Fig. 5.

LkSki7 performs nonstop mRNA decay suboptimally, and sequence changes that disrupt Hbs1 function do not affect nonstop mRNA decay. (A) His3-nonstop growth assay demonstrating partial complementation by the L. kluyveri gene. Strains containing a his3-nonstop reporter were serially diluted and spotted onto media lacking (Left) or containing (Right) histidine. In cells with a wild-type SKI7 gene (Top row) the his3-nonstop mRNA is rapidly degraded, limiting the synthesis of histidine and therefore growth in the absence of histidine. In the ski7∆ strain (second row), a defect in nonstop mRNA decay results in growth. (B and C) Northern blot analyses of the degradation of a pgk1-nonstop mRNA. In both panels a representative blot is shown at Top, with quantitation and normalization to SRP RNA for three biological replicates shown at the Bottom. The bar graphs indicate average and SD.