Abstract: Global transcript levels throughout the cell cycle have been characterized using microarrays in several species. We applied a new algorithm to simultaneously analyze expression data from multiple species. Our results indicate that the conservation in cyclic expression patterns is much larger than previously thought. More than 20% of cycling genes in budding yeast have cycling homologs in fission yeast and roughly 5% of cycling genes in each of four species have cycling homologs in all other species. Motif analysis for the conserved genes suggests regulatory mechanisms leading to the resulting sets. While only 16% of cycling yeast genes are essential, 45% of cycling yeast genes with conserved cycling homologs in all species are essential. Similar results are obtained for human cycling genes by analyzing RNAi data. The conserved genes are enriched for most of the important cell cycle functions indicating that they represent the core set of cycling genes.
