Identifying cooperativity among transcription factors controlling the cell cycle in yeast - PubMed (original) (raw)

Identifying cooperativity among transcription factors controlling the cell cycle in yeast

Nilanjana Banerjee et al. Nucleic Acids Res. 2003.

Abstract

Transcription regulation in eukaryotes is known to occur through the coordinated action of multiple transcription factors (TFs). Recently, a few genome-wide transcription studies have begun to explore the combinatorial nature of TF interactions. We propose a novel approach that reveals how multiple TFs cooperate to regulate transcription in the yeast cell cycle. Our method integrates genome-wide gene expression data and chromatin immunoprecipitation (ChIP-chip) data to discover more biologically relevant synergistic interactions between different TFs and their target genes than previous studies. Given any pair of TFs A and B, we define a novel measure of cooperativity between the two TFs based on the expression patterns of sets of target genes of only A, only B, and both A and B. If the cooperativity measure is significant then there is reason to postulate that the presence of both TFs is needed to influence gene expression. Our results indicate that many cooperative TFs that were previously characterized experimentally indeed have high values of cooperativity measures in our analysis. In addition, we propose several novel, experimentally testable predictions of cooperative TFs that play a role in the cell cycle and other biological processes. Many of them hold interesting clues for cross talk between the cell cycle and other processes including metabolism, stress response and pseudohyphal differentiation. Finally, we have created a web tool where researchers can explore the exhaustive list of cooperative TFs and survey the graphical representation of the target genes' expression profiles. The interface includes a tool to dynamically draw a TF cooperativity network of 113 TFs with user-defined significance levels. This study is an example of how systematic combination of diverse data types along with new functional genomic approaches can provide a rigorous platform to map TF interactions more efficiently.

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Figures

Figure 1

Figure 1

Schematic diagram of the ChIP-based approach of identifying cooperativity. The promoters of the set of genes that show binding of both TFs A (TFA) and B (TFB) show a much higher EC score (0.22) than the promoters of the sets of genes that show binding to only TF A (0.05) or TF B (0.06). Therefore, TFs A and B are potentially cooperative.

Figure 2

Figure 2

Overlapping ORFs in ChIP, motif and expression analysis. ChIP-based and expression-based approaches appear to identify more experimentally established targets of Mcm1 and Fkh2 than the motif- and expression-based approach described in Pilpel et al. (3).

Figure 3

Figure 3

Motif scores and gene expression of ChIP-positive target genes of Mcm1 and Fkh2. The known targets (circled in red) fall in the upper right-hand corner. The genes that are close to the known target genes in expression and motif space are likely to be reliable additional targets of Mcm1 and Fkh2 compared with those genes with low correlation with core expression profile and low motif score.

Figure 4

Figure 4

User interface to get a TF combination’s target genes and their expression profiles.

Figure 5

Figure 5

User interface to dynamically generate a TF cooperativity network with user-defined significance values.

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