The yeast transcriptome in aerobic and hypoxic conditions: effects of hap1, rox1, rox3 and srb10 deletions

The transcriptome of Saccharomyces cerevisiae was screened using the high-density membrane hybridization method, under aerobic and hypoxic conditions, in wild-type and mutant backgrounds obtained by the disruption of the genes encoding the regulatory proteins Hap1, Rox1 and the Srb10 and Rox3 subunits of RNA polymerase II holoenzyme. None of the mutations studied was able to fully overcome the wild-type hypoxic response. Deletion of the hap1 gene changed the expression profiles of individual open reading frames (ORFs) under both aerobic and hypoxic conditions. Major changes associated with rox3 deletion were related to the hypoxic activation. Rox3 also caused a repressor effect (oxygen-independent) on a subset of genes related to subtelomeric proteins. With regard to the effect brought about by the deletion of rox1 and srb10, correspondence cluster analysis revealed that the transcriptome profile in aerobic conditions is very similar in the wild-type and both deletion strains. In contrast, however, differences were found during hypoxia between the subgroup formed by wild-type and the Deltarox1 deletant compared with the Deltasrb10 deletant. An analysis of selected ORFs responding to hypoxia, in association with a dependence on the regulatory factors studied, made it possible to identify the clusters that are related to different regulatory circuits.