DELETION OF A SINGLE-COPY TRANSFER-RNA AFFECTS MICROTUBULE FUNCTION IN SACCHAROMYCES-CEREVISIAE

rts1-1 was identified as an extragenic suppressor of tub2-104, a cold- sensitive allele of the sole gene encoding P-tubulin in the yeast, Sac charomyces cerevisiae. In addition, rts1-1 cells are heat sensitive an d resistant to the microtubule-destabilizing drug, benomyl. The rts1-1 mutation is a deletion of approximately 5 kb of genomic DNA on chromo some X that includes one open reading frame and three tRNA genes. Diss ection of this region shows that heat sensitivity is due to deletion o f the open reading frame (HIT1). Suppression and benomyl resistance ar e caused by deletion of the gene encoding a tRNA(AGG)(Arg) (HSX1). Nor thern analysis of rts1-1 cells indicates that HSX1 is the only gene en coding this tRNA. Deletion of HSX1 does not suppress the tub2-104 muta tion by misreading at the AGG codons in TUB2. It also does not suppres s by interfering with the protein arginylation that targets certain pr oteins for degradation. These results leave open the prospect that thi s tRNA(AGG)(Arg) plays a novel role in the cell.