Practical strategies for discovering regulatory DNA sequence motifs

MacIsaac KD, Fraenkel E


Many functionally important regions of the genome can be recognized by searching for sequence patterns, or “motifs.” Aside from the genes themselves, examples include CpG islands, often present in promoter regions, and splice sites that denote intron/exon boundaries. Other motifs of great interest correspond to sites bound by regulatory proteins. Differential expression of genes in response to environmental and developmental cues depends on the action of these proteins, which are also known as transcription factors. Identifying the regulatory motifs bound by transcription factors can provide crucial insight into the mechanisms of transcriptional regulation. However, the search for these sites is challenging because a single regulatory protein will often recognize a variety of similar sequences. In this tutorial, we review computational techniques, termed “motif discovery,” to learn representations of regulatory motifs from sequence data. In Figure 1, we present an overview of the basic workflow in a motif discovery analysis and some practical strategies for successfully mining sequence data for biologically important regulatory motifs. In the remainder of this tutorial, we discuss the main challenges associated with motif discovery in detail, and we review recent developments for addressing these challenges.

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