Figure 5

Survey of nucleolar/ribosomal gene expression. Histograms of sets of pairwise Pearson correlation coefficients computed from vectors of gene expression ratios for gene pairs. The distributions of Pearson correlation coefficients (each obtained from the pairwise comparison of expression profiles of two genes) gives an impression of the global similarity of expression patterns in a group of genes. Random data would give a Pearson correlation coefficient distribution centered around 0 (no correlation). The more a distribution deviates towards +1 compared to a 0-centered bell shape, the more similar a group of genes is expressed across the whole expression compendium. Gene pairs were formed within or between the functional/evolutionarily-defined groups of genes that are under investigation here. (a) Correlation within all yeast genes. (b) Correlation within genes that do not encode nucleolar proteins. (c) Correlation within genes for nucleolar proteins. (d) Correlation within genes for ribosomal or ribosome-associated proteins. (e) Correlation within nucleolar genes that stem from archaea. (f) Correlation within nucleolar genes that do not stem from archaea. (g) Correlation within genes that encode 90S processosome components. (h) Correlation between genes for ribosome proteins and 90S processosome proteins. Note that the distributions for the ribosomal protein genes and the 90S processosome strongly deviate from the rather 0-centered distribution of 'all genes-versus-all gene' comparisons. However, the distribution for gene pairs in which one partner is a 90S processosome component and the other partner is a ribosomal component deviate much less from the random shape and, thus, indicate distinct expression programs.