Transposable elements (TEs) are major components of the human genome constituting at least half of it. More than half a century ago, Barbara McClintock and later Roy Britten and Eric Davidson have postulated that they might be major players in the host gene regulation. We have scanned a large amount of data produced by ENCODE project for active transcription binding sites (TFBSs) located in TE-originated parts of polymerase II promoters. In total, more than 35,000 promoters in six different tissues were analyzed and over 26,000 of them harbored TEs. Moreover, these TEs usually provide one or more of TFBSs in the host promoters, which resulted in more than 6% of active TFBSs in these regions located in the TE-originated sequences. Rewiring of transcription circuits played a major role in mammalian evolution and consequently increased their functional and morphological diversity. In this large-scale analysis, we have demonstrated that TEs contributed a large fraction of human TFBSs. Interestingly, these TFBSs usually act in a tissue-specific manner. Thus, our study clearly showed that TEs played a significant role in shaping expression pattern in mammals and humans in particular. Furthermore, since several TE families are still active in our genome, they continue to influence not only our genome architecture but also gene functioning in a broader sense.
Keywords: ENCODE project; gene expression evolution; genome evolution; promoters; transcription binding sites; transcription factors; transposable elements.