Since we have observed here that proteasome inhibitor PS341 treatment upregulates miR-30b-5p and miR-30c-5p in both normal and cancer cells and these miRs can target and decrease eIF2α, our findings also unveil a previously undocumented feedback mechanism by which impaired protein degradation suppresses general protein synthesis in the cell so that cellular proteostasis can be maintained at least temporarily. This evidence concerns the gene EIF2A and cancer.