![]() ![]() However, cis-regulatory palindromes rarely have such perfectly inverted repeats and the sequences of the left and right half-site therefore differ in at least one base pair. In human languages, the inverted repeats in single-word palindromes have to be perfect in order to mean the same forward as backward (e.g. Cis-regulatory palindromes can also consist of an odd number of base pairs, which can make it difficult to judge from sequence alone whether the central bases are unbound spacer sequences or belong to the bound left and right half-sites (e.g. ‘noon’) or an odd number of letters (e.g. Note the TAAT homeodomain core motif repeat on the opposite DNA strand (5’ TAAT…ATTA 3’ and 3’ ATTA… TAAT 5’).ĭ: The right TAAT core motif repeat is disrupted in an imperfectly palindromic motif variant (TAAT…ATT C instead of TAAT…ATT A), which recruits a different transcription factor type (red) and results in the binding of a heterodimer. The transcription factor controls where, when, and at which levels the gene is expressed.ī: The ‘Sator square’ is a complex square palindrome that consists of five Latin words (‘sator arepo tenet opera rotas’) that can be read top-to-bottom, bottom-to-top, left-to-right, and right-to-left (image from ).Ĭ: A homeodomain transcription factor (purple) binds as a homodimer to a palindromic cis-regulatory motif. Lastly, we propose to elucidate whether specific imperfectly palindromic variants have specific regulatory functions in steroid receptor signaling and whether such variants can help predict transcriptional outcomes as well as the response of individual patients to drug treatments.Ī: The schematic represents the binding of a sequence-specific transcription factor to a cis-regulatory motif in the regulatory DNA of a target gene. Moreover, we discuss mechanistic explanations for the predominance of imperfect palindromes over perfect palindromes in these two gene regulatory contexts. Here, we review the use of imperfect palindromes in Drosophila photoreceptor differentiation and mammalian steroid receptor signaling. the repeated sequences differ in at least one base pair, but the functional significance of this asymmetry remains poorly understood. Regulatory palindromes are typically imperfect, i.e. In regulatory DNA, a palindrome is an inverted sequence repeat that allows a transcription factor to bind as a homodimer or as a heterodimer with another type of transcription factor. In human languages, a palindrome reads the same forward as backward (e.g. ![]()
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