Figure 7.

Steady-state levels and half-life of Mps1 fusion proteins are unaffected by mutation of CDC37. (a) Steady-state levels of ProA-Mps1p were assessed in wild-type and cdc37-1 strains. AS231-2d and AS231-2b (Table I), which carry the integrated protein A–tagged allele of MPS1, were grown at 25°C and then shifted to 38°C for 4 and 8 h. ProA-Mps1p was detected in whole cell lysates using rabbit IgG as primary antibody. Protein levels were unaffected even after an 8-h incubation at the nonpermissive temperature. (b) The half-life of a pool of galactose-induced myc-Mps1p was monitored in wild-type (AS230-7a) and cdc37-1 (AS230-7b) strains upon shift to the nonpermissive temperature. Expression of the fusion protein was induced with galactose at 25°C for 6 h; glucose was then added to the culture to repress the promoter, and the culture was divided. Cells were incubated at 25 or 38°C and sampled every 15 min for 1 h. Lysates were made and myc-Mps1p detected with 9E10 antibody. No reduction in halflife is seen at the nonpermissive temperature.