Finding motifs in the twilight zone

Motivation: Gene activity is often affected by binding transcription factors to short fragments in DNA sequences called motifs. Identification of subtle regulatory motifs in a DNA sequence is a difficult pattern recognition problem. In this paper we design a new motif finding algorithm that can detect very subtle motifs. Results: We introduce the notion of a multiprofile and use it for finding subtle motifs in DNA sequences. Multiprofiles generalize the notion of a profile and allow one to detect subtle patterns that escape detection by the standard profiles. Our MULTIPROFILER algorithm outperforms other leading motif finding algorithms in a number of synthetic models. Moreover, it can be shown that in some previously studied motif models, MULTIPROFILER is capable of pushing the performance envelope to its theoretical limits.