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Figure 3 | BMC Systems Biology

Figure 3

From: Functional redundancy of transcription factors explains why most binding targets of a transcription factor are not affected when the transcription factor is knocked out

Figure 3

High expression level and ribosomal genes are associated with high overlap percentage. The set of lowly/highly expressed genes is defined as those genes whose expression levels are among the bottom/top X% of the 4065 genes under study. By using the one-sided two-sample proportion test [28], we find that lowly expressed genes show significantly (p-value << 0.001) lower overlap percentage compared with highly expressed genes, suggesting that low expression level is associated with a gene being insensitive to the knockout of its promoter-binding TFs. Note that our result is robust against different choices (10, 20, 30, 40 or 50) of X and different sources ((a) Holstege et al.'s study [18] or (b) Nagalakshmi et al.'s study [19]) of gene expression data being used. The red line indicates the overlap percentage (4%) for all 4065 genes under study. In addition, ribosomal genes show significantly (using the one-sided two-sample proportion test) higher overlap percentage compared with the rest of 4065 genes under study. This result further supports our finding that highly expressed genes show significantly higher overlap percentage. Note that our result is robust against different sources ((c) KEGG [20] or (d) MIPS [17]) of the list of ribosomal genes being used.

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