDNA is prefe rentially transcribed over chromosomal copies.