Deletion of a subgroup of ribosome-related genes minimizes hypoxia-induced changes and confers hypoxia tolerance. Physiol Genomics 43: 855-872, 2011. First published May 17, 2011 doi:10.1152/physiolgenomics.00232.2010.-Hypoxia is a widely occurring condition experienced by diverse organisms under numerous physiological and disease conditions. To probe the molecular mechanisms underlying hypoxia responses and tolerance, we performed a genome-wide screen to identify mutants with enhanced hypoxia tolerance in the model eukaryote, the yeast Saccharomyces cerevisiae.Yeast provides an excellent model for genomic and proteomic studies of hypoxia. We identified five genes whose deletion significantly enhanced hypoxia tolerance. They are RAI1, NSR1, BUD21, RPL20A, and RSM22, all of which encode functions involved in ribosome biogenesis. Further analysis of the deletion mutants showed that they minimized hypoxia-induced changes in polyribosome profiles and protein synthesis. Strikingly, proteomic analysis by using the iTRAQ profiling technology showed that a substantially fewer number of proteins were changed in response to hypoxia in the deletion mutants, compared with the parent strain. Computational analysis of the iTRAQ data indicated that the activities of a group of regulators were regulated by hypoxia in the wild-type parent cells, but such regulation appeared to be diminished in the deletion strains. These results show that the deletion of one of the genes involved in ribosome biogenesis leads to the reversal of hypoxia-induced changes in gene expression and related regulators. They suggest that modifying ribosomal function is an effective mechanism to minimize hypoxia-induced specific protein changes and to confer hypoxia tolerance. These results may have broad implications in understanding hypoxia responses and tolerance in diverse eukaryotes ranging from yeast to humans.genome-wide screen; proteomic analysis; iTRAQ; regulatory network; stress response LIVING ORGANISMS RANGING FROM aquatic organisms to plants and humans can experience episodes of low oxygen availability, namely, hypoxia. Hypoxia can occur in plant roots when a field is flooded, in yeast during fermentation, or in humans at high altitudes or as a result of a heart attack or stroke. Because oxygen is critical for the survival and development of many living organisms, particularly eukaryotes, living organisms ranging from yeast to humans have developed sophisticated mechanisms to respond and adapt to the changes in oxygen levels in the environment (12, 127). In the wilderness, several species, including fossorial mammals, diving animals, and birds living at high altitudes, have acquired hypoxia tolerance, which enables them to survive under conditions of limited oxygen supply (9, 84, 92). In humans, hypoxia is associated with an array of pathological conditions, such as cancer and stroke. Mechanisms of oxygen sensing and regulation have been implicated in a wide array of physiological and pathological processes (35,99,127). Thus, studying hypoxia ...